Chapter I: The Hyperbola (1)

We are free to express the opinion at the outset, that for various reasons the draughtsman is likely to gain very little advantage by the use of mechanical devices for describing mathematical curves by continuous motion. Such instruments are as a rule not only complicated and expensive, but cumbersome and difficult of adjustment. It may be suggested, _per contra_, that these objections do not apply to the familiar combination of two pins and a string, for tracing the "gardener's ellipse." But we question the propriety of classing a string among strictly mechanical devices; it has its uses, to be sure, but in respect to perfect flexibility and inextensibility it cannot be relied on when rigid accuracy is required in drawing any of the conic sections.

Nevertheless, the construction of such apparatus affords a study which to some is fascinating, and even in the abstract is not devoid of utility. In each case a definite object is presented, and usually a choice of methods of attaining it; success requires a thorough knowledge of the properties of the curve in hand, while ingenuity is stimulated, and familiarity with expedients is cultivated, by the effort to select the most available of those properties, and to arrange parts whose motions shall be in accordance with them. Such exercise of the inventive faculties, then, is good training for the mechanician. And it must not be forgotten that a mechanical movement thus devised for one purpose very frequently is either itself applicable to a different one, or proves to be the germ from which are developed new movements which can be made so; the solution of one problem sometimes furnishing a hint or clew of great value in dealing with another.

We proceed, then, to describe a few instruments of this kind, which we believe to be new, in the hope that in the manner just pointed out they may render a greater service than that for which they are directly intended.

The first of these, shown in Fig. 1, is for the purpose of describing the hyperbola. The properties of the curve, upon which the action of the instrument depends, are illustrated in Fig. 2, where MM, NN, are the two branches of an hyperbola; C the center; AB the major axis; F and F' the foci. If now a tangent TT be drawn at any point as P of either branch, and a perpendicular let fall upon it from the nearer focus F be produced to cut at G a line drawn from P to the farther focus F', then this perpendicular will cut the tangent at a point I upon the circumference of a circle described about C upon AB as a diameter, and also the distance F'G will be equal to AB.

In Fig. 1, then, we have a crank CI, whose radius is equal to CB, half the major axis, turning about a fixed center C. Upon the crank-pin I is hung, so as to turn freely, a rigid cross composed of a long slotted piece TT, in which slides a block, and two cylindrical arms at right angles to it and in line with each other, the axis EE passing through I. The arm on the right slides through a socket pivoted at the focus F; the one on the left slides through a similar socket, which is pivoted at G to a third socket longer than the others, which again is pivoted at the focus F'; the distance F'G being equal to AB. Through this long socket slides a rod KP, the end P being formed into an eye, by which this rod is pivoted to the block which slides in the long slot, and thus controls the motion of the block; and the pivot at P is centrally drilled to carry the pencil. It is thus apparent that the center line of the slot TT must in all positions be tangent to the hyperbola PBR, which will be traced by the pencil, whose motions are so restricted as always to satisfy the conditions explained in connection with Fig. 2.

The apparatus as thus represented does not at first sight appear unduly complicated. But in order to render it adjustable, so that hyperbolas of varying eccentricities and on different scales may be drawn with it, several parts not here shown must be added. A frame must be provided, in which to arrange supports for the pivots at F and F', and these supports connected by a right and left handed screw, or equivalent means of altering the distance between the foci; the crank CI and the socket F'G must be of variable length, and these in each case would require to be carefully adjusted. So that, as we stated in the beginning, it is questionable whether a draughtsman of ordinary skill could draw the curve any more readily by the aid of such a piece of mechanism than he could without it; but it may claim a passing notice as a novel device, and the first one, we believe, for describing the hyperbola by a combination of rigid parts.

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EXPERIMENTS WITH FIBERS.

By Dr. THOMAS TAYLOR.

As Microscopist of the United States Department of Agriculture, I am frequently called upon to make investigations as to the character of textile fibers and fabrics, not only for the public generally, but also for several departments of the Government.

Textile fibers are presented both in the raw and as articles of manufacture. In the latter case they may have been dyed, stained, or painted. It is obvious that under these conditions the fibers should be subjected to chemical reaction to bring them as nearly as possible to their normal condition.

Considering how well the structures of the common textile fibers of commerce--cotton, flax, ramie, hemp, jute, Manila hemp, silk, and wool--have been investigated and minutely described by able and exact microscopists, I will in this paper confine myself chiefly to such experiments as I have personally made with textile fibers, treating them with chemical agents while under the objective.

While I am aware that this method is not wholly new, I am satisfied that comparatively little work has been done in this direction, and that a wide field is still open for future research.

As microscopists, we have to fortify ourselves in every way that will sustain, by truthful work, the value of the microscope as a means of research, sometimes conducting our experiments under the most trying circumstances. Fibers may be so treated by experts as to make it difficult to determine how their changed appearance has been effected, and it may happen in this age of experiment and of fraud that important decisions in commercial transactions and in criminal cases may depend on our observations.

DETECTION OF A FRAUD.

A case in point will illustrate this. While Dr. Dyrenforth was chief of the chemical division of the U.S. Patent Office, a person applied for a patent on what he called "cottonized silk," inclosing specimens. He claimed that he had discovered a mode of covering cotton fiber with a solution of silk which could be woven into goods of various kinds; in order to satisfy the public of the reality of his invention, he placed on exhibition, in various localities, specimens of silk-like goods in the form of ribbons in the web and skeins of thread, representing them to be "cottonized silk."

Dr. Dyrenforth was not satisfied that the so-called discovery was an accomplished fact, and he forwarded a few fibers of the material to the division of which I have charge for investigation. I subjected them to my usual tests, and found them to consist of pure silk, and I so reported to Dr. Dyrenforth, who rejected the application for a patent. The microscope was thus usefully employed to protect capitalists from imposition.

METHODS EMPLOYED.

It may be well to state briefly the methods I employed in detecting the real character of the material. The fibers were first viewed under plain transmitted light, secondly, polarized light and selenite plate. Since silk and cotton are polarizing bodies, "cottonized silk," if such could be made as described, would give, in this case, the prismatic colors of both fibers, and the complementary colors would differ greatly because of the great disparity of their respective polarizing and refractive powers.

The fact will be observed that a cotton fiber presents the appearance of a twisted ribbon when viewed by the microscope, while silk, owing to its cylindrical form, cannot twist on itself. It should also be considered that the diameter of "cottonized silk," so called, would be greater than that of a fiber of silk, because the silk solution would have to be applied to an actual thread of cotton, and not to a single cotton fiber, by reason of the shortness of the original hairs of the latter. Were a single fiber of such a combination put under a suitable objective, and a drop of nitric acid brought in contact with the fiber, it would be seen that the acid would destroy the silk and leave the fibers of cotton untouched, the latter being insoluble in cold nitric acid. The action of muriatic acid is similar in this respect. Were a fiber of cotton present and a drop of pure sulphuric acid placed on it, followed quickly by a drop of a transparent solution of the tincture of iodine, a peculiar change in the fiber would take place, provided the right proportion of acid be used. Cotton fiber, and especially flax fiber, under such conditions, forms into disks or beads of a beautiful blue color.

Fig. 1 represents a cotton fiber, and 2, 3, 4, 5 those of flax, as they appear under the acid treatment. Every textile amylaceous fiber is convertible into these forms, more or less, by strong sulphuric acid. The fibers of cotton, flax, and ramie are examples of amylaceous cellulose, that is to say, these fibers are converted into starchy matter by treatment with the last-named acid. Therefore combinations of these fibers in any composition of non-amylaceous fiber (ligneous or woody fiber) will be dissolved, leaving the latter unharmed; the woody fibers remaining will prove suitable objects for examination under the microscope.

COTTON MIXED WITH LINEN.

Again, it might be important to know whether a certain pulp or composition contained flax in combination with cotton. The composition might be of such a well-digested character as to destroy all appearance of normal form, that is to say, the "twisted ribbon" character of cotton, as well as that of the cylindrical and jointed characteristic of flax, might be lost to ordinary view. In this case make a watery solution of the pulp, spread it out thinly on a glass slide 3 inches by one, draw off any superfluous water, then add one or two drops of a strong solution of chromic acid to the preparation, and place over it a glass cover; when viewed by the microscope, any portion of the flax joints present will appear of a dark brown color; a solution of iodine has a similar effect. The brown portions of the joints are nitrogenous in character; cotton fibers are devoid of nitrogen.

EXPERIMENTS WITH FLAX.

A chemist of the Department of Agriculture had once occasion to make experiments with flax fibers, his object being to make them chemically pure; and to this end he treated them with excess of bleaching agents, thus rendering them of a beautiful white, silky appearance, to the naked eye; but when I examined them under the microscope, I found the brown nitrogenous matter of the joints still present, and on using the chromic acid test, they became deeply stained. A chemical solution of flax therefore would prove for some purposes undesirable, owing to the presence of this ligneous matter. A chemical solution of cotton which is destitute of ligneous matter will give a chemically pure solution. Cotton is therefore better adapted than flax for collodion compounds.

WOOL TESTED WITH ACID.

It is known that when wool is treated with the sulphuric acid of commerce or in strong dilute sulphuric acid, the surface scales of the fiber are liberated at one end, and appear, under a low power, as hairs proceeding from the body of the fibers. Wool may remain thus saturated in the acid for several hours, without appearing to undergo any further change, as far as is revealed by the microscope. When treated in mass in a bath of sulphuric acid, strength 60° B., for several minutes, and afterward quickly washed in a weak solution of soda, and finally in pure water and dried, it feels rough to the fingers, owing to the separation of the scales. I have preserved a small quantity of wool thus treated for the last twelve years, my object being to ascertain whether the chemical action to which it was exposed would impair its strength. As far as I can observe, without the aid of the proper tests, it seems to have retained its original tenacity. Wool thus treated seems to possess the property of resisting the ravages of the larvæ of the moth. This specimen, although openly exposed for the period named, suffered no injury from them. Under the microscope, the lubrications appear to have resumed their natural position, and appear finer.

From these experiments it would seem not improbable that a new article of commerce might be produced from wool thus treated, considering that it seems to be moth-proof.

I find in practice that when sable brushes are washed in a weak solution of pure phenic alcohol and afterward in warm water, the moth worm will not eat them. In this way I preserve sable brushes. I mention this chemical fact because it shows that a change of this material is brought about by the phenol as to its edibility, and this may explain why wool treated with sulphuric acid is rendered moth-proof.

I find that when brain matter has been subjected to a solution of weak phenic alcohol, weak alkaline solutions afterward applied fail to separate its nerve-cells on the process of maceration. (This is probably owing to its albuminoids being coagulated by the action of the phenol.) When brain matter is subjected to a weak solution of soda alone, the nerve-cells are easily separated by maceration, and well adapted for microscopic use.

TESTS OF DYED BLACK SILK.

The fibers of dyed black silk may be viewed with interest under the microscope. If a few threads of its warp are placed on a glass slide, and one or two drops of concentrated nitric acid placed in contact with them, the black color changes first to green, then to blue; a life-like motion is observed in all the fibers; they appear marked crosswise like the rings of an earthworm; the surface of each fiber appears loaded with particles of dyestuff; finally the fibers wholly dissolve in the acid. If we now treat a few threads of the weft in the same manner, a similar change of color takes place. When the fibers assume the blue color, a dark line is observed in the center of each, running longitudinally the whole length; this dark line is doubtless the dividing line of the two original normal threads formed directly by the two spinnerets; the dark air line or shadow finally breaks up, and in the course of a few minutes the silk is wholly dissolved. Were ramie, cotton, flax, or hemp present, they would be observed, as all their fibers remain unchanged under this treatment. If wool be present, rapid decomposition will follow, giving off copious fumes of nitrous acid, allowing, however, sufficient time to observe the separation of the scales of the fibers and to demonstrate by observation under the microscope that the fibers are those of wool.

In making these experiments it is not necessary to use a glass disk over the treated fibers. If a disk or cover is pressed on them while undergoing this treatment, the life-like motion of the silk will not be so apparent.

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IMPROVED PYROMETER.

Mr. John Frew, Langloan Iron Works, Coatbridge, has been successful in perfecting a most ingenious pyrometer, an instrument which is capable of continuously indicating every variation of temperature with a remarkable degree of correctness. This instrument, which we here illustrate, has already become known to a number of proprietors and managers of blast furnaces; and on the occasion of the members of the Iron and Steel Institute visiting Coatbridge, in connection with the meeting of that body which was held in Glasgow last autumn, many persons became interested in its construction and in the practical determination of blast temperatures by its readings. Furthermore, Sir William Thomson has expressed himself as being highly delighted with it on account of the manner in which its use illustrates various beautiful scientific principles.

The leading principle on which the construction of this pyrometer has been based is the well-known law of the expansion of gases. Referring to our engraving, it will be seen that at A is a pipe through which air from the cold blast main is admitted into another and larger pipe, B, which reaches nearly to the bottom of a water cistern, C. By means of the inlet and outlet pipes, D and E, the height of the water in the cistern is maintained at a uniform level. In this way there is provided a head of water which retains within the pipe, B, a constant pressure of air, equivalent to the head of water between the open end of that pipe and the overflow at E. Any excess of pressure is prevented by means of the open-ended pipe, which permits the air to escape by the central tube. This latter prevents the agitation caused by the upward rushing air from disturbing the level of the water in the cistern; and in order further to assist this, the central tube is filled loosely in its upper part with lead bullets or other suitable materials supported on a perforated plate. The water level in the cistern is indicated by means of a glass gauge, which is represented at G. To the upper end of the pipe, B, another pipe, H, is attached. This is required for conveying the cold air to the pyrometer proper, for the piece of apparatus above described is simply an arrangement for securing a flow or current of air at constant pressure.

At any point where it is desired to fix a pyrometer, a connection is made with the pipe last spoken of, by means of a small pipe such as is indicated at J, into which is fixed a platinum or other metallic nozzle of small bore, as shown at K. To this same pipe there is attached a solid-drawn copper spiral heater or worm, L, which is fixed into the place or the material the temperature of which it is desired to indicate. Into the outlet of this worm another similar but larger nozzle, M, is fixed. At N is shown a small pipe which is connected with the pipe, J, at any convenient point between the inlet nozzle, K, and the spiral heater, L. The other end of this pipe passes through the India rubber stopper of a small cistern or bottle, O, which, when in use, is about two-thirds filled with a colored liquid. It will be seen that the tube, N, only passes through the stopper, so that it may convey pressure to the surface of the liquid. At P is a glass tube which also passes through the stopper and then to the bottom of the colored liquid; and as its upper end is open, any variation of pressure in the spiral heater is directly transmitted to the indicating column of colored liquid.

The operation of the instrument is as follows: As the cold blast used in the apparatus would be useless for the working of the pyrometer if taken direct from the cold blast main, owing to its irregularity of pressure, the regulator that has been described is employed, and by its means an absolutely steady flow of cold blast air at an unvarying pressure is secured. The diameters of the inlet and outlet nozzles are so nicely adjusted that, so long as both are at the same temperature, the outlet nozzle, which is open to the atmosphere, will pass all the air that the inlet nozzle can deliver without disturbing the pressure in the cistern, O; but if heat be applied to the circulating air through the walls of the spiral heater, the air expands in volume, and is unable to pass through the outlet nozzle in its heated condition as rapidly as it is delivered cold by the inlet nozzle. The consequence is that an increase of pressure takes place in the apparatus between the two nozzles, and it is this pressure that indicates the amount of heat that the air has taken up from the hot blast pipe, in which the spiral heater is fixed. Then, again, as this pressure is directly transmitted to the indicating liquid in the cistern and the vertical tube immersed in it, a rise takes place in the column which is in exact proportion to the expansion of the current of blast passing through the spiral heater.

The method of graduating the indicator scales of the Frew pyrometer is worthy of special notice. When the apparatus is fitted up, and before it is permanently fixed in position, the spiral heater is placed in cold water of known temperature, and the point noted at which the colored liquid stands in the indicator tube. The water is then boiled, and the rise in the liquid in the tube is again noted. Suppose, in the first instance, the cold water temperature to be 62 deg. Fahr., and that, from this point up to 212 deg. Fahr., the liquid to have risen 2¼ in. in the tube; this is equal to 1½ in. per 100 deg. Fahr., and from these data a scale is constructed, the correctness of which is easily verified by transferring the spiral heater into an air bath or oil of high boiling point, and then comparing the readings of the pyrometer scale with those of a mercurial thermometer placed alongside of the spiral heater. By this means it can be clearly demonstrated that, up to the highest point to which it is safe to use a mercurial thermometer, the readings of the pyrometer scale and that of the thermometer are identical.

While this pyrometer is particularly valuable for indicating the temperature of hot blast stoves of every description, there are doubtless many uses that will suggest themselves to persons engaged in various industrial arts and manufactures. The apparatus is neat and substantial in its parts, while it occupies very little space, is not at all liable to derangement, and is entirely automatic in its action. A number of the instruments have been in continuous use at the Langloan Iron Works, with the most satisfactory results, for about eight months. The temperatures they are graduated for vary according to the furnaces with which they are connected and the kind of work to which these are applied.--_Engineering_.

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An exchange gives the following very simple way of avoiding the disagreeable smoke and gas which always pours into the room when a fire is lit in a stove, heater, or fireplace on a damp day: Put in the wood and coal as usual; but before lighting them, ignite a handful of paper or shavings placed on top of the coal. This produces a current of hot air in the chimney, which draws up the smoke and gas at once.

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[FROM PHOTOGRAPHISCHE CORRESPONDENZ.]

ORTHOCHROMATIC PLATES.

By CH SCOLIK.

Since the emulsion process has taken root, no improvement has awakened such a lively, steadily increasing interest as photography of colored objects in their correct tone proportions; a process which makes it possible to reproduce the warmer color-tones, particularly yellow, orange-red, and yellow-green, in their correct light value as they appear to the eye.

In professional circles, as also among the public, the value of this invention cannot possibly be underestimated; an invention with which a new epoch in photography may begin, and by which the handsomest results, particularly in reproductions of oil paintings, can be attained. But in portraiture, as well as in landscape photography, recourse must also be had to orthochromatic plates to obtain effective pictures, particularly as plates can now be produced in which the relative sensitiveness closely resembles that of the ordinary emulsion plate. Although a good deal has been written about this subject, none of these sometimes excellent treatises contains a complete and generally comprehensive formula for the production of color-sensitive plates, and this circumstance causes me to publish my own experiences.

The following coloring matters are particularly recommended in the several publications as preferable:

Eosine yellow and eosine blue shade, iodine cyanin, erythrosine, methyl violet, aniline violet, iodine green, azalein, Hoffmann's violet, acid green, methyl green, rose bengal, pyrosine, chlorophyl, saffrosine, coralline, saffranine, etc.

Particularly important is the correct concentration. The most excellent color matters make the plates oftentimes quite useless by an incorrect proportion of concentration. If this should be too strong, the total sensitiveness will sink (decrease); but when too weak, the color sensitiveness is much reduced.

This fault, particularly, cannot be corrected during washing, but I have mentioned, at the end, how such overcolored emulsion can be made of use before wetting (flowing).

By the addition of some coloring matter to the emulsion, the light sensitiveness of the film toward some individual colored rays is increased, but the sensitiveness for the stronger refractive rays is, as a rule, generally reduced. The result is a loss of the total sensitiveness for white light. Color-sensitive plates are therefore less sensitive to light than ordinary plates of the same origin.

The action of the coloring matter depends also very essentially upon the emulsion. If the emulsion contains iodide of silver, it has a greater sensitiveness for light blue and blue-green light. At all events, the iodide combination must not amount to more than one or two per cent., a small quantity of iodine acting much better upon the total sensitiveness of the plates than can be obtained by pure bromide of silver emulsion.

Methyl violet, rose bengal, and azalein act perceptibly in 1/10000 per cent. upon yellow sensitiveness. Eosine and its varieties, eosine yellow shade, or eosine J, pyrosine J, erythrosine yellowish, may all be noted as very good sensitizers for green, yellow-green, and eventually for yellow. The bluish shades of eosine colors, on the contrary, have an absorption band further in the yellow. This is also the case with the blue shade eosine (eosine B) and the most bluish of all eosines, the bengal rosa. Of both eosines, yellow shade and blue shade, the latter gives a little more intensity.

Although the eosine permits a large limit in the quantity, it will reduce the sensitiveness greatly in larger quantity.

If eosine solution is mixed with bromide of silver emulsion, which is entirely free from nitrate of silver, no eosine silver can form; it acts, therefore, only as an optical sensitizer.

Of the several kinds of cyanin, chlorosulphate, nitrate, and iodide, the latter acts best, as stated by Eder.

Schumann has already said that one drop of cyanin solution, 1 to 2,500 to 6½ c. c. emulsion, already acted as sensitizing in orange; five to ten drops cyanin. 1 to 1,500 to 15 c. c. emulsion, even gave red action.

There are two ways to color the gelatine film with a suitable coloring matter: by mixing the latter directly before filtering into the ready made emulsion, to produce at once colored plates; or to bathe dry emulsion plates for one to five minutes in a solution containing the sensitizing coloring matter. The plates have previously to be soaked for a few minutes, whereupon they are bathed in an aqueous alcoholic solution (with eosine yellow shade and eosine blue shade, in a solution of 1 to 3,000; but with cyanin in a diluted solution of 1 to 5,000). A mixture of 1/10 cyanin and 9/10 eosine yellow shade (of above concentration) acts as a very favorable sensitizer. Lohse recommended bathing of the gelatine plates in a solution of 0.03 eosine and 10 c. c. ammonia in 100 parts of water. He found that very diluted eosine solutions, 1 to 20,000, acted as a yellow sensitizer.

After washing, the plates have to be rinsed and dried--colored plates, as long as they remain moist, being less sensitive than dry ones, and very seldom the reverse.

This bathing of the ready made plates may give good results, but pure and faultless plates are very seldom obtained, wherefore the first mentioned manner (direct addition of color to the emulsion) is to be preferred.

After the experiments made by me, eosine mixtures acted equally in the yellow and blue shade; likewise mixtures of cyanin 1/10 and eosine yellow shade 9/10 were the most favorable. The process with eosine underwent first of all a thorough test, of which the following are the results.

The color, solution I made as follows:

I. 0.5 grm. eosine yellow shade in 750 c.c. alcohol (95 per cent.) is dissolved under good shaking.

II. 0.5 grm. eosine blue shade is also dissolved in 750 c.c. alcohol.

(The emulsion preparation I do not repeat, supposing that everybody is conversant with the same.)

To an emulsion after Monckhoven's method, I add, before filtering, above eosine solutions to 1,000 c.c. emulsion, 15 c.c. each of yellow shade and 15 c.c. of blue shade eosine; mix with a glass stirring-rod, filter, and begin the flowing of the plates. On the contrary, to an emulsion made after Henderson's method, double the quantity of coloring matter can be added before flowing, without reducing the sensitiveness perceptibly.

Cyanin and eosine mixtures I give in the following proportions;

III. 0.5 grm. cyanin (iodo-cyanin) dissolved in 1,000 c.c. alcohol under good shaking.

(All coloring matter solutions have to be filtered.)

To 1,000 c.c. Monckhoven emulsion I give:

25 c.c. eosine solution, yellow shade (I.).

5 c.c. cyanine solution (III.).

With Henderson emulsion I increase to double the quantity.

Further experiments taught me that even if 60 to 80 c.c., and more, of these coloring matter solutions were added, and the emulsion was left to coagulate and then laid in alcohol for several days, after which it was washed well, so that hardly any coloration could be observed, it showed, when making a copy of an oil painting, that the color sensitiveness of the emulsion was not reduced, and that it had rather increased in relative sensitiveness.

Anyhow, I put every colored emulsion for eight days in alcohol, having experienced that hereby, after washing, just a sufficient quantity of the coloring matter will remain as is necessary for the color sensitiveness.

For the correctness of what I have said here, the following experiment made by me will speak:

I mixed with an emulsion a quantity of coloring matter five times increased, flowed a plate with same, which I then exposed, but obtained no picture whatever.

The same emulsion I placed for fourteen days in alcohol, washed it well, and flowed a plate again, which latter had not only the full color sensitiveness, but almost equaled an ordinary emulsion plate in total sensitiveness.

From this can be concluded that--as above said--by placing the emulsion in alcohol, all superfluous coloring matter is removed from the same, and that only the quantity necessary for the color sensitiveness remains therein.

Further, it may be mentioned that it might be of advantage to add to all emulsions eosine besides iodide of silver, because this will give to the emulsion clearness and brilliancy besides color sensitiveness, and produce fine lights.

Finally, I express the hope that these communications may be useful to the practical photographer, and it is my intention to report also about other coloring matters at some future time.--_H.D., in Anthony's Bulletin._

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A NEW PHOTOGRAPHIC APPARATUS.

This apparatus consists of a box containing a camera, A, and a frame, C, containing the desired number of plates, each held in a small frame of black Bristol board. The camera contains a mirror, M, which pivots upon an axis and is maneuvered by the extreme bottom, B. This mirror stops at an angle of 45°, and sends the image coming from the objective to the horizontal plate, D, at the upper part of the camera. The image thus reflected is righted upon this plate.

As the objective is of short focus, every object situated beyond a distance of three yards from the apparatus is in focus. In exceptional cases, where the operator might be nearer the object to be photographed, the focusing would be done by means of the rack of the objective. The latter can also slide up and down, so that the apparatus need not be inclined when buildings or high trees are being photographed. The door, E, performs the _role_ of a shade. When the apparatus has been fixed upon its tripod and properly directed, all the operator has to do is to close the door, P, and raise the mirror, M, by turning the button, B, and then expose the plate. The sensitized plates are introduced into the apparatus through the door, I, and are always brought automatically to the focus of the objective through the pressure of the springs, R. The shutter of the frame, B, opens through a hook, H, with in the pocket, N. After exposure, each plate is lifted by means of the extractor, K, into the pocket, whence it is taken by hand and introduced through a slit, S, behind the springs, R, and the other plates that the frame contains. All these operations are performed in the interior of the pocket, N, through the impermeable, triple fabric of which no light can enter.

An automatic marker shows the number of plates exposed. When the operations are finished, the objective is put back in the interior of the camera, the doors, P and E, are closed, and the pocket is rolled up. The apparatus is thus hermetically closed, and, containing all the accessories, forms one of the most practical of systems for the itinerant photographer.--_La Nature._

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METEORITES.

In our SUPPLEMENT No. 529 we gave an abstract of Prof. Dewars recent series of lectures on the above subject at the Royal Institution. We now present an abstract of the last and concluding lecture.

THE DHURMSALA. METEORITE.

After the conclusion of his last lecture, Prof. Dewar distributed among the younger listeners small pieces of a portion of the Dhurmsala meteorite, which had been broken up for presentation to them by Mr. J.R. Gregory, whose collection of rare minerals was recently to some extent described in these pages. The lecturer stated that Sir F. Abel had given him a large piece of a large meteorite, because he thought that the speaker's piece ought to be bigger than theirs.

Professor Dewar also presented the listeners with a printed detailed account of the fall of the Dhurmsala meteorite, including the report of the occurrence sent to the Punjaub Government, and dated July 28, 1860. The following are the main facts:

"On the afternoon of Saturday, the 14th of July, 1860, between the hours of 2 and 2:30 P.M., the station of Dhurmsala was startled by a terrific bursting noise, which was supposed at first to proceed from a succession of loud blastings or from the explosion of a mine in the upper part of the station; others, imagining it to be an earthquake or very large landslip, rushed from their houses in the firm belief that they must fall upon them. It soon became apparent that this was not the case. The first report, which was far louder in its discharge than any volley of artillery, was quickly followed by another and another, to the number of fourteen or sixteen. Most of the latter reports grew gradually less and less loud. These were probably but the reverberations of the former, not among the hills, but among the clouds, just as is the case with thunder. It was difficult to say which were the reports and which the echoes. There could certainly not have been fewer than four or five actual reports. During the time that the sound lasted the ground trembled and shook convulsively. From the different accounts of three eyewitnesses there appears to have been observed a flame of fire, described as about 2 ft. in depth and 9 ft. in length, darting in an oblique direction above the station after the first explosion had taken place. The stones as they fell buried themselves from 1 ft. to 1½ ft. in the ground, sending up a cloud of dust in all directions. Most providentially, no loss of life or property has occurred. Some coolies, passing by where one fell, ran to the spot to pick up the pieces; before they had held them in their hands half a minute they had to drop them, owing to the intensity of the cold, which benumbed their fingers. This, considering the fact that they were apparently but a moment before in a state of ignition, is very remarkable. Each stone that fell bore unmistakable marks of partial fusion."

Several meteors were seen at Dhurmsala on the evening of the same day.

Dr. C.T. Jackson analyzed a portion of one meteorite weighing 4½ oz.; the piece was 2½ in. long, 1¼ in. wide, and 1 in. in average thickness. In the course of his report he stated: "Its specific gravity is 3.456 at 68 deg. Fahr., barom. 29.9. Its structure is imperfectly granular, but not crystallized, and there are small black specks of the size of a pin's head, and smaller, of malleable meteoric iron, which are readily removed from the crushed stone by the magnet. The color of the mass is ash gray. A portion of the surface is black and is scarified by fusion. Its hardness is not superior to that of olivine or massive chrysolite. Chemical analysis shows that its composition is that of a ferruginous olivine. One gramme of the stone, crushed in an agate mortar, and acted on by a magnet, yielded 0.43 gramme of meteoric iron, which was malleable. After the removal of this a qualitative analysis was made of the residual powder. Another gramme was also taken, without picking out the metallic iron, and was tested for chlorine and for phosphoric acid. The results of the qualitative analysis were that the stone contains silica, magnesia, a little alumina, oxide of iron and nickel, a little tin, an alloy of iron and nickel, phosphoric acid, and a trace of chlorine. These ingredients being determined, the plan for a quantitative analysis was laid out, and was duly executed by the usual and approved methods The following are the results of this analysis, per centum:

Silica, with traces of tin 40.000 Magnesia 26.600 Peroxide of iron 27.700 Metallic iron 3.500 Metallic nickel 0.800 Alumina 0.400 Chlorine 0.049 Phosphoric acid not weighed -- ______ 99.049"

Messrs. Dewar and Ansdell analyzed the gases in the meteorite, of which it contained three times its volume; the gases were in the following proportions to each other:

Carbonic acid 61.29 Carbonic oxide 7.52 Hydrogen 30.96 Nitrogen 0.23 ______ 100.00

* * * * *

TELESCOPIC SEARCH FOR THE TRANS-NEPTUNIAN PLANET.

[Footnote: By David P. Todd, M.A., from the _Proceedings_ of the American Academy of Arts and Science.]

In the twentieth volume of the _American Journal of Science_, at page 225, I gave a preliminary account of my search, theoretic and practical, for the trans-Neptunian planet. I say _the_ trans-Neptunian planet, because I regard the evidence of its existence as well-founded, and further because, since the time when I was engaged upon this search, nothing has in the least weakened my entire conviction as to its existence in about that part of the sky assigned; while, as is well known, the independent researches in cometary perturbations by Prof. Forbes conducted him to a result identical with my own--a coincidence not to be lightly set aside as pure accident.

That five years have elapsed since this coincidence was remarked, and the planet is still unfound, is not sufficient assurance to me that its existence is merely fanciful. In so far as I am informed, this spot of the sky has received very little scrutiny with telescopes competent to such a search; and most observers finding nothing would, I suspect, prefer not to announce their ineffective search.

The time has now come when this search can be profitably undertaken by any observer having the rare combination of time, enthusiasm, and the necessary appliances. Strongly marked developments in astronomical photography have been effected since this optical search was conducted; and the capacity of the modern dry-plate for the registry of the light of very faint stars makes the application of this method the shortest and surest way of detecting any such object. Nor is this purely an opinion of my own. But the required apparatus would be costly; and the instrument, together with the services of an astronomer and a photographer, would, for the time being, be necessarily devoted exclusively to the work. While, however, the photographic search might have to be ended with a negative result, in so far as the trans-Neptunian planet is concerned, there would still remain the series of photographic maps of the region explored, and these would be of incalculable service in the astronomy of the future.

In the latter part of the paper alluded to above, I stated the speculative basis upon which I restricted the stellar region to be examined; also the fact that between November of 1877 and March of 1878 I was engaged in a telescopic scrutiny of this region, employing the twenty-six inch refractor of the Naval Observatory. For the purposes contemplated I had no hesitation in adopting the method of search whereby I expected to detect the planet by the contrast of its disk and light with the appearance of an average star of about the thirteenth magnitude. A power of 600 diameters was often employed, but the field of view of this eye-piece was so restricted that a power of 400 diameters had to be used most of the time. I say, too, that, "after the first few nights, I was surprised at the readiness with which my eye detected any variation from the average appearance of a star of a given faint magnitude; as a consequence whereof my observing book contains a large stock of memoranda of suspected objects. My general plan with these was to observe with a sufficient degree of accuracy the position of all suspected objects. On the succeeding night of observation they were re-observed; and, at an interval of several weeks thereafter, the observation was again verified." Subjoined to the original observations are printed these verifications in heavy-faced type.

In conducting the search, the plans were several times varied in slight detail, generally because experience with the work enabled me to make improvements in method. Usually, I prepared every few days a new zone chart of the region over which I was about to search; and these charts while containing memoranda of all the instrumental data which could be prepared beforehand, were likewise so adjusted with reference to the opposition-time of the planet as to avoid, if possible, its stationary point. The same thing, too, was kept in mind in selecting the times of subsequent observation. Notwithstanding this precaution, however, it would be well if some observer who has a large telescope should now re-examine the positions of these objects.

Researches in faint nebulæ and nebulous stars appearing likely to constitute a separate and interesting branch of the astronomy of the future, it has seemed to me that the astronomers engaged in this work may like to make a careful examination of some of the stars entered in my observing book under the category of "suspected objects." The method I adopted of insuring re-observation of these objects was by the determination, not of their absolute, but only of their relative, positions, through the agency of the larger "finder" of the great telescope. This has an aperture of five inches, a power of thirty diameters, and a field of view of seventy-eight minutes of arc. Two diagrams were usually drawn in the book for each of these objects, the one showing the relation of adjacent objects in the great telescope, and the other the configuration of the more conspicuous objects in the field of view of the finder. Adjacent to these "finder" diagrams are the settings--to the nearest minute of arc in declination, and of time in right ascension--as read from the large finding-circles, divided in black and white. The field of view of the finder is crossed by two pairs of hairlines, making a square of about twelve minutes on a side by their intersection at the center. The diagrams in all cases represent the objects as seen with an inverting eye-piece. As the adjustment of the finder was occasionally verified, as well as the readings of the large circles, there should be no trouble in identifying any of these objects, notwithstanding the fact that no estimates of absolute magnitude were recorded. The relative magnitudes, while intended to be only approximate, are still shown with sufficient accuracy for the purpose of the research, and the diagrams are, in general, faithful tracings from the original memoranda.

[Mr. Todd transcribes the observing book entire.]

* * * * *

[AMERICAN ANNALS OF THE DEAF AND DUMB.]

NOTES ON MANUAL SPELLING.

The inestimable value of speech-reading and the practicability of its acquisition under favorable conditions is a matter of common experience and observation but justice to the deaf requires a recognition of the fact that speech-reading has its limitations. Certain English words, chiefly short ones, are practically alike to the speech-reader and the context may fail sometimes to give a clew. It is necessary, at times, in communicating with even expert speech-readers, to have recourse to writing or oral spelling to convey the names of persons, places, technical terms, etc., not in common use. Moreover, it is convenient to have accurate and rapid means of conversation under unfavorable conditions as to light and distance, or when from any cause the deaf person's voice cannot be heard.

Writing is slow, inconvenient, and often impossible. Writing upon the palm of the hand was proposed by the Abbe Deschamps in 1778, as utilizing the sense of touch, and was used in darkness by him as a substitute for speech, but it is neither accurate nor rapid. Writing in the air[1] with the finger is also slow and uncertain, while the action is unpleasantly conspicuous.

[Footnote 1: The brilliant but wily Sicard, whose "show" pupils were accustomed to honoring drafts at sight in appropriate responses to all sorts of questions, acting upon the motto, _Mundus vult decipi, ergo decipiatur_, schooled certain pupils in deciphering writing in the air, and was thus prepared, in emergencies at his public exhibitions, to convey intimations of the answers, while supposed to be using "signs" in putting questions.]

Finger-spelling would appear to be a far more convenient, easy, rapid, and accurate adjunct to speech or substitute for it than writing.

It is a common error to consider the ordinary manual alphabets as deaf-mute alphabets and finger-spelling as the sign-language of the deaf. Finger-spelling is to the deaf a borrowed art. It is used by many of the educated deaf and their friends as a substitute for the sign-language, and it enables them also to supply the deficiencies of the sign-language by incorporating words from written language. Scagliotti, of Turin, devised a system of initial signs[2] which begin with letters of the manual alphabet, and Dr. Isaac Lewis Peet, of New York, has made a similar application of manual letters to signs to suggest words of our written language to the initiated deaf. But it should not be forgotten that practice in finger-spelling is practice in our language.

[Footnote 2: _Quatrieme Circulaire_, Paris, 1836, p. 16. Carton's _Memoire_, 1845, p. 73.]

The origin of finger-spelling is not known. Barrois, a distinguished orientalist, in his _Dactylologie et Langage primitif_[3], ingeniously traces evidences of finger-spelling, from the Assyrian antiquities down to the fifteenth century upon monuments of art.

[Footnote 3: Barrois: _Dactylologie et langage primitif_, Paris, 1850, Firmin Didot freres.]

The ancient Egyptians, Greeks, and Romans were familiar with manual arithmetic and finger-numeration, as quaint John Bulwer shows by numerous citations in his _Chironomia_ (1644). The earliest finger-alphabets extant appear to have been based upon finger-signs for numbers, as, for instance, that given by the Venerable Bede (672-735) in his _De Loguela per Gestum Digitorum sive Indigitatione_, figured in the Ratisbon edition of 1532.[4] Monks and others who had special reason to prize secret and silent modes of communication, beyond doubt invented and used many forms of finger alphabets as well as systems of manual signs.[5] The oldest plates in the library of the National Deaf Mute College are found in the _Thesaurus Artificiosae Memoriae_ of frater Cosmas P. Rossellius of Florence, printed in 1579, which gives three forms of one-hand alphabets. Bonet's work[6] of 1620 gives one form of the one hand Spanish manual alphabet, which contains forms identical with certain letters in the alphabets of 1579. This was introduced into France by Pereire and taught to the Abbe de l'Epee by Saboureux de Fontenay, the gifted pupil of Pereire. The good Abbe however continued to use a French[7] two-hand alphabet which, he had learned when a child and which he said all school-children knew. He mentions also a Spanish alphabet in part requiring both hands, and remarks that different nations have different manual alphabets. The Abbe Deschamps, a rival of De l'Epee, made use of a finger alphabet in teaching the deaf to speak, which was not adapted to rapid use. John Bulwer, in his _Chirologia, or the Naturall Language of the Hand_, printed in 1644, figures five manual alphabets for secret communication.

[Footnote 4: The library of the New York Institution contains a copy of this very rare edition, bearing the title _Abacus atque velustissima Latinorum per digitos manusque numerandi (quinetiam loquendi) consuetudo_, etc., Ratisbonae, 1532.]

[Footnote 5: For an exhaustive account of the gesture speech in Anglo-Saxon monasteries and of the Cistercian monks, who were under rigid vows of silence, see F. Kluge: _Zur Geschichte der Zeichensprache.--Angelsachsische indicia Monaslerialia,_ in _International Zeitschrift fur Allgemeine Sprachwissenschaft,_ II. Band, I. Halfte. Leipzig, 1885.]

[Footnote 6: _Reduccion de lasletras y arte para ensenar a hablar los mudos_, 1620. The writer is under obligations to Sr. Santos M. Robledo, of the Ministry of Public Works and Education, for advance sheets of the reprint in beautiful facsimile of this rare work ordered by the Spanish Government in 1881.]

[Footnote 7: The Abbe de l'Epee did not master the Spanish alphabet, and, attaching but little importance to manual spelling, he was unsparing in his criticism of _Messieurs the dactylologists_, but by "the irony of fate" this alphabet occupies a face of the pedestal of one statue to his memory, and in another statue the good Abbe is represented either as receiving this alphabet from the skies or as devoutly using it.]

The first alphabet which appears to have been devised expressly for use in teaching the deaf is that of George Dalgarno, of Aberdeen (1626-1687), given in his remarkable philosophical treatise, _Didascalocophus, or the Deaf and Dumb Man's Tutor_, Oxford, 1680. A facsimile of this alphabet is given in the _Annals_, vol. ix., page 19. Words are spelled by touching with your finger the positions indicated, either upon your hand or upon the hand of your interlocutor. An alphabet of the same character, however, was not unknown at an earlier date. For Bulwer, in 1648, says: "A pregnant example of the officious nature of the Touch in supplying the defect or temporall incapacity of the other senses we have in one Master _Babington_ of _Burntwood_ in the County of _Essex_, an ingenious gentleman, who through some sicknesse becoming _deaf_, doth notwithstanding feele words, and as if he had an eye in his finger, sees signes in the darke; whose Wife discourseth very perfectly with him by a strange way of Arthrologie or Alphabet contrived on the joynts of his Fingers; who taking him by the hand in the night, can so discourse with him very exactly; for he feeling the joynts which she toucheth for letters, by them collected into words, very readily conceives what shee would suggest unto him. By which examples [referring to this case and to that of an abbot who became _deaf, dumb_, and _blind_, who understood writing traced upon his naked arm] you may see how ready upon any invitation of Art, the _Tact_ is, to supply the defect, and to officiate for any or all of the other senses, as being the most faithfull sense to man, being both the _Founder_, and _Vicar generall_ to all the rest."[8]

[Footnote 8: _Philocophus_: or, THE DEAFE and Dumbe Mans Friend. By I.B. [John Bulwer] sirnamed the _Chorosopher_. London, 1648. Pp. 106,107.]