Chapter VI: Conclusion

The general conclusion to which these experiments bring us is that, undoubtedly, if it could certainly be relied upon, the electric car would be the preferable form of tramway motor in towns, because it is simply a self-contained ordinary tram-car, and in a town the service requires a number of separate cars, occupying as small a space each as is compatible with accommodating the passengers, and which follow each other at rapid intervals.

But the practicability and the economy of a system of electric tram-cars has yet to be proved; for the experiments at Antwerp, while they show the perfection of the electric car as a means of conveyance, have not yet finally determined all the questions which arise in the consideration of the subject. For instance, with regard to economy, the engine employed to generate the electricity was not in thoroughly good order, and from its being used to do other work than charging the accumulators of the tram-car, the consumption of fuel had to be to some extent estimated. In the next place, the durability of the accumulators is still to be ascertained; upon this much of the economy would depend. And in addition to this question, there is also that of the durability of parts of the machinery if exposed to dust and mud.

After the electric car, there is no question but that at the Antwerp Exhibition the most taking of the tramway motors was the Rowan, which was very economical in fuel, quite free from the appearance of steam, and very convenient and manageable.

The economy of the Rowan motor arises in a large degree from the extent of its condensing power, by means of which a considerable supply of warm water is constantly supplied for use in the boiler, and consequently the quantity of water which has to be carried is lessened, and the fuel is economized.

Independently, however, of its convenience as a motor for tramways in towns, the Rowan machine has been adapted on the Continent to the conveyance of goods as well as passenger traffic on light branch railways, and fitted to pass over curves of 50 feet radius, and up gradients of 1:10.

In England, with our depressed trade and agriculture, there is a great want in many parts of the country of a cheap means of conveyance from the railway stations into the surrounding districts; such a means of conveyance might be afforded by light railways along or near the road-side, the cost of which would be comparatively small, provided that the expensive methods of construction, of signaling, and of working which have been required for main lines, and which are perfectly unnecessary for such light railways, were dispensed with.

It is certain that this question will acquire prominence as soon as a system of local government has been adopted, in which the wants of the several communities have full opportunity of asserting themselves, and in which each local authority shall have power to decide on those measures which are essential to the development of the resources of its own district, without interference from a centralized bureaucracy.

* * * * *

ON THE THEORY OF THE ELECTRO-MAGNETIC TELEPHONE TRANSMITTER.

By E. MERCADIER.

[Footnote: Note presented to the Academy of Sciences, Oct. 19, 1885.]

The first point to be studied in this theory is the _role_ performed by the iron or steel diaphragm of the telephone, both as regards the nature of the movements that it effects through elasticity and the conversion of mechanical into magnetic energy as a result of its motions.

I. When we produce simple or complex vibratory motions in the air in front of the diaphragm, like those that result from articulate speech, either the fundamental and harmonic sounds of the diaphragm are not produced, or else they play but a secondary _role_.

(1.) In fact, diaphragms are never set in vibration, as is supposed, when we desire to determine the series of harmonics and nodal lines, since we do not leave them to themselves until they have been set in motion, and we do not allow a free play to the action of elastic forces; in a word, the vibrations that they are capable of effecting are constantly _forced_ ones.

(2.) When a disk is set into a groove, and its edges are fixed, theory indicates that the first harmonics of the free disk should only rise a little. Let us take steel disks 4 inches in diameter and but 0.08 inch in thickness, and of which the fundamental sound in a free state is about _ut_{5}_, and which the setting only further increases. It is impossible to see how this fundamental and the harmonics can be set in play when a continuous series of sounds or accords below _ut_{5}_, are produced before the disk; and yet these sounds are produced perfectly (with feeble intensity, it is true, in an ordinary telephone) with their pitch and quality. They produce, then, in the transmitting diaphragm other motions than those of the fundamental sound and of its peculiar harmonics.

(3.) It is true that in practice the edges of the telephone diaphragm are in nowise fixed, but merely set into a groove, or rather clamped between wooden or metallic rings, whose mass is comparable to their own; and they are, therefore, as regards elasticity, in an ill ascertained state. Yet a diaphragm of the usual diameter (from 2 to 4 inches), and very thin (from 0.001 to 0.02 inch), clamped in this way by its edges, is capable of vibrating when a continuous series of sounds are produced near it, by means, for example, of a series of organ pipes. But the series of sounds that it clearly re-enforces, in exhibiting a kind of complex nodal lines, is plainly _discontinuous_; and how, therefore, would the existence of such series suffice to explain the production of a _continuous_ scale of isolated or superposed sounds, the chief property of the telephone?

(4.) The interposition of a plate of any substance whatever between the diaphragm and the source of the vibratory motions in nowise alters the telephonic qualities of the diaphragm, and consequently the _nature_ of the motions that it effects--a fact that would be very astonishing if the motions were those that corresponded to the peculiar sounds of the diaphragm. This fact is already known, and I have verified it with mica, glass, zinc, copper, cork, wood, paper, cotton, a feather, soft wax, sand, and water, even in taking thicknesses of from 5 to 8 inches of these substances.

(5.) We can put a diaphragm manifestly out of condition to effect its peculiar scale of harmonics by placing small, unequal, and irregularly distributed bodies upon its surface, by cutting it out in the form of a wheel, and by punching a sufficient number of holes in it to reduce it half in bulk. None of these modifications removes its telephonic qualities.

(6.) We can go still further, and employ diaphragms of scarcely any stiffness and elasticity without altering their essential telephonic properties, the reproduction of a continuous series of sounds, accords, and timbres. Such is the case with a sheet iron diaphragm. It is very difficult, then, to imagine a fundamental sound and its harmonics.

The conclusion from all this appears to me to be that the mechanism by virtue of which telephone diaphragms perform their motions is at least analogous to, if not identical with, that through which solid bodies of any form whatever (a wall, for example) transmit to all of their surfaces all the simple or complex successive or simultaneous vibratory motions, of periods varying in a continuous or discontinuous manner, that are produced in the air in contact with the other surface. In a word, we have here a phenomenon of _resonance_. In diaphragms of sufficient thickness this kind of motion would exist alone. In thin diaphragms the motions that correspond to their special sounds might become superposed upon the preceding, and this would be prejudicial rather than useful, since, in such a case, if there resulted a re-enforcement of the effects produced, it would be at the expense of the reproduction of the timbre, the harmonics of the diaphragm being capable of coinciding only through the merest accident with those of the sounds that were setting in play the fundamental sound of the diaphragm. This is what experiment clearly demonstrates.

II. Let us now pass to the _magnetic role_ of the telephone diaphragm. Such _role_ can be clearly enough defined by the following facts:

(1.) The presence of the magnetic field of the telephone in nowise changes the preceding conclusions.

(2.) Upon farther and farther diminishing the stiffness and elasticity of the diaphragm, I have succeeded in suppressing it entirely. In fact, it is only necessary to substitute for it, in any telephone whatever, a few grains of iron filings, thrown upon the pole of the magnet, covered with a bit of paper or cardboard, in order to render it possible to reproduce all sounds, and articulate speech with its characteristic quality, although, it is true, with very feeble intensity.

(3.) In order to increase the intensity of the effect produced, it suffices to substitute for the iron diaphragm a thin disk of any sort of slightly flexible substance, metallic or otherwise, cardboard, for example, and through the aperture of the usual cover of the instrument to scatter over it from 1½ to 3 grains of iron filings. In this way we obtain an iron filings telephone. By properly increasing the intensity of the magnetic field, I have been able to form telephones of this kind that produced in an ordinary receiver as intense effects as those given by the usual transmitters with stiff disks, and which, too, were reversible. But for a field of given intensity, there is a weight of iron filings that produces a maximum of effect.

We thus see that the advantage of the iron diaphragm over filings is truly reduced to the presentation of a much larger number of magnetic molecules to the action of the field and to external actions, within the same volume. It increases the _intensity_ of the telephonic effects, although for _the production_ of the latter with all their variety, fineness, and perfection it is nowise indispensable. It suffices, after a manner, to materialize the lines of force with iron filings, and to act mechanically upon them, and consequently upon the field itself.

* * * * *

ON THE THEORY OF THE RECEIVER OF THE ELECTRO-MAGNETIC TELEPHONE.

By E. MERCADIER.

[Footnote: Note presented to the Academy of Sciences, November 16, 1885.]

On a former occasion I described some experiments that had led me to a theory of the telephone transmitter; a few words will suffice to expose that of the receiver.

Such theory gave rise during the first years succeeding the invention of the telephone to a considerable number of investigations, the principal results of which may be summed up in the two following points:

1. All the parts of a telephone receiver--core, helix, disk, handle, etc.--vibrate simultaneously (Boudet, Laborde, Breguet, Ader, Du Moncel, and others). But there is no doubt that by far the most energetic effects are those of the disk. It has been possible to put the vibrations of the core and helix beyond a doubt only by employing very energetic transmitter currents, or very simplified and special arrangements of the receiver (Ader, Du Moncel, and others).

2. In telephone receivers we may employ disks or diaphragms of any thickness up to six inches (Bell, Breguet, and others).

From the first point it had already resulted that the diaphragm was no more indispensable in the receiver than it was in the transmitter, as I have already shown (_Comptes Rendus_, t. ci., p. 944); and, from the second point, that there were other effects in a receiver than those that could result from the transverse vibrations corresponding to the fundamental sound and to the harmonics of the diaphragm.

So Du Moncel, basing a theory upon these two categories of facts, asserted that the effects of the telephone receiver were principally due to the molecular vibrations of the core of the electro-magnet (analogous to those that had been studied by Page, De la Rive, Wetheim, Reis, and others), super-excited and re-enforced by the iron diaphragm operating as an armature.

This theory has certainly truth for a basis; but it is incomplete, in that the molecular vibrations of the core are but a very feeble accessory phenomenon, and not a prominent one. At all events, I believe that we can, in a few words, and very simply, present the theory of the telephone receiver by going back to the facts that served me as a basis for the theory of the transmitter, and that result from studies made with telephones of ordinary forms.

In fact, it is enough to remark that the iron filings telephone transmitter described in a preceding article (_1. c_.) is reversible and capable of serving as a receiver--not a very intense one, it is true, but here it is a question of the _nature_ of the phenomena, and not of their intensity. It at once results that in receivers, as in transmitters, the rigidity of the iron diaphragm is in nowise indispensable for telephonic effects, such as the production of continuous series of successive or simultaneous sounds and of articulate speech.

The diaphragm serves but to increase the intensity of these effects, as in the transmitter, by concentrating the lines of force of the field, and by presenting a greater surface to the air--the necessary vehicle of sound. When it is thick, the internal motions that it takes on in consequence of variations in the field, and which are transmitted to the surrounding air and the ear, are solely those of resonance. When it is very thin, the peculiar motions resulting from its geometric form and its structure may become superposed upon the preceding, because it may then happen that the corresponding sounds remain within the limits of the pitch wherein the human voice usually moves (from ut_{2} to ut_{5}); but then, also, as the harmonics of the voice in nowise coincide with the proper sounds of the diaphragm, the intensity of the effects is obtained at the expense of a good reproduction of the timbre. This is certainly one of the causes of the nasal timbre of most thin-diaphragmed telephones. By diminishing their thickness, we lose in quality what we gain in intensity.

But even in this latter respect there is a maximum for receivers, as I have already pointed out that there is for iron filings transmitters. For a magnetic field of given intensity, there is, all things equal, a diaphragm thickness that gives a maximum telephonic result. Such result, which is analogous to those that occur in other electro-magnetic phenomena, may explain the want of success of many tentatives made somewhat at haphazard, with a view to increasing the intensity of telephonic effects.

* * * * *

DECOMPOSITION AND FERMENTATION OF MILK.

Dr. F. Hueppe, who has paid great attention to this subject, describes five distinct organisms which he finds to be invariable accompaniments of lactic fermentation. One of these he isolated on nutrient gelatine in the form of white, shining, flat, minute beads. This organism has the power of transforming milk sugar and other saccharoses into lactic acid, with evolution of carbonic acid gas. It is rarely found in the saliva or mucilage of the teeth. In these are two micrococci, both of which cause the production of lactic acid, but which manifest differences in their development under cultivation. There are also two pigment forming bacteria, _Micrococcus prodigiosus,_ which produces intensely red spots, and the yellow micrococcus of osteomyelitis. These five bacteria are so different and so constant in their properties that they must, in Dr. Hueppe's opinion, be regarded as distinct species. In addition to them there is in milk an organism resembling _Mycoderma aceti_, which transforms milk sugar into gluconic acid.

* * * * *

THE NEW "BURGTHEATER" IN VIENNA.

At last the new "Burgtheater" in Vienna is completed. We say "at last," for work was begun on this new theater more than ten years ago. One after another, monumental architectural works have been erected, which are no less grand and beautiful than this. They were finished long ago, and given over to their respective uses--the Parliament buildings, the "Rathhaus," the University; but Baron Hasenauer, who had charge of the construction of this building, as well as of many others, could not bring himself to the quicker _tempo_ of Messrs Hansen, Schmid, and Ferstel. The citizens of Vienna were naturally impatient to see their beautiful "Ringstrasse" completed, and only the Hasenauer buildings were needed to make it perfect.

The building was built according to the plans of Semper and Hasenauer; for, as in the other great buildings erected by Hasenauer, the new palace and the museums, Semper's plans served as a foundation. All the modern improvements in the architecture of theaters have been embodied in the new theater, for the terrible catastrophe at the Ringtheater taught a lesson which has not been forgotten, and the greatest care has been taken to guard against fire.

The new "Burgtheater" stands directly opposite the imposing "Rathhaus" (senate-house), and is separated from the same by a charming park; to the right stands the University, and to the left the Houses of Parliament. In order to be worthy of such company, and not be overshadowed by these buildings, it was necessary that the theater should be very grand. The most important requirements have been perfectly fulfilled; beauty, elegance, appropriateness, and security against fire, nothing has been neglected.

The principal part of the building stands out strongly, and is flanked on either side by a pavilion-like wing. The audience room will accommodate about two thousand people.

The public and the actors alike rejoice in the new Burgtheater, for which they have waited so long.

* * * * *

THE NEW GERMAN BOOKDEALERS' EXCHANGE IN LEIPZIG.

It seems strange that book-printing and the book trade in general should have developed so slowly in the busy city of Leipzig, where a university was established as early as the beginning of the fifteenth century. The first honorable mention of the printing of Leipzig was made during the first decade of the sixteenth century, but it was not until the end of the seventeenth century that the printing and publishing of books received a notable impulse, which was given it by Messrs. J.F. Gleditsch and Thomas Fritsche and Profs. Carpzov and Mericke, who published many works of great typographical beauty.

From 1682 to 1700 ninety-one papers and periodicals appeared in Leipzig, of which the _Acta eruditorum_ was the oldest, being the first German scientific paper. At this time there were seventeen printing establishments in Leipzig, and the seventy presses in use printed, on an average, 2,000 bales of paper yearly.

One of the leading bookdealers, Philipp Emanuel Reich, won the approbation of his fellow citizens by establishing the first Bookdealers' Association at the time of the Easter Fair in Leipzig, in 1764, and it was through his efforts that the Book Exchange or Fair was founded, which has placed Leipzig at the head of the book trade; but several years passed before this private undertaking become a public association. About 1834 a building was erected specially for a book exchange or bourse, but this building was soon outgrown, and it was decided to build a new one which should be adequate to the requirements of the institution.

A competition for designs for the new building was opened, and five designs were presented, from which the plan of Messrs. Kayser and Von. Grossheim, of Berlin, was selected. This design, which is shown in the accompanying cut, taken from the _Illustrirte Zeitung,_ presents a picturesque grouping of the different parts of the building, the main building being on one street and the adjoining building on another street. The roof, which forms a beautiful sky-line, is ornamented with dormer-windows and little towers, there being a large tower on the main building.

To the left of the principal hall in the main building, which has three large ornamental windows, there is a little hall, the central office, and committee rooms, while the restaurant and the assembly rooms are on the right. In the smaller building, through which there is a central corridor, are the order rooms, assorting rooms, editorial sanctum of the _Borsenblat_ (Bourse journal), and the post office, with telegraph offices.

A low building runs almost the entire length of the main building, to which it is joined at the right and left by side wings, thus inclosing an open court. In this low building the exhibition rooms are arranged, and in the middle is a vestibule through which these exhibition rooms, the wardrobes, and the great hall can be reached. Over the vestibule is a cupola.

The arrangements for lighting, heating, and ventilation are excellent. Steam heat is used, and the large hall is ventilated by the pulsation system.

The building, which is of red brick and sandstone, is worthy of holding a place among the numerous beautiful buildings which have been erected in Leipzig during the last few years. The cost of the building was limited to 700,000 M., or about $160,000.

* * * * *

A correspondent has transmitted to the editor of _L'Union Pharmaceutique_ the prospectus of an oyster dealer who, besides dealing in the ordinary bivalves, advertises specialties in medicinal oysters, such as "huitres ferrugineuses" and "huitres au goudron." The "huitres ferrugineuses" are recommended to anæmic persons, and the "huitres au goudron" are said to replace with advantage all other means of administering tar, while of both it is alleged that analyses made by "distinguished _savants_" leave no doubt as to their valuable qualities.

* * * * *

ALIZARINE DYES.

Notwithstanding the unprecedented progress of the coal-tar dyestuff industry during the past few decades, the time-honored indigo, logwood, fustic, etc., have been only partly displaced by the coal-tar products in wool dyeing. The cause is that, though the dyer handled many aniline dyestuffs which dyed as fast against light as logwood or fustic, the dye proved unsatisfactory for fulling goods, because it bled in the treatment with soap and soda, and often more or less changed its tone. We intend to render a service to our readers by calling their special attention to some products of the coal-tar industry which are free from these defects of aniline dyestuffs, and for which it is claimed that they far surpass logwood, fustic, cudbear, etc., as to fastness against light, and excellently stand fulling. We allude to the alizarine dyestuffs, which have long since been introduced and are largely employed in cotton dyeing and printing.

Alizarine, which has been extensively discussed in various articles in our journal, is the coloring matter contained in the madder root. In 1869, two German chemists, Graebe and Liebermann, succeeded in artificially producing this dyestuff from anthracene, a component of coal-tar. The artificial dyestuff being perfectly pure and free from those contaminations which render the use of madder difficult, it soon was preferred to the latter, which it has at present nearly completely displaced.

The discovery of alizarine red was soon followed by those of alizarine orange, galleine, coeruleine, and, in 1878, of alizarine blue.

The slow adoption of these dyestuffs in the wool-dyeing industry is principally attributable to the deep-rooted distrust of wool dyers against any innovation. This resistance, however, is speedily disappearing, as every manufacturer and dyer trying the new dyestuffs invariably finds that they are in no respect inferior to his fastest dyes produced with indigo and madder, but are simpler to apply and more advantageous for wool.

The alizarine colors are dyed after an old method which is known to every wool dyer. The wool is first boiled for 1½ hours with chromate of potash and tartar, then dyed upon a fresh bath by 2½ to 3 hours' boiling. All alizarine colors (such as those of the Badische Anilin und Soda Fabrik, of Ludwigshafen and Stuttgart; Wm. Pickhardt & Kuttroff, New York, Boston, and Philadelphia, viz.):

Alizarine orange W, for brown orange,
Alizarine red WR, for yellow touch ponceau or scarlet,
Alizarine red WB, for blue touch yellow or scarlet,
Alizarine blue WX and SW, for bright blue,
Alizarine blue WR SRW, for dark reddish blue,
Coeruleine W and SW, for green, and
Galleine W, for dahlia,

are dyed after the same method, which offers the great advantage that all these colors can be dyed upon one bath, and that by their mixture numerous fast colors can be produced. On the ground of numerous careful experiments, the writer recommends the following method, which gives well developed and well fixed colors, viz.:

For 100 kil.--The scoured and washed wool is mordanted by boiling for 1½ hours in a bath containing 3 kil. chromate of potash and 2½ kil. tartar, and lightly rinsed; when it can immediately be dyed. For 1,000 lit. water, 1 lit. acetic acid of about 7° Be. is added to the bath. If the water is very hard, double the quantity of acetic acid, which is indispensable, is added. Then the required quantity of dyestuff is added, well stirred, the wool entered, and the temperature raised to boiling, which is continued for 2½ to 3 hours, that is, until a sample taken does no longer surrender any color to a hot solution of soap. Loose wool and worsted slubbing can be entered at 60° C. (140° F.). In dyeing yarn and piece-goods, however, it is advisable to enter the bath cold, work for about 1/4 hour in the cold, and then slowly to raise the temperature in about one hour to the boiling point. With this precaution, level and thoroughly dyed goods are always obtained. If the wool is entered in a hot bath, or if it is rapidly brought to a boil, the dyestuff is too rapidly fixed by the mordant and is liable to run up unevenly, and, with piece-goods, more superficially. For the same reason the goods must always be well wetted out before entering the bath.

We add some special recipes for the various colors, the mordant for all of them being of 3 per cent. chromate of potash and 2½ per cent. tartar for 100 by weight of dry wool.

1. _Orange, Brown Touch_. 20 kil. wool, mordant with 600 grm. chromate of potash and 500 grm. tartar, dye with 3 kil. alizarine orange W.

2. _Ponceau, Yellow Touch_.

20 kil. wool, mordant as for No. 1, dye with 2 kil. alizarine red WR 20 per cent.

3. _Ponceau, Blue Touch_.

20 kil. wool, mordant like No. 1, dye with 2 kil. alizarine red WB 20 per cent.

4. _Dahlia_.

20 kil. wool, mordant like No. 1, dye with 5 kil. galleine W.

5. _Green_.

20 kil. wool, mordant like No. 1, dye with 6 kil. coeruleine W.

_For Piece-goods._

20 kil cloth, mordant the same, dye with 1 kil. 200 grm. coeruleine SW.

6. _Blue, Bright_.

20 kil. wool, mordant the same, dye with 6 kil. alizarine blue WX.

_For Piece-goods._

20 kil. cloth, mordant the same, dye with 1 kil. 200 grm. alizarine blue SW.

7. _Blue, Dark and Red Touch_.

20 kil. wool, mordant like No. 1, dye with 6 kil. alizarine blue WR.

_For Piece-goods._

20 kil. cloth, mordant the same, dye with 1 kil. 200 grm. alizarine blue SRW.

Particular stress is to be laid upon the great fastness of the alizarine dyes against light and fulling. Besides, these dyestuffs contain nothing whatever injurious to the wool fiber. Sanders, which very much tenders the wool, as every dyer knows, can in all cases be replaced by alizarine red and alizarine orange, making an end to the spinners' frequent complaints about too much waste.

Alizarine blue in particular seems to be destined to replace indigo in the majority of its applications, having at least the same power of resisting light and acids, and relieving the dyer of the troublesome, protracted rinsings required for indigo dyed goods. Every piece-dyer knows that the medium and dark indigo blue goods still rub off, even after eight hours' rinsing; but alizarine blue pieces are perfectly dyed through and clean after one hour of rinsing. Another advantage of alizarine blue and the other alizarine dyestuffs is that they unite with all wood colors, as well as with indigo carmine and all aniline dyestuffs. A fine and cheap dark blue, for instance, is obtained by mordanting the wool as above stated and dyeing (20 kil.) in the second bath with 6 kil. alizarine WX and 2 kil. logwood chips; the wood is added to the bath together with the alizarine blue WX, and the best method is to put it into a bag which is hung in the bath.--_D. Woll.-Gew.; Tex. Colorist._

* * * * *

Papier maché has come of late to be largely used in the manufacture of theatrical properties, and nearly all the magnificent vases, the handsome plaques, the graceful statues, and the superb gold and silver plate seen to-day on the stage are made of that material.

* * * * *

CEMENT PAVING.

The streets of "Old London" at the recent Inventions Exhibition at South Kensington were paved with a material in imitation of old, worn bowlder stones and red, herring-boned brickwork, all in one piece from one side of the street to the other. The composition is made by Wilkes' Metallic Flooring Company, out of a mixture consisting chiefly of iron slag and Portland cement, a compound possessing properties which won the only gold medal given for paving at that Exhibition. At the present time the colonnade in Pall Mall, near Her Majesty's Theater, is being laid with this paving, which is also being extensively used in London and the provinces for roads, tramways, and flooring; the composition is likewise sometimes cast into artistic forms for the ornamentation of buildings, or into slabs for roofing, facing, and other purposes. The subway from the Exhibition to the District Railway is laid with the same material.

The works of the Wilkes Metallic Flooring Company are in the goods yard of the Midland Railway Company at West Kensington. The Portland cement, before it is accepted at the works, is tested by means of an Aidie's machine. The general strain the set cement is required to bear is 750 lb. to the square inch. All samples which will not bear a strain of 500 lb. are rejected. The various iron slags are carefully selected, and rejected when too soft, and at the works a small percentage of black slag, rich in iron, is mixed in with them. The lumps of slag are first crushed in a Mason & Co.'s stone breaker, and then sifted through 1/8 in., 1/4 in., and 1/16 in. wire meshes into these three sizes for mixing. Next the granulated substance is thoroughly well washed with water to remove soluble matter and impalpable dust, and afterward placed where it is protected from the access of dust and dirt. The washing waters carry off some sulphides, as well as mechanical impurities. The Portland cement is not used just as it, comes from the works, but is exposed to the air in a drying room for about fourteen days, and turned over two or three times during that period. The slag is also turned over three times dry and three times wet, and mixed with the Portland cement by means of water containing 5 per cent. of "Reekie" cement to make the whole mass set quickly. The mixture is then turned over twice and put into moulds; each mould is first half filled, and the mixture then hammered down with iron beaters. The rest of the composition is then poured in, beaten down, and the whole mould violently jolted by machinery to shake down the mixture and to get rid of air holes. While it is still wet the casting is taken out of the mould, its edges are cleaned, and after the lapse of one day it is placed in a bath, of silicate of soda. Should the casting be allowed to get dry before it is placed in this bath, no good results would be obtained; it is left in the bath for seven days. When delicate stone carvings have to be copied, the moulds are of a compound of gelatine, from the flexible nature of which material designs much undercut can be reproduced. For the foregoing particulars we are indebted to Mr. William Millar, the working manager at West Kensington. Sometimes the composition is cast in large, heavy slabs, moulded on the top to resemble the surface of roads of granite blocks. A feature of the invention is the rapidity with which the composition sets. For instance, the manager states that a roadway was finished at the Inventions Exhibition at seven o'clock one night, and at six o'clock next morning four or five tons of paper in vans passed over it into the building, without doing any harm to the new road. In laying down roads, much of the preparation of the material is done on the spot, and the composition after being put down unsilicated in a large layer has the required design stamped upon its wet surface by means of wooden or gutta-percha moulds. As regards the durability of the composition, Mr. T. Grover, one of the directors, says that the company guarantees its paving work for ten years, and that the paving, the whole of the ornamental tracings, and some of the other work at Upton Church, Forest Gate, Essex, were executed by means of Wilkes' metallic cement three years ago, and will now bear examination as to its resistance to the action of weather. Some of this paving has been down in Oxford Street, London, for more than six years. Mr. A.R. Robinson, C.E., London agent of the company, states that the North Metropolitan Tramway Company has about 25,000 yards of it in use at the present time, and that the paving is largely used by the War Office for cavalry stables. The latter is a good test, for paving for stables must be non-slippery and have good power of resisting chemical action.

In the Wm. Millar and Christian Fair Nichols patent for "Improvements in the means of accelerating the setting and hardening of cements," they take advantage of the hydraulicity of certain of the salts of magnesia, by which the cements set hard and quickly while wet. For accelerating the setting of cements they use carbonate of soda, alum, and carbonate of ammonia; for indurating or increasing the hardening properties of cements they use chloride of calcium, oxide of magnesia, and chloride of magnesia or bittern water; for obtaining an intense hardness they use oxychloride of magnesia. The inventors do not bind themselves to any fixed proportions, but give the following as the best within their knowledge. For colored concretes for casts or other purposes they use Carbonate of soda, 8.41; carbonate of ammonia, 1.12; chloride of magnesia, 0.28; borax, 0.56; water, 89.63; total, 100.00. For gray concrete for any purpose they use: Alum, 8.46; caustic soda, 0.28; whitening or chalk, 0.56; borax, 0.56; water, 90.14; total, 100.00. For floors or slabs _in situ_ they add to cement, well mixed and incorporated with any required proportion of agglomerate for a base, liquid composition of the following proportions: Oxide of magnesia, 0.29; chloride of magnesia, 0.29; carbonate of soda or alum, 4.74; water, 94.68; total, 100.00. Articles manufactured by the invention are afterward wetted with chloride of calcium and placed in a bath containing a solution of silicate of soda or chloride of calcium. The strength of the chloride of calcium is equal to about 20 deg. specific gravity.

C.A. Wilkes and William Millar's improved "metallic compound for flooring, paving, and other purposes," has for its object to provide a paving compound which is not slippery or liable to soften in hot weather, which sets rapidly, and is durable. To three parts of blast furnace slag are added one part of hydraulic cement and enough water to give the proper consistency. To each gallon of water used is added one part of bittern water--the dregs from the manufacture of sea salt--or one part of brine, or about 5 per cent. of carbonate of soda, and 2½ per cent. of carbonate of ammonia. In the compound they sometimes use potash in the proportion of about 5 per cent. of the carbonate of ammonia and carbonate of soda, and when potash is used with bittern water or brine, the proportion of the latter is correspondingly reduced. The compound is of a blue gray color; but when a more striking color is desired, red or yellow oxide of iron may be added. When more speedy induration is necessary, they add about 1 oz. of copperas to every gallon of compound used. The claim is the admixture of bittern water, carbonate of soda, and carbonate of ammonia with the washed slag and cement.

Another improvement, by C.A. Wilkes, relates, in laying _in situ_ any metallic or other materials for street roadways, to completing the convenience thereof by roughening or grooving the surfaces. The concrete is laid in a plastic condition upon a bed of hard core, broken stone, or preferably rough concrete. For footpaths the material may be laid in convenient sections, say 4 ft. to 8 ft. square and 2 in. to 4 in. thick; and in order to allow for the expansion of the material during the setting of the sections or subsequent variations in temperature, he packs the joints between the sections with a layer of felting cloth or other compressible material, thus forming expansion joints. Sometimes he slightly roughens the surface of the material, to give better foothold to pedestrians. Sometimes the grooving is made in imitation of ordinary granite paving sets. In tramway pavement there are grooves to give a grip to the horses' feet, and a slight camber between the rails. He states that a great advantage in laying a pavement by the method is that, when any repairs are necessary, a piece of the exact size can be manufactured at the works, and stamped to the same pattern as the adjoining pavement, then placed at once in position on the removal of the worn portion, thus saving the time necessary for the setting of the concrete on the spot.--_The Engineer_.

* * * * *

A NEW BLEACHING PROCESS.

In the spring of 1883 a Mr. J.B. Thompson, of New Cross, London, patented a new process of bleaching, the main feature of which consisted in the use of carbonic acid gas in a closed vessel to decompose the chloride of lime. The "chemicking" and "souring" operations he performed at one and the same time. The reactions which took place in his bleaching keir were stated by the inventor as follows:

Cl.\
1. Ca ) + CO_{2} = CaCO_{3} + Cl_{2}.
OCl./

2. OH_{2} + Cl_{2} = (ClH)_{2} + O.

3. CaCO_{3} + (ClH)_{2} = CaCl_{2} + CO_{2} + H_{2}O.

That is, in 1 chloride of lime and carbonic acid react upon each other, producing chalk and nascent chlorine; in 2 the nascent chlorine reacts upon the water of the solution and decomposes it, producing hydrochloric acid and nascent oxygen, which bleaches; in 3 the hydrochloric acid just formed reacts upon chalk formed in 1, and produces calcium chloride and one equivalent of water, and at the same time frees the carbonic acid to be used again in the process of decomposing the chloride of lime.

When the process was first brought to the notice of the Lancashire bleachers, it met with an amount of opposition. Some bleaching chemists declared the process was not patentable, as fully half a century ago carbonic acid was known to decompose chloride of lime. The patentee's answer was emphatic, that carbonic acid gas had never been applied in bleaching before. After some delay one of the largest English cotton bleachers, Messrs. Ainsworth, Son & Co., Halliwell, Bolton, threw open their works for a fair test of the Thompson process on a commercial scale.

The result of trial was so satisfactory that a company was formed to work the patent. Soon after this the well-known authorities on the oxidation of cellulose, Messrs. Cross & Bevan and Mr. Mather, the principal partner in the engineering firm of Mather & Platt, of Salford, Lancashire, joined the company. For the last twelve months these gentlemen have devoted considerable attention to improving the original contrivance of Thompson, and a few weeks since they handed over to Messrs. Ainsworth the machinery and instructions for what they considered the most complete and best process of bleaching that has ever been introduced.

Recently a "demonstration" of the "Mather-Thompson" process of bleaching took place at Halliwell, and to which were invited numerous chemists and practical bleachers. Having been favored with an invitation, I propose to lay before your readers a concise report of the proceedings.

It is usual in this country to give a short preliminary boil to the cloth before it is brought in contact with the alkali, the object being to well scour the cloth from the loose impurities present in the raw fiber and also the added sizing materials. In the new process the waste or spent alkaline liquors of the succeeding process are employed, with the result that the bleaching proper is much facilitated. The economy effected by this change is considerable, but in the next operation, that of saponification, the new process differs even more widely from those generally in use. In England, "market" or "white" bleaching requires a number of operations. There is first the alkaline treatment divided into the two stages or processes of lime stewing and bowking in soda-ash, which only imperfectly breaks down the motes. There is consequently a second round given to the goods, consisting of a bowk in soda-ash, followed by the second and usually final chemicking. There is, therefore, much handling of the cloth, with the consequent increase of time and therefore expense.

Now, in the saponification process, the Mather-Thompson Company claim to have achieved a complete triumph. They use a "steamer keir," the invention of Mr. Mather. This keir is so constructed that it will allow of two wire wagons being run in and the door securely fastened. At the top of the keir is fixed a mechanical appliance for steaming the cloth. The steamer keir process consists essentially in:

1. The application of the alkali in solution and in its most effective form, viz., as caustic alkali, to each portion of fiber in such quantity as to produce the complete result upon that portion.

2. The immediate and sustained action of heat in the most effective form of steam.

Before the cloth is run into the steamer keir on the wire wagons, it is saturated with about twice its weight of a dilute solution of caustic soda (2° to 4° Twaddell = 0.5 to 1% Na_{2}O) at a boiling-temperature, when in the steamer keir it is exposed to an atmosphere of steam at four pounds pressure for five hours. This part of the process is entirely new. The advantage of using caustic soda alone in the one operation, such as I describe, has been long recognized, but hitherto no one has been able to effect this improvement. It will be observed that the Mather-Thompson process does away entirely with the use of lime and soda-ash in at least two boilings and the accessory souring operation. In the space of the five hours necessary for the steamer keir process the goods are thoroughly bottomed and all the motes removed, no matter what be the texture or weight of the cloth. After the cloth is washed in hot water it is removed from the steamer keir, then follows a rinse in cold water, and the goods are ready for the bleaching process.

In passing to the bleaching and whitening process, it may be necessary to say that thus far the original Thompson process has been entirely altered. Now we come to that part of the bleaching operation where the essential feature in Thompson's patent is utilized. The patentee has apparently thoroughly grasped the fact that carbonic acid has great affinity for lime and that it liberates, in its gaseous condition, the hypochlorous acid, which bleaches. The most perfect contact is realized between the _nascent_ hypochlorous acid resulting from its action and the fiber constituent in the exposure of the cloth treated with the bleaching solution to the action of the gas. The order of treatment is as follows:

(1) Saturation with weak chemic (1° Tw.), squeeze,
and passage to gas chamber.
(2) Wash (running).
(3) Soda scald.
(4) Wash.
(5) Repetition of 1, but with weaker chemic (½° Tw.).
(6) Wash.
(7) Scouring.

The whole of the above operations are carried out on a continuous plan, the machinery being the invention of Mr. Mather. The cloth travels along at the rate of sixty or eighty yards a minute, and comes out a splendid white bleach. The company consider, however, that it is necessary in the case of some cloth to give a second treatment with chemic and gas, each of thirty seconds duration, with an intermediate scald in a boiling very dilute alkaline solution. Mr. Thompson originally claimed that the use of carbonic acid gas rendered the employment of a mineral acid for souring unnecessary. It is considered now to be advisable to employ it, and the souring is included, as will be observed, in the continuous operation.

The new process for treating cloth differs materially from that originally proposed by Mr. Thompson. His plan was to use an air-tight keir in conjunction with a gas-holder. It is obvious that the "continuous" process would not answer for yarns; Thompson's keir is, therefore, employed for these and all heavy piece-goods.

Thus far I have given a concise outline of the Mather-Thompson process of bleaching, which, it cannot be denied, differs materially from any system hitherto recommended to the trade. Beyond doubt the goods are as perfectly bleached by this process as by any now in use. The question arises, What pecuniary advantage does it offer? Mr. Manby, the manager of Messrs. Ainsworth, has informed me that he has bleached as much as ten miles of cloth by the new process, and is, therefore, entitled to be heard on the subject of cost. In regard to the consumption of chemicals, he estimates the saving to amount to (in money value) one-fourth; steam (coal), one-half; labor, one-half; water, four-fifths; time, two-thirds.

It might be well to contrast the process formerly employed by Messrs. Ainsworth with that they have recently adopted:

"MATHER-THOMPSON" SYSTEM.

Alkali. Bleach Acid Machine
(chemic). Washes.
/ Saturate.
(1) <
\ Steam.
/ (2) Continuous
| (chemic)
| machine
| (or keir if
(2) < for yarns,
| etc.).
| (2a) Machine or
\ pit sour.
(3) Wash up for
finishing.

ORDINARY SYSTEM.

Alkali. Bleach. Acid Machine
Washes.

(1) Lime stew. (1) Wash.
(2) Sour. (2) "
(3) Gray bowk (3) "
(soda ash).
(4)I Chemic. (4) "
(5) Sour. (5) "
(6) White bowk. (6) "
(7)II Chemic. (7) "
(8) Sour. (8) "

It will be understood that 2 and 2a are merged into a single process by using the "continuous" machine. Of course, it will be understood that the cloth has in each case to be cleansed from size and loose impurities. The "Mather-Thompson" Company claim that their system takes twelve hours in the case of "market" or "white" bleaching. They reckon eight hours for the steaming process and four for bleaching and washing. This has to be compared with the old system, which generally takes forty hours, made up as follows: 8 treatments with reagents and the necessary washings, the former taking four hours and the latter one hour each.

The "Mather-Thompson" system has created considerable commotion in English bleaching circles. It is generally considered that the bleachers throughout the whole country will be compelled to adopt it, so great is the saving in time and cost. In commencing a bleachery, the cost of plant by this system is, I understand, less than by the old processes.--_Textile Colorist_.

* * * * *

INSTRUMENTS FOR DRAWING CURVES.

By Prof. C.W. MacCord, Sc.D.