Chapter I: Part 1

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CATALOGUE No. 40.

MICROSCOPES
AND
ACCESSORY APPARATUS.

ERNST LEITZ
WETZLAR
GERMANY.

Founded in 1850.

Branch Offices:
NEW-YORK: CHICAGO: BERLIN NW.
411 West 59th Str. 32-38 Clark Str. 45 Luisenstrasse.
30 East 18th Street.

1903.

="Highest award"= Worlds Columbian Exhibition =Chicago 1893=.

Contents.

New constructions 5
Objectives and Eye-pieces 7
Stands 16
Illuminating Apparatus 20
Complete Microscope Outfits 24
Microscopes for Mineralogical Research 57
Dissecting Microscopes and Lupes 62
Apparatus for Blood Examinations 70
Micrometers 73
Drawing Apparatus 74
Mechanical Stages 78
Photo-micrographic Apparatus 82
Projection Apparatus (Edinger) 84
The Large Projection Apparatus 87
Microtomes 92
Miscellaneous Accessories 99
Publications 104
Index 105

Notice.

All previous editions of this catalogue are superceded by the present one, which should be exclusively used in ordering.

Orders will be filled at once after their receipt.

In ordering care should be taken to give the =number= of each article desired and to state listprice.

To avoid delay and misunderstandings, we request that name and address be plainly written.

Goods are forwarded at the expense and risk of the purchaser.

Our instruments for use in =Universities, Colleges, Schools= &c. of the =United States= are by law free of duty and we shall be pleased to make specially low quotations for such orders.

ERNST LEITZ.

New Constructions.

Since issueing our last catalogue, a number of new apparatus and accessories have been added. The following are the more important ones:

1. A completely =new stand "A"= with extra fine micrometerscrew transmitting its movement directly to the tube. The stand is of elegant appearance and large dimensions, making it especially well adapted for work in photo-micrography.

2. =Stand I= is now fitted out with the new special fine adjustment (each division {1/1000} mm).

3. =Stand II= with round centering stage.

4. =Stand IV= is replaced by a model of larger size.

5. =Photo-micrographic apparatus= for use in horizontal and vertical position, having joint for inclination, large size bellows and plateholder.

6. =Large projection-apparatus= for electric lamp of 30 Ampère with triple collecting lens of 210 mm aperture.

7. =Objective 1 a= with adjustable mounting and changeable magnification. It is an excellent objective of low power for general purposes, having a comparatively short working distance.

8. =Objective 1 b= with changeable magnification of lowest power, as far down as two diameters. It serves for drawing extended sections and specimens.

9. =Saccharimeter after Mitcherlich= improved form.

10. =Trichinoscope=, projection-apparatus of strong and simple construction.

=Preface.=

Our American Branch house in New-York under the management of Mr. Wm. Krafft has now been established for over 10 years. This period has witnessed a gradual development of our business in the United States, making it necessary to establish some years ago a Western Branch in Chicago of which Mr. R. Gibson has charge.

The cordial reception our firm received has been most gratifying and we take this opportunity to thank our many patrons for their kind consideration.

It is our aim to co-operate with the scientists and construct new apparatus to meet their needs or improve others wherever this is possible.

The foregoing list of additions and improvements made since issueing our last catalogue is proof that we spare no time nor labor to hold pace with the increased wants of modern times.

We have now manufactured and sold over 71000 compound microscopes and 31000 oil immersion objectives, a large number of which are used in the laboratories of Universities, Colleges, and other Educational Institutions of the United States.

We are prepared at New-York and Chicago to repair our instruments or make alterations at short notice and at lowest prices. The optical part of a microscope should invariably be sent to the maker, as he is best in a position to repair same and has an added interest to bring a lens back to its original quality or even improve it.

Microscopes, bacteriological apparatus and all other scientific instruments or preparations expressly imported for use in educational institutions are exempt from duty.

Catalogues may be had on application by addressing:

=ERNST LEITZ,=

NEW-YORK CHICAGO
411 West 59th Street 32 Clark, Cor. Lake Street.

=Objectives and Eye-pieces.=

In the manufacture of our objectives only such glass is employed as has been subjected to the most rigid scientific tests. By these the exact index of refraction and the exact degree of dispersion of the glass are determined, and with these data available it is possible to very perfectly correct both spherical and chromatic aberrations while still making use of wide angular apertures in the objectives.

The precise mathematical calculation, combined with accurate systematical working and testing methods, make it possible for us to guarantee our objectives to be all of equal and excellent quality.

Every objective before leaving our hands, is subjected to the most careful test, and only such lenses as are of the highest grade, are sent out.

For the past seventeen years we have used glasses manufactured by Schott & Co. of Jena. This glass has many points to recommend it for the construction of optical instruments, and only such kinds are employed by us, which have for many years been thoroughly tested as to their durability.

Our lenses are therefore absolutely permanent. Objectives of the earlier type which have become cloudy, we shall gladly repair.

The three illustrations given above afford an idea of the plan of construction of our achromatic objectives.

The first figure represents the plan of our low power objectives, and it will be noted that they consist of two doublets, or triplets each carefully corrected.

The central figure shows the construction of our high power dry objectives. A hemispherical front lens is combined with two doublets or sometimes triplets. The front lens is the chief magnifier of the combination, while the other lenses serve to correct the various aberrations.

The Oil-immersion, represented by the last illustration consists of a front lens, hemispherical, behind which is a meniscus, which is in turn followed by a doublet and a triplet, these latter acting as the correcting lenses of the combination.

We manufacture both =Achromatic= and =Apochromatic objectives=. They differ in that the glasses made use of in the apochromatics and the manner in which they are combined permit a more perfect correction of chromatic aberration. This advantage is not gained without a certain sacrifice of simplicity in construction; by avoiding the use of flint glass having a high refractive index and substituting materials to take the place of crownglass. The apochromatics as a matter of fact do resolve the fine markings of test objects (butterfly scales and diatomes) somewhat more clearly than the achromatics, but the difference is slight and in ordinary stained microscope preparations is hardly detectable.

The correction of both achromatics and apochromatics is complete. The ordinary Huyghenian eye-pieces are consequently well adapted for use with the objectives of either construction. Only with the highest powers is it desirable to make use of the so-called "compensation" eye-pieces.

The achromatics and Huyghenian eye-pieces are also well adapted to the requirements of photomicrography, special objectives being unnecessary for this purpose. This statement is substantiated by the excellent results obtained with our achromatic objectives, as shown in the photomicrographs accompanying our brochure on Photomicrography:--"Anleitung zur Mikrophotographie".

In making use of the higher power objectives--from No. 5 on--it should be remembered, that the lenses are corrected for cover glasses of 0,17 mm in thickness and for a microscope tube-length of 170 mm. When using the oil-immersion objectives it is particularly desirable, that this exact tube length should be employed. With a view to facilitate the adjustment of the tube-length the draw tubes of all our larger stands are graduated in millimeters, the scale indicating the exact length of the microscope tube in any given position of the draw tube. In this connection it should be remembered, that the width of the collar of the nose-pieces is 15 millimeters, and that consequently, when a nose-piece is attached to the tube the reading of the draw tube scale should be 155 mm instead of 170 when the adjustment is proper.

The above sketch may serve to make clear the advantages of the immersion objectives over those of the dry series. It is intended to represent diagrammatically a section through a cover-glass and the front lens of an objective, one half of the figure representing the conditions present in the case of the Oil-immersion, the other those which are present in the dry objectives. It will be noticed that by the interposition of a drop of oil of the same index of refraction as the glass between the cover-glass and the objective the refraction which occurs in the dry system when the light leaves the upper surface of the cover-glass is done away with. Since this second refraction is attended with much loss of light it must be evident, that in the immersion system a much greater quantity of light enters the objective than is possible, other things being equal, in objectives of the dry system.

If we let _u_ represent one half the angular aperture of an objective, represented in the diagram by _D'BN_ in the case of the immersion, and _n_ the index of refraction of the medium interposed between the cover-glass and the objective we have in the formula _n_ sin. _u_ a mathematical expression of the optic power of the various systems of lenses, or in other words for what is designated the numerical aperture.

The following table gives the numerical apertures of objectives of the various systems and of various angular apertures. In the dry system _n._, representing the index of refraction of air is taken as 1.00; in the immersion systems _n_ equals 1.33 for water, 1.52 for cedar oil and 1.66 for monobromnaphthalin. A glance at the table will suffice to show the great advantage which the immersion objectives have over those of the dry series.

--------------+----+----+----+----+----+----+----+----+----+----+----+----+----+----
Angular |10° |20° |30° |40° |50° |60° |70° |80° |90° |100°|110°|120°|130°|140°
aperture 2 _u_| | | | | | | | | | | | | |

=Numerical apertures.=

--------------+----+----+----+----+----+----+----+----+----+----+----+----+----+----
Dry series |0,09|0,18|0,26|0,34|0,42|0,50|0,57|0,64|0,71|0,77|0,82|0,87|0,91|0,94
_n_ = 1,00 | | | | | | | | | | | | | |
--------------+----+----+----+----+----+----+----+----+----+----+----+----+----+----
Water- | | | | | | | | | | | | | |
Immersion |0,12|0,24|0,35|0,46|0,56|0,66|0,76|0,85|0,94|1,02|1,09|1,15|1,20|1,25
_n_ = 1,33 | | | | | | | | | | | | | |
--------------+----+----+----+----+----+----+----+----+----+----+----+----+----+----
Homogeneous | | | | | | | | | | | | | |
Oil-Immersion |0,14|0,26|0,40|0,52|0,64|0,76|0,87|0,98|1,07|1,16|1,24|1,32|1,38|1,43
_n_ = 1,52 | | | | | | | | | | | | | |
--------------+----+----+----+----+----+----+----+----+----+----+----+----+----+----
Monobromide of| | | | | | | | | | | | | |
Naphthaline- | | | | | | | | | | | | | |
Immersion |0,15|0,29|0,43|0,57|0,70|0,83|0,95|1,07|1,17|1,27|1,36|1,44|1,50|1,56
_n_ = 1,66 | | | | | | | | | | | | | |

----------------+----+----+----+----
Focal length mm | 64 | 42 | 35 | 24
----------------+----+----+----+----
Price $ | 20 | 18 | 18 | 18
----------------+----+----+----+----

=Objective 1b.=

It is designed principally for drawing extended sections and large specimens, and consists of two adjustable doublets. By varying their distance, a changeable magnification down to two diameters may be obtained.

Price $ 8.--

=Huyghenian Eye-pieces.=
----------------+------+------+------+-------+------+------
Number | 0 | I | II | III | IV | V
----------------+------+------+----------------------------
Focal length mm | 50 | 40 | 35 | 30 | 25 | 20
----------------+------+------+----------------------------
Price of each eyepiece $ 2.00.

The objectives designed for the Edinger apparatus of 64, 42, 35, and 24 mm focal distance have been found to be very useful for a number of purposes and have come into great favor.

(see. Dr. Kaiserling: Praktikum der wissenschaftlichen Photographie p. 263).

=Achromatic Objectives.=

=============================================================================
| |Numerical | Micrometer | Price
No. of Objective|Focal length |Aperture | Values | $
| |(num. aper.)| |
--------------------------------+----------------------------+------------------------+--------------------------------+------------------------------
Low power { 1*|44 mm (1-3/4")| 0,09 | 0,054 mm = 54µ | =3.25=[1]
Dry { 1 |44 mm (1-3/4")| 0,09 | 0,054 mm = 54µ | =6=
Series { 1a| 39-27 mm | 0,06--0,10 | 50--26µ | =10= (adjustable
| | | | mounting)
{ 2 |30 mm (1-1/4")| 0,14 | 0,028 mm = 28µ | =6=
{ 3 |18 mm (3/4) | 0,28 | 0,015 mm = 16µ | =6=
{ 4 | 8 mm (1/3) | 0,55 | 0,009 mm = 9µ | =10=
----------------+----------------------------+------------------------+--------------------------------+------------------------------
High power { 5 |5,8 mm (1/4") | 0,77 |0,0045 mm = 4,5µ| =10=
{ 6 |4,4 mm (1/6") | 0,82 |0,0034 mm = 3,5µ| =12=
(Fluorite) { 6a|4,4 mm (1/6") | 0,82 |0,0034 mm = 3,5µ| =16=[2]
{ 7 |3,2 mm (1/8") | 0,85 |0,0026 mm = 2,6µ| =12=
(Fluorite) { 7a|3,2 mm (1/8") | 0,85 |0,0026 mm = 2,6µ| =16=[2]
" { 8 |2,5 mm (1/10")| 0,87 |0,0020 mm = 2,0µ| =16=
" { 9 |2,2 mm (1/12")| 0,87 |0,0017 mm = 1,7µ| =24=
----------------+----------------------------+------------------------+--------------------------------+------------------------------
Water- | | | |
Immersion 10|2,2 mm (1/12")| 1,10 |0,0017 mm = 1,7µ| =26=
----------------+----------------------------+------------------------+--------------------------------+------------------------------
Homogeneous{1/10|2,5 mm (1/10")| 1,30 |0,0022 mm = 2,2µ| =30=
Oil- {1/12|2,1 mm (1/12")| 1,30 |0,0017 mm = 1,7µ| =40=
Immersion {1/16|1,7 mm (1/16")| 1,30 |0,0014 mm = 1,4µ| =60=
=============================================================================

[Footnote 1: Objective 1* consists of only one doublet, carefully corrected. It is sufficient for many purposes, though it does not possess the same brilliancy of field as the No. 1 objective.]

[Footnote 2: The objectives 6a. and 7a. are better corrected in achromatism than the regular No. 6 and 7.]

=Magnification=
of the Achromatic and Apochromatic Objectives in combination with the
Huyghenian Eye-pieces.

Tube-length 170 mm. Distance of image 250 mm.

============================================================================
| Eye-pieces |
Objectives |-----------------------------------| Objectives
| 0 | I | II | III | IV | V |
--------------------------------------------------+----------+----------+----------+----------+----------+----------+----------------------------
{ 1* | 12 | 18 | 22 | 26 | 30 | 40 |
{ 1 | 12 | 18 | 22 | 26 | 30 | 40 |
Low Power { 1a | 6-9 | 9-15|11-19|13-21|18-29|24-35|
Objectives { 2 | 25 | 33 | 40 | 50 | 60 | 80 |
{ 3 | 45 | 60 | 70 | 80 | 105 | 130 |
{ 4 | 75 | 100 | 115 | 135 | 180 | 230 |
--------------------------------------------------+----------+----------+----------+----------+----------+----------|
High Power { 5 | 140 | 180 | 210 | 250 | 325 | 420 |
Objectives { 6 and 6a| 200 | 255 | 300 | 350 | 460 | 600 | Achromatics
(Cover-glass { 7 and 7a| 260 | 335 | 400 | 450 | 600 | 780 |
thickness { 8 | 300 | 400 | 450 | 550 | 700 | 940 |
0,17 mm) { 9 | 380 | 500 | 575 | 700 | 900 |1150 |
--------------------------------------------------+----------+----------+----------+----------+----------+----------|
Water-Immersion { 10 | 405 | 535 | 610 | 745 | 950 |1200 |
--------------------------------------------------+----------+----------+----------+----------+----------+----------|
Homogeneous { 1/10 | 310 | 415 | 470 | 575 | 730 | 940 |
Oil-Immersion { 1/12 | 435 | 555 | 650 | 800 |1000 |1300 |
{ 1/16 | 520 | 700 | 800 | 950 |1250 |1680 |
--------------------------------------------------+----------+----------+----------+----------+----------+----------+----------------------------
Dry { 16 | 45 | 60 | 70 | 85 | 110 | 140 |
Lenses { 8 | 95 | 125 | 145 | 170 | 225 | 295 | Apochromatics
{ 4 | 210 | 270 | 315 | 375 | 500 | 635 |
--------------------------------------------------+----------+----------+----------+----------+----------+----------|
Oil-Immersion 2 | 390 | 510 | 585 | 705 | 920 |1180 |
============================================================================

=Apochromatic Objectives.=

==================================================================
Objectives |Focal length|Numerical|Micrometer| Price
| mm | Aperture| Values | $
----------------------------------------------+------------------------+------------------+--------------------+----------------
{ 16 | 16 | 0,30 | 0,015 mm | =24=
Dry Series { 8 | 8 | 0,65 | 0,007 mm | =32=
{ 4 | 4 | 0,95 | 0,003 mm | =48=
| | | |with correction
| | | | collar
----------------------------------------------+------------------------+------------------+--------------------+----------------
Homogeneous { 2 | 2 | 1,30 | 0,002 mm | =100=
Oil-Immersion { | | | |
----------------------------------------------+------------------------+------------------+--------------------+----------------

Compensation Eye-pieces.
for Apochromatic Objectives.

=================================================
Eye-pieces | 4 | 6 | 8 | 12 | 18
--------------+------+------+------+------+------
Price $ |=6.50=|=6.50=| =10= | =10= | =8=
=================================================
Compensation Eye-piece 6 with micrometer =$8.50=

=Magnification=
of the Apochromatic Objectives in combination with the Compensation
Eye-pieces.

==================================================
| Eye-pieces
Objectives |-----+-----+-----+-----+-----
| 4 | 6 | 8 | 12 | 18
--------------------+-----+-----+-----+-----+-----
{ 16 | 70 | 100 | 125 | 155 | 225
Dry Series { 8 | 140 | 200 | 260 | 325 | 465
{ 4 | 300 | 430 | 550 | 675 |1000
--------------------+-----+-----+-----+-----+-----
Oil-Immersion 2 | 575 | 820 |1080 |1500 |2250
==================================================

Until very recently we have manufactured no arrangement for changing oculars on the microscope. This was due in part to the fact that there was no great demand for such an accessory and in part to the clumsiness of all those revolving eye-pieces which changed the entire ocular. The latter of these difficulties has been overcome in our present revolving eye-piece by such an adjustment of the collecting or lower lens of the eye-piece that it may remain permanently in position, the eye lens of the combination alone moving in the revolver. So accurate is the construction of the revolver and so carefully are the lenses adjusted that the eye-pieces may be changed while a specimen is in focus on the microscope stage without a readjustment of the focus.

The revolving eye-piece is also particularly well adapted to use as a micrometer ocular, for when the eye lens is turned aside a micrometer scale may be inserted and rests upon the diaphragm of the eye-piece. Once adjusted in this way the micrometer values are the same for all the eye lenses of the combination.

$
Prices: =Double revolving Eye-piece=, without eye lenses =4.--=
Each eye lens =1.25=
=Eye-piece Micrometer=, No. 86 =2.--=

=Stands.=

For the past thirty years division of labor has been employed to the utmost possible extent in the manufacture of our microscopes. This principle has been applied to our machinery as well as to our workmen, with the result that we have gradually accumulated a large plant of special machinery of the most accurate construction, each machine especially adapted to the manufacture of some particular part of our microscopes. By this development of mechanical appliances for microscope manufacture two ends have been attained:--The greatest accuracy and uniformity of construction of our microscopes has been made possible, while at the same time it has been possible to cheapen the cost of manufacture. Instruments which are the product of delicate machinery must always be more uniform, more accurate and should be less costly than those manufactured by hand.

In the following remarks we refer more particularly to the larger microscope stands of our manufacture and draw attention to those parts which should be present in every well equipped microscope.

The elements of these microscopes are:

1. =The foot and upright support with joint for inclination=,
2. =The stage=,
3. =The sub-stage, with condenser, iris diaphragm and mirror=,
4. =The body with the adjustments=,
5. =The tube, carrying eye-piece, nose-piece and objectives=.

1. =The foot and upright support= are solid and are of such weight and shape as to permit inclination of the body of the microscope to a horizontal position. The foot is horse-shoe shaped and is made to touch the table at three points, thus insuring stability even on a surface which is not entirely level. Inclination of the body of the microscope is permitted by a joint in the upright, which joint may be fastened in the larger stands by a set-screw operated by a lever. Stands Ia and IIb are also made with the English foot. Abundant space is left under the stage for the various attachments of the sub-stage.

2. =The stage= of Stands A, I, Ia and II is round, revolving and centering. The centering arrangement consists of two small thumb-screws so situated at the sides of the stage as to control motion of the stage in all directions, thus to a limited extent serving the purpose of a mechanical stage.

=The other microscope= stands have square immovable stages, sufficiently large for general microscopic work. For the examination of very large sections two instruments are manufactured: the _Nebelthau_ sliding microscope (p. 50) and the stand after _Dölken_ (p. 52). The former is for magnifications up to 120 diam, whereas the latter can be used with any magnification.

3. =The sub-stage= carries a plane and concave mirror, the condenser and the diaphragm for regulating the illumination of the object.

=The Condenser= is so adjusted as to concentrate the rays of light about 2 mm above its surface, which is the average thickness of the microscopic slides, under an angle equal to the angular aperture of the highest power objective, which is about 120°.

In the lower power objectives the angular aperture is to be reduced by the iris diaphragm.

To focus the Condenser properly it is adjustable by rack and pinion movement on Stands A, I, Ia, Ib, and by side screw on Stands II and IIa.

4. =The body= of the microscope carries the tube and is fitted with two adjustments for focussing; a coarse adjustment and a fine adjustment. The smooth working of these adjustments is one of the chief requirements of a good microscope.

=The coarse adjustment= consists of rack and pinion and moves the tube of the microscope in a vertical groove with the least possible friction. The teeth of the rack and pinion are set obliquely to the axis of the tube and are so adjusted that two teeth of each are always interlocked, thus avoiding all possibility of slipping or loss of motion in the movement.

=The fine adjustment= consists of a micrometer screw which moves the tube and arm of the microscope supporting the coarse adjustment vertically upon a triangular column. This column is virtually a continuation upward of the upright support of the base of the microscope. Around the column is a broad collar so accurately fitted that it moves smoothly upon it with a minimum of friction and still without lateral motion, the movement being controlled by means of a micrometer screw at the top of the column. The head of this micrometer screw, a section of which is shown in the accompanying figure, is milled and is graduated in such a way as to indicate the exact degree of motion of the microscope tube which is accomplished by turning the micrometer screw, each division of the graduation corresponding to a motion of the tube through 1/100 millimeter, and a complete revolution of the screw corresponding to a motion of the tube through ½ millimeter. The accuracy of this adjustment and the smoothness of its motion must be conceded to be a triumph of mechanical skill.

=Stands A.= and =I.= are fitted with a =new fine adjustment= device (one division on the micrometer screw corresponding to 1/1000 mm.) which is fully described on pages 25-26.

5. =The tube= of the microscope encloses a second tube, or draw-tube, which latter carries the eye-piece, and is so graduated as to indicate the exact length of tube in use at any time. The lower end of the tube has a thread into which the various objectives or a nose-piece screw. Tube and objectives are provided with the so-called "Society screw".

=The nose-piece= has now become an almost indispensable part of a working microscope. It can, however, be used to best advantage only on such stands as are provided with a coarse adjustment by rack and pinion. Aside from the advantage derived from the rapid changing of objectives, which it permits, it is so accurately made and centered as to materially facilitate the focussing of the various objectives. It is only necessary to focus with the fine adjustment to obtain a view of the same microscope field which had been under observation before the change was made.

As it is necessary for this purpose that the objectives should be accurately adjusted to the nose-piece, it is very desirable that in ordering an instrument its nose-piece should be ordered at the same time if one is to be used, as subsequent ordering may necessitate the return of the stand and objectives to us.

=Stands A, I, Ia, Ib, II, IIa, IIb and III= are those which are best suited to fine microscopical investigations. Among them the physician and bacteriologist will find an instrument entirely suited to his particular needs.

=Stand III= is now provided with rack and pinion adjustment.

=Stands IV and V= are small instruments, which serve nevertheless many purposes where the more elaborate outfits are unnecessary. They make excellent laboratory stands for elementary courses in microscopy.

In =Stands IV and V= the coarse adjustment is by means of sliding tube. They are all provided with fine adjustment by micrometer screw.

=Stand VI= is provided with rack and pinion adjustment only. It has a large stage, and is particularly intended for searching for trichinae and for similar examinations where a very strong durable stand is desired and where the use of high power objectives is unnecessary. It may also be useful as an auxiliary stand for purposes of demonstration in laboratories.

=Stands III, IV, V, VI= have no joint for inclining the body.

=Stands A, I, Ia, Ib, II, IIa, IIb, III, IV= have mahogany cases (provided with a nickelled handle), in which the microscopes stand.

=Stands V and VI= are laid in mahogany boxes.

These cases are furnished with the microscopes without extra charge, when a =complete outfit=, including oculars and objectives is purchased.

Object clamps and test objects accompany every microscope.

The objectives to Stands A, I, Ia, Ib, II, IIa, IIb are in brass boxes; those for Stands III, IV, V and VI are in morocco cases.

=Illuminating Apparatus.=

=a. Illuminating Apparatus of Stands A and I.=

The apparatus includes the following parts:

Cylinder iris diaphragm.
Swing-out condenser.
Diaphragm carrier with iris diaphragm.
Plane and concave mirror.

The cylinder iris diaphragm comes into play when the condenser is swung out of position. To do this the diaphragm carrier is turned to the side as shown in the diagram, a small knob is pressed, which liberates the condenser, and the latter is swung out to the side.

The regulation of the cylinder iris diaphragm is accomplished by means of a lever. Before the condenser is swung back into position the cylinder iris should be opened to its fullest extent. The lower iris diaphragm is for use in connection with the condenser only. It is regulated by means of a small knob. A horizontal rack and pinion arrangement permits oblique illumination, and a vertical rack and pinion permits adjustment of the whole sub-stage. By these means a most perfect control of the illumination of the object is assured. Ground or colored glass discs may be inserted above the iris diaphragm if modification of the light is desired. =$30.--=

_This illuminating apparatus may also be fitted to Stands Ia and Ib._

Swing-out Condenser.

Cylinder Iris Diaphragm.]

=b. Illuminating Apparatus of Stands Ia and Ib= (p. 30, 32, 34).

The following are the parts of this apparatus:

Cylinder diaphragm with 3 stops of different apertures.
Condenser.
Diaphragm carrier with iris diaphragm.
Plane and concave mirror.

To substitute the condenser for the cylinder diaphragm the diaphragm carrier is turned to the side and the cylinder diaphragm is drawn out of the sleeve which holds it in position and into which the condenser readily fits. The diaphragm carrier is then turned back into position and the amount of light regulated by manipulating the knob controlling the size of the iris. The whole sub-stage may be raised or lowered in the optical axis by means of a rack and pinion, and a similar arrangement permits lateral illumination by moving the iris diaphragm in the horizontal plane.

Ground glass and colored plates may be inserted above the iris diaphragm. =$24.--=

=c. Illuminating Apparatus for Stand II and IIa= (p. 36 & 38).

The condenser and iris diaphragm form one piece, giving central but no oblique illumination. The whole apparatus may be raised and lowered in the optical axis by means of a screw. The cylinder diaphragm may be inserted in place of the condenser. A ring below the iris diaphragm permits the insertion of glass discs for the purpose of modifying the light. =$12.--=

=d. Illuminating apparatus for Stand IIb= (p. 40).

The same as for II and IIa fitted in a fixed sleeve; without the side-screw. =$10.--=

=e. Small Illuminating Apparatus.=

The small illuminating apparatus consists of a somewhat smaller condenser with iris diaphragm and can be adjusted to the Stand IV, when it has the cylinder diaphragm. =$8.--=

A cylinder iris diaphragm can be furnished in place of the ordinary cylinder diaphragm of Stand II, IIa and IIb at an additional cost of =$6.--=

Stand III can be had with iris diaphragm fitted in stage, in place of the wheel diaphragm (see page 43) Additional price =$6.--=

=_Complete Microscope Outfits._=

The outfits comprised in the following pages are made up with achromatic objectives, which suffice for all ordinary needs.

We are glad to supply any other combination of eye-pieces and objectives which may be preferred. The price of each outfit may be readily computed by adding together the cost of its various items.

Microscope =stands=, without objectives, will not be sold separately.

=Stand "A".=

Universal Microscope.

In the construction of our new stand "A" we have taken special care to enlarge all the parts proportionately in order to secure strength and stability, at the same time adding to the beauty of the instrument.

The upper pillar of the microscope is shaped in such a way as to form a convenient handle; and to increase the free working space over the stage, thereby allowing the examination of very large specimen and culture plates. A specially constructed mechanical stage larger than No. 98 may be attached, which is adapted for slides up to 2×4 inches (50×100 mm).

The extra large dimensions of all the main parts of this microscope such as the base and stage etc., allow that freedom of movement so desired in a stand for photo-micrography.

Both the body tube and graduated draw tube are very wide and permit the use of low power objectives to cover specimen of large extent; for the same reason the opening in the stage is very wide but can be narrowed down by a stop.

The most important innovation on the microscope is the new fine adjustment device, which is unexcelled both in solidity of construction and accuracy of movement, representing the highest attainment of the designers and mechanics skill.

Sectional cuts of this unique arrangement are shown in illustration (p. 26-27).

All that can be seen on the exterior are two small milled heads mounted below and somewhat back of the two larger knobs controlling the rack and pinion (coarse) adjustment of the microscope. The knob on the right side is provided with a graduated drum _r_, indicating the movement of the fine adjustment.

The two knobs with drum are mounted on an axle _a_, which in its central portion is enlarged and provided with a worm gear. The latter in its turn drives the gear wheel, _d_. A spiral spring pressing against one of the journals into which the axle is mounted prevents any lost motion in the worm gear. Mounted on the same shaft with the gear-wheel _d_, is a heartshaped cam _f_. On this cam rests the steel roller _g_, fitted on the support _k_, which in its turn carries the microscope tube. By its weight and a spiral spring the latter presses on the cam _f_, and effects a direct vertical movement.

The periphery of the heart shaped cam _f_, is exactly symmetrical and mathematically correct. The distance traversed by its curved sides from the lowest to the highest point and vice versa is 3 mm. There are cut 60 teeth in the entire periphery of the gear-wheel _d_; the number corresponding to one side of the heart-shaped cam or 3 mm elevation, are 30 teeth, therefore 1 tooth means a movement of 3/30 mm or 0,1 mm.

This in turn requires one complete revolution of the axle _a_, the drum of which is graduated into 100 parts. The value of each division on the drum is therefore 0,1/100=0,001 mm.

This micrometer fine adjustment is exceedingly accurate and reliable, and besides it has the following advantages;

By virtue of its unique construction the movement is continuous, there is absolutely no limit to the motion of the micrometer screw, which may be turned forward or backward as the work requires.

This movement extends in exact ratio to the revolution of the cam for a distance of 3 mm. As another advantage we may mention, that it is almost impossible to break the coverglass of the specimen with this fine adjustment.

Should the objective come in contact with the coverglass and assuming the knob is turned still further then the tube, which is of aluminium and very light would simply rest on the specimen, without breaking the coverglass, as the latter will easily stand the small pressure of the tube and the fine spiral spring.

No. $

1. New microscope stand "A" inclinable with hinged joint
and clamping lever, fitted with round revolving
centering stage, coarse adjustment by rack and pinion,
new fine adjustment by micrometer-screw (each division
1/1000 mm.) Wide tube, draw tube with millimeter scale.
Large illuminating apparatus with swing-out condenser
and cylinder-iris diaphragm =120.--=
Apochr. 16, 8, 4, oil-imm. 2 mm. N. A. 1,30 =204.--=
Compens. ocular 4, 8, 12, 18 =34.50=
Compens. ocular No. 6 with micrometer and drawing
ocular No. 93 =18.50=
Large mechanical stage No. 99, for object slides
up to 2×4 inches =32.--=
Triple nose-piece =8.--=
------------
Magnif. 70--2250. =417.--=

2. The same stand and illum. apparatus;
Object.: 2, 4, 6, oil-imm. 1/12, N. A. 1,30
Ocul. 0. I. III. IV. V. microm. ocul. II.
Triple nosepiece =210.--=

Stand I.

3. =Large microscope=, inclinable, with hinged joint and
clamping lever and fitted with round revolving centering
stage. Coarse adjustment by rack and pinion, new fine
adjustment by micrometer-screw, the head of which is
graduated each division = 1/1000 mm. Draw-tube with (see
page 25-26) millimetre scale. Large illuminating
apparatus with swing-out condenser and cylinder iris
diaphragm (illustrated on page 21).
Mechanical stage, No. 98.
Triple nose-piece.
Drawing eye-piece, No. 93.
Micrometer eye-piece, No. 84.
Achromatic objectives Nos. 1, 3, 6.
Oil-Immersion 1/12, N. A. 1,30.
Eye-pieces 0, I, III, IV, V.
Magnifications 12--1300 =236.--=

4. =The same= stand and illuminating apparatus.
Triple nose-piece.
Micrometer eye-piece, No. 84.
Drawing eye-piece, No. 93.
Objectives 2, 4, 6, Oil-Immersion 1/12, N. A. 1,30.
Eye-pieces I, III, IV, V.
Magnifications 33-1300 =210.--=

=The stand= and illuminating apparatus without objectives, oculars and nose-piece =112.--=

=Stand Ia.=

4a. =Large Microscope=, of smaller size than Stand I,
fitted with horseshoe foot. The stand is inclinable and
fitted with revolving centering stage, coarse adjustment
by rack and pinion, fine adjustment by micrometer screw
with scale. Draw-tube with millimetre scale. Large
Illuminating Apparatus (Cf. p. 22, b) with rack and
pinion, and iris-diaphragm with oblique movement. The
cylinder-diaphragm and condenser may be readily
substituted for one another.
Triple nose-piece.
Objectives 2, 4, 6, Oil-Immersion 1/12, N. A. 1,30.
Eye-pieces I, III, IV, V.
Magnifications 33-1300 =160.--=

4b. =The same= with Illuminating Apparatus.
Triple nose-piece.
Objectives 3, 6, Oil-Immersion 1/12, N. A. 1,30.
Eye-pieces I, III, IV.
Magnifications 60-1000 =148.--=

4c. =The same= with Illuminating Apparatus.
Triple nose-piece.
Objectives 3, 6, Oil-Immersion 1/10, N. A. 1,30.
Eye-pieces II and IV.
Magnifications 70-730 =136.--=

=Stand= with Illuminating Apparatus, but without
objectives, eye-pieces and nose-piece =76.--=

=The same= with Illuminating Apparatus, Swing-out
Condenser and Cylinder Iris-diaphragm (p. 20, a) =82.--=

Mechanical stage No. 98 can be fitted to this stand;
price =28.--=

=Stand Ia=
with English foot.

4d. =Large Microscope= differing from the foregoing (Ia)
stand only in being provided with an English foot, which
makes the stand somewhat steadier and lighter. The
prices and combinations are otherwise the same.

Dr. P. G. Unna of Hamburg uses this microscope in his
laboratory.

The stage revolves and centres. The illuminating
apparatus is that described on p. 22, b.
Triple nose-piece.
Objectives 2, 4, 6, Oil-Immersion 1/12, N. A. 1,30.
Eye-pieces I, III, IV, V.
Magnifications 33--1300 =160.--=

4e. =The same= with the illuminating apparatus.
Triple nose-piece.
Objectives 3, 6, Oil-Immersion 1/12, N. A. 1,30.
Eye-pieces I, III, IV.
Magnifications 60--1000 =148.--=

4f. =The same= with illuminating apparatus.
Triple nose-piece.
Objectives 3, 6, Oil-Immersion 1/10, N. A. 1,30.
Eye-pieces II, IV.
Magnifications 70--730 =136.--=

=The stand= with illuminating apparatus, but without
objectives, oculars and nose-piece =76.--=

=The stand= with swing-out condenser (p. 20, a) =82.--=

Mechanical stage No. 98 can be fitted to this
stand; price =28.--=

=Stand Ib.=

5. =Large Microscope=, which differs from Ia only in the
stage. The stage is fixed and square. The stand is
inclinable and has a hinged joint and clamping lever.
Draw-tube with millimetre scale. Coarse adjustment by
rack and pinion, fine adjustment by micrometer screw
with graduated head. Illuminating Apparatus, same as Ia
(p. 22, b).
Triple nose-piece.
Objectives 3, 6, Oil-Immersion 1/12, N. A. 1,30.
Eye-pieces I, III, IV.
Magnifications 60--1000 =142.--=

6. =The same= with simplified Illuminating Apparatus (p. 22, c).
Triple nose-piece.
Objectives 3, 6, Oil-Immersion 1/10, N. A. 1,30.
Eye-pieces I, III, IV.
Magnifications 60--730 =120.--=

7. =The same= without Illuminating Apparatus, with Cylinder-diaphragm.
Double nose-piece.
Objectives 3, 7.
Eye-pieces I, III.
Magnifications 60--450 =74.--=

8. =The same= without Illuminating Apparatus and without
nose-piece.
Objectives 3, 7.
Eye-pieces I, III.
Magnifications 60--450 =68.--=

=Stand= without objectives and eye-pieces, without
illuminating apparatus and without nose-piece =46.--=

=Stand= without objectives and eye-pieces, with
illuminating apparatus, without nose-piece =70.--=

=The same= with illuminating apparatus, with swing-out
condenser and cylinder iris-diaphragm (p. 22 a) =76.--=

=Stand II.=

9a. =Medium Size Microscope=, inclinable, with revolving
centering vulcanite stage, coarse adjustment by rack and
pinion, fine adjustment by micrometer-screw. Draw-tube
with millimetre scale. Illuminating apparatus and iris-
diaphragm with lateral screw for raising and lowering.
A ring under the iris diaphragm serves to hold a ground
glass or colored disc. The illuminating apparatus and
cylinder diaphragm are easily interchangeable.
Triple nose-piece.
Objectives 3, 6, Oil-Immersion 1/12, N. A. 1,30.
Eye-pieces I, III, IV.
Magnifications 60--1000 =126.--=

9b. =The same= with Illuminating Apparatus.
Triple nose-piece.
Objectives 3, 6, Oil-Immersion 1/10, N. A. 1,30.
Eye-pieces II, IV.
Magnifications 70--730 =114.--=

9c. =The same= without Illuminating Apparatus.
Triple nose-piece.
Objectives 3, 6, 8.
Eye-pieces I, III.
Magnifications 60--550 =90.--=

9d. =The same= without Illuminating Apparatus.
Double nose-piece.
Objectives 3, 7.
Eye-pieces I, III.
Magnifications 60--450 =72.--=

9e. =The same= without Illuminating Apparatus and nose-piece.
Objectives 3, 7.
Eye-pieces I, III.
Magnifications 60--450 =66.--=

=Stand= with Illuminating Apparatus and Iris-diaphragm,
without objectives, eye-pieces and nose-piece. =54.--=

=The same stand= with Cylinder Diaphragm =44.--=

=Stand= with illuminating apparatus, swing-out condenser
and cylinder iris diaphragm =60.--=

=Cylinder iris diaphragm= (Cf. p. 23) =6.--=

=Stand IIa.=

9. =Medium Size Microscope=, inclinable, coarse adjustment
by rack and pinion, fine adjustment by micrometer-screw.
Draw-tube with millimetre scale. Illuminating apparatus
and iris-diaphragm with lateral screw for raising and
lowering. A ring under the iris diaphragm serves to
hold a ground glass or colored disc. The illuminating
apparatus and cylinder diaphragm are easily interchangeable.
Triple nose-piece.
Objectives 3, 6, Oil-Immersion 1/12, N. A. 1,30.
Eye-pieces I, III, IV.
Magnifications 60--1000 =120.--=

10. =The same= with Illuminating Apparatus.
Triple nose-piece.
Objectives 3, 6, Oil-Immersion 1/10, N. A. 1,30.
Eye-pieces II, IV.
Magnifications 70--730 =108.--=

11. =The same= without Illuminating-Apparatus.
Triple nose-piece.
Objectives 3, 6, 8.
Eye-pieces I, III.
Magnifications 60--550 =84.--=

12. =The same= without Illuminating Apparatus.
Double nose-piece.
Objectives 3, 7.
Eye-pieces I, III.
Magnifications 60--450 =66.--=

13. =The same= without Illuminating Apparatus and nose-piece.
Objectives 3, 7.
Eye-pieces I, III.
Magnifications 60--450 =60.--=

=Stand= with Illuminating Apparatus and Iris-diaphragm,
without objectives, eye-pieces and nose-piece =48.--=

=The same stand= with Cylinder Diaphragm =38.--=

=Cylinder iris-diaphragm= (Cf. p. 23) =6.--=

=Stand IIb.=

14a. =Medium Size Microscope=, stand inclinable to the extent
of 45°, tripod foot, coarse adjustment by rack and
pinion, fine adjustment by micrometer screw. Draw-tube
with millimetre scale. Illuminating Apparatus and
Iris-diaphragm permanently connected and sliding in a
sleeve underneath the stage. The cylinder-diaphragm
is used in the same manner. A ring below the iris-diaphragm
serves to hold a ground glass or colored disc.
Triple nose-piece.
Objectives 3, 6, Oil-Immersion 1/12, N. A. 1,30.
Eye-pieces I, III, IV.
Magnifications 60--1000 =104.--=

14b. =The same= with Illuminating Apparatus.
Triple nose-piece.
Objectives 3, 6, 8.
Eye-pieces II, IV.
Magnifications 70--700 =78.--=

15a. =The same= without Illuminating Apparatus.
Double nose-piece.
Objectives 3, 7.
Eye-pieces I, III.
Magnifications 60--450 =50.--=

15b. =The same= without Illuminating Apparatus and nose-piece.
Objectives 3, 7.
Eye-pieces I, III.
Magnifications 85--450 =44.--=

=Stand= with Illuminating Apparatus and Iris-diaphragm =32.--=

=Stand= with Cylinder or Wheel-diaphragm =22.--=

=Cylinder iris-diaphragm= (p. 23) =6.--=

For the addition to this microscope of a lateral screw
for raising and lowering the illuminating apparatus as
on Stand IIa, an extra charge of $2.-- is made.

=Stand III.=

Stand III is now provided with rack and pinion coarse adjustment instead of sliding tube. In consequence a nose-piece can be used on it to better advantage. It will be found an excellent laboratory stand at low price.

16a. =Medium Size Microscope=, non-inclinable stand,
coarse adjustment by rack and pinion, fine adjustment by
micrometer-screw. The draw-tube has a millimetre scale.
Plane and concave mirror. Wheel-diaphragm.
Triple nose-piece.
Objectives 3, 6, 8.
Eye-pieces I, III.
Magnifications 60--550 =66.--=

16b. =The same= without nose-piece.
Objectives 3, 6, 8.
Eye-pieces I, III.
Magnifications 60--550 =58.--=

17a. =The same=, with double nose-piece.
Objectives 3, 7.
Eye-pieces I, III.
Magnifications 60--450 =48.--=

17b. =The same= without nose-piece.
Objectives 3, 7.
Eye-pieces I, III.
Magnifications 60--450 =42.--=

=Stand= with wheel-diaphragm =20.--=

=This stand= can be supplied with iris diaphragm in
stage (see illustration p. 23) instead of
wheel-diaphragm.

=Stand= with iris diaphragm =26.--=

=Stand IV.=

The dimensions of this stand are now larger than formerly. The price has not been changed.

18. =Small Microscope.= Adjustable by sliding tube and
micrometer-screw. The draw-tube is graduated in
millimeters. Cylinder-diaphragm with sliding sleeve.
Concave and plane mirrors, obliquely adjustable.
Objectives 3, 6, 8.
Eye-pieces I, III.
Magnifications 60--550 =52.--=

19. =The same.=
Objectives 3, 7.
Eye-pieces I, III.
Magnifications 60-450 =36.--=

20. =The same= without Cylinder Diaphragm, with Wheel
Diaphragm.
Objectives 3, 5, 7.
Eye-pieces I, III.
Magnifications 60--450 =44.--=

21. =The same.=
Objectives 1, 3, 7.
Eye-pieces I, III.
Magnifications 18--450 =40.--=

22. =The same.=
Objectives 3, 7.
Eye-pieces I, III.
Magnifications 60--450 =34.--=

=Stand= with cylinder-diaphragm, without objectives
and eye-pieces =14.--=

=Stand= with wheel-diaphragm, without objectives and
eye-pieces =12.--=

=Stand V.=

23. =Small Microscope=. Adjustable by sliding tube and
micrometer-screw. Concave mirror.
Objectives 3, 7.
Eye-pieces I, III.
Magnifications 60--450 =30.--=

24. =The same.=
Objectives 3, 5.
Eye-pieces I, III.
Magnifications 60--250 =28.--=

25. =The same.= Plane mirror.
Objectives 1, 3.
Eye-pieces I, III.
Magnifications 18--80 =24.--=

26. =The same.=
Objectives 3.
Eye-pieces I, IV.
Magnifications 60--105 =18.--=

27. =Stand= without objectives and eye-pieces =8.--=

28. =Auxiliary Laboratory Stand=, for the examination of
trichinae and for searching plate cultures. Very large
stage (3-1/2×4 inch.). Adjustable by means of a carefully
constructed rack and pinion, rendering it possible to
focus objectives of fairly high power.
=Stand=, without eye-pieces, objectives or case =8.--=

29. This stand fitted with objective 3, eye-pieces 0 and
IV. Magnifications 40 to 100, in mahogany case fitted
with lock =18.--=

29a. =The same stand= fitted with eye-piece II and
objective having separable front lens, yielding a
magnification of 40 and 100 diam =18.--=

=Glass compressor= with graduation =--.80=

=Glass compressor= without graduation, per pair =--.40=

=Demonstration microscope.=

30a. Adapted for low and medium power. Square stage
with wheel-diaphragm.

Adjustment by sliding tube; after being adjusted
the tube may be fixed by a ring clamp. Detachable
handle.

With clip to hold a sketch or label, etc. Stand
without objective and eye-piece. =6.--=

30b. =The same= with objective 3 and eye-piece I,
magnifying 60 times =14.--=

30c. =The same= with adjusting screw for focussing high
power objectives, with condenser and iris-diaphragm,
without objectives and eye-pieces =18.--=

30d. =The same= with objectives 3 and 6 and eye-piece I.
Magnifications 60 and 255 =38.--=

=Nebelthau's Sliding Microscope.=

(Cf. Zeitschrift für wissenschaftliche Mikroskopie, XIII, 1896.)

31. The sliding microscope is an instrument by means of
which very large microscope sections, as, for example,
large sections of the brain, can be systematically
examined. It is also of service in looking over plate
cultures of bacteria.

The microscope is carried on a heavy beam supported
by two stout pillars under which the stage
moves. The various movements are accomplished by
motion of the microscope on a lateral track upon
its support and by motion of the stage on a similar
track at right angles to the first. The motion of the
microscope is by means of a screw, that of the stage
by double rack and pinion. The extent of the movements
is indicated in each case by a scale, thus
permitting the systematic examination of the entire
specimen.

The stage consists of a glass plate, measuring
16×20 cm, which is carried in a frame supported on
four columns. The tracks permit a motion of the
microscope of 18 cm and of the stage of 13,5 cm. A
mirror under the stage affords ample illumination.

The microscope tube is so arranged that it can be
easily removed from the stand and a simple lens substituted
for it. The coarse adjustment of the microscope
is by rack and pinion. A screw above the objective
serves for fine adjustment. The price of this sliding
microscope, without objectives or oculars, but with a
lens holder and simple lens magnifying eight diameters
is =80.--=

=Flat glass dish= of the same size as the stage to hold
very large sections for the purpose of examining them
while in clearing fluid =1.25=

32. =Dölken's Stand.= (p. 52) The stand is larger than
Stand No. Ia, but is modified as shown in the cut so as
to permit the examination of unusually large
preparations. It is provided with the illuminating
apparatus b (p. 22) and with all the adjustments
necessary to the use of high powers.

=Stand= and illuminating apparatus, without nose-piece =80.--=

$

33. =Travelling Microscope.= This microscope is ready for
use after spreading the foot, drawing out the tube and
setting the mirror and stage in position. It is provided
with all the adjustments of Stand No. V, consisting of
fine adjustment by micrometer-screw, coarse adjustment
by rack and pinion and illuminating apparatus d (p. 22).
The box is arranged so as to accommodate three
objectives and two oculars. It locks, has a handle, and
measures 25×15×7 cm, the whole apparatus weighing 5
pounds.

Price of this microscope with illuminating apparatus,
but without objectives or oculars =32.--=

=The same=, without illuminating apparatus =24.--=

This instrument (in size like the Ib.) combines all the essential features of a large laboratory microscope with a folding stand. It will be found invaluable on scientific expeditions, for research work etc.

When lifted out of the case, spread the two parts forming the base, which are then held by a spring-catch. After raising the tube, turn the stage around and tighten it by means of a lever. It is supplied with large Abbe condenser and Iris diaphragm adjustable by side screw. Coarse adjustment by rack and pinion, fine adjustment by micrometer-screw. Graduated draw-tube. The stand has joint for inclination.

34. =Stand= with Abbe Condenser and Iris-Diaphragm, double
nose-piece =66.--=

35. =The same=, with objectives 3, 6, Oil-Immersion 1/12",
N. A. 1,30. Eye-pieces I, III. Magnifications 60--800 =128.--=

36. =Horizontal Microscope.= This instrument consists of
a microscope tube placed horizontally on a long
extensible column, supported in turn by a tripod base
provided with levelling screws and a round spirit level.
The extension of the upright supporting column is
accomplished by two sliding motions, the lower,
controlled by a set screw only, being intended for
coarser adjustments, the upper, controlled by rack and
pinion, for finer adjustments. A millimeter scale and a
vernier serve to indicate the degrees of the various
motions, so that vertical motion of the microscope tube
to the extent of 1/10 mm may be accomplished.

The microscope tube carries a spirit level and revolves
upon a horizontal disc. The objective, consisting of two
separable doublets, permits three degrees of
magnification of 5, 9 and 48 cm focal distance
respectively. A rack and pinion adjustment serves as
adjustment of the microscope tube. A micrometer, 1 cm
long and divided into 100, in the diaphragm of the
ocular still further increases the availability of the
instrument for making fine and accurate measurements.

The instrument serves as a useful aid in many physical
and physiological investigations.

Price, including objective, ocular and micrometer =40.--=

=Microscopes for Mineralogical Research.=

We construct two Microscopes for mineralogical investigations. Both are adapted for determining the axes of elasticity and for the differentiation of isotropic and anisotropic bodies. Stand I alone is adapted for determining the optical axes and their angles.

Only such objectives, condensers and oculars are available for mineralogical examinations as have been shown after careful examination in polarized light to be free from polarization.

=Mineralogical Stand I.=

37. This microscope corresponds in its dimensions to
Stand Ia as described on page 31. Coarse adjustment by
rack and pinion, fine adjustment by micrometer-screw,
the milled head of which has 50 divisions, each
representing a motion of the objective of 1/100 mm. The
condenser, iris-diaphragm and polarizer can be raised
and lowered by rack and pinion. A triple condenser
facilitates the observation of the axial lines in the
microscope. It is so arranged as to be easily replaced
by a simple diaphragm-carrier. By means of a collar
attached to the end of the tube the objective is brought
into coincidence with the centre of the revolving stage.
This revolving stage is divided into 360 degrees and
fitted with a vernier and index. Two scales on the
stage, at right angles to each other, permit accurate
location of specimens. The Nicol prism, which serves as
a polarizer, can, after turning the iris-diaphragm
aside, be drawn out from under the latter. The zero
position of the Nicol prism is indicated by a line, as
well as the angles 90, 180, 270°. The analyser is
mounted in metal and is firmly fixed above the eye-
piece. The analyser rotates on a disc graduated to 360
deg. The front of the tube has a movable window which
provides access to the inner tube. In the latter is an
opening for the introduction of a Bertrand lens. This
lens serves the purpose of magnifying the interference
figures produced by the converging rays of polarized
light. This lens and the eye-piece can be raised or
lowered by rack and pinion. In the analyzer is a slide
for the insertion of gypsum and quartz plates at an
angle of 45 degrees.

In many investigations it is advisable to employ an
analyzer introduced laterally into the tube, instead of
the one mentioned above.

The following parts are supplied to complete the outfit:
Triple nose-piece.

Eye-piece 0, with Bertrand's quartered quartz plate.

Eye-piece I with cross-lines, Brezina's Calcspath-plate,
cleft perpendicularly to its axis, made to fit over
eye-piece I, Klein's gypsum and quartz plates for
insertion in the opening over the objective.

Price of the stand with these accessories =160.--=

38. =The same= with eye-piece III, objectives 1, 3, 5, 7.
1/12 Oil-Immersion, magnifications 18--800 =236.--=

The new mechanical stage No. 98 (See page 78) can be
fitted to the stand for the purpose of investigating
large preparations and serial sections.

Price =28.--=

=Mineralogical Stand II.=

39. The base and pillar are in one piece, neatly
japanned black. The coarse adjustment is by rack and
pinion.

The stage is revolving and graduated on the edge into
360 degrees. A pointer indicates its position.

The polarizer has stop at zeropoint and also marks at 90°,
180° and 270°. It is held in a spring-sleeve and the
substage can be raised and lowered by lateral screw, or
may be swung to one side. The condenser is mounted in
separate arm above the polarizer and swings out of the
optical axis by means of a lever, if parallel instead of
convergent rays are desired.

The analyzer fits into an opening of the tube above the
objectives and can be instantly thrown in or out of the
optical axis. There is a slot below the analyzer for the
insertion of quartz and gypsum plates.

By means of a collar with two centering screws attached to
the end of the tube, the objective may be brought into the
optical axis.

Price of this microscope with eye-piece I with cross-lines,
Klein's quartz wedge and gypsum plate, red, I. order
=$56.--=

40. =The same= with eye-piece III. and objectives 3 and 5.

Magnifications 60-250 =74.--=

=Dissecting Microscopes and Hand Lenses.=

41. =Large Dissecting Microscope.=

Stand on heavy horse-shoe base, large stage with glass
plate, adjustment by rack and pinion. The lens-carrier
is movable for examining large plates. Illumination by
movable plane mirror and white glass plate. Metal hand-
rests covered with leather may be attached to the sides
of the stage. They fit inside the mahogany case.

A black metal plate with wheel-diaphragm or a milk-
glass-plate can be inserted below the stage, serving as
dark or white back-ground respectively.

Stand without lenses in mahogany case =16.--=

42. =The same= with three aplanatic lenses after
Steinheil, magnifying 8, 16 and 20 diameters =28.--=

43. =The same= with these lenses and Abbe's drawing
apparatus =40.--=