Chapter II: Methods of Illumination (1)

_Torches_ consist of a bundle of loosely twisted threads which has been immersed in a mixture formed of two parts, by weight, of beeswax, eight of resin, and one of tallow. In warm, dry weather, these torches when lighted last for two hours when at rest, and for an hour and a quarter on a march. A good light is obtained by spacing them 20 or 30 yards apart.

Another style of torch consists of a cardboard cylinder fitted with a composition consisting of 100 parts of saltpeter, 60 of sulphur, 8 of priming powder, and 30 of pulverized glass, the whole sifted and well mixed. This torch, which burns for a quarter of an hour, illuminates a space within a radius of 180 or 200 yards very well.

The _tourteau goudronné_ (lit. "tarred coke") is merely a ring formed of old lunt or of cords well beaten with a mallet (Fig. 10). This ring is first impregnated with a composition formed of 20 parts of black pitch and 1 of tallow, and then with another one formed of equal parts of black pitch and resin. One of these torches will burn for an hour in calm weather, and half an hour in the wind. Rain does not affect the burning of it. These rings are usually arranged in pairs on brackets with two branches and an upper circle, the whole of iron, and these brackets are spaced a hundred yards apart.

A _tarred fascine_ consists of a small fagot of dry wood, 20 inches in length by 4 in diameter, covered with the same composition as the preceding (Fig. 11). Fascines thus prepared burn for about half an hour. They are placed upright in supports, and these latter are located at intervals of twenty yards.

The _Lamarre compositions_ are all formed of a combustible substance, such as boiled oil,[1] of a substance that burns, such as chlorate of potash, and of various coloring salts.

[Footnote 1: For preparation see page 9304 of SUPPLEMENT.]

The _white composition_ used for charging fire balls and 1½ inch flambeaux is formed of 500 parts of powdered chlorate of potash, 1,500 of nitrate of baryta, 120 of light wood charcoal, and 250 of boiled oil. Another white composition, used for charging ¾ inch flambeaux, consists of 1,000 parts of chlorate of potash, 1,000 of nitrate of baryta, and 175 of boiled oil.

The _red composition_ used for making red flambeaux and percussion signals consists of 1,800 parts of chlorate of potash, 300 of oxalate of strontia, 300 of carbonate of strontia, 48 of whitewood charcoal, 240 of boiled oil, 6 of oil, and 14 of gum lac.

A red or white _Lamarre flambeau_ consists of a sheet rubber tube filled with one of the above-named compositions. The lower extremity of this tube is closed with a cork. When the charging has been effected, the flambeau is primed by inserting a quickmatch in the composition. This is simply lighted with a match or a live coal. The composition of the Lamarre quickmatch will be given hereafter.

A Lamarre flambeau 1½ inch in diameter and 3 inches in length will burn for about thirty-five minutes. One of the same length, and ¾ inch in diameter, lasts but a quarter of an hour.

A _fire ball_ consists of an open work sack internally strengthened with a sheet iron shell, and fitted with the Lamarre white composition. After the charging has been done, the sphere is wound with string, which is made to adhere by means of tar, and canvas is then wrapped around the whole. Projectiles of this kind, which have diameters of 6, 8, 11, and 13 inches, are shot from mortars.

The _illuminating grenade_ (Fig. 13) consists of a sphere of vulcanized rubber, two inches in diameter, charged with the Lamarre white composition. The sphere contains an aperture to allow of the insertion of a fuse. The priming is effected by means of a tin tube filled with a composition consisting of three parts of priming powder, two of sulphur, and one of saltpeter. These grenades are thrown either by hand or with a sling, and they may likewise be shot from mortars. Each of these projectiles illuminates a circle thirty feet in diameter for a space of time that varies, according to the wind, from sixty to eighty seconds.

The _percussion signal_ (Fig. 14) consists of a cylinder of zinc, one inch in diameter and one and a quarter inch in length, filled with Lamarre red composition. It is provided with a wooden handle, and the fuse consists of a capsule which is exploded by striking it against some rough object. This signal burns for nearly a minute.

_Belgian illuminating balls and cylinders_ are canvas bags filled with certain compositions. The cylinders, five inches in diameter and seven in length, are charged with a mixture of six parts of sulphur, two of priming powder, one of antimony, and two of beeswax cut up into thin slices. They are primed with a quickmatch. The balls, one and a half inch in diameter, are charged with a composition consisting of twelve parts of saltpeter, eight of sulphur, four of priming powder, two of sawdust, two of beeswax, and two of tallow. They are thrown by hand. They burn for six minutes.

_Illuminating kegs_ (Fig. 15) consist of powder kegs filled with shavings covered with pitch. An aperture two or three inches in diameter is made in each head, and then a large number of holes, half an inch in diameter, and arranged quincuncially, are bored in the staves and heads. All these apertures are filled with port-fires.

The _illuminating rocket_ (Fig. 17) consists of a sheet iron cartridge, _a_, containing a composition designed to give it motion, of a cylinder, _b_, of sheet iron, capped with a cone of the same material and containing illuminating stars of Lamarre composition and an explosive for expelling them, and, finally, of a directing stick, _c_. Priming is effected by means of a bunch of quickmatches inclosed in a cardboard tube placed in contact with the propelling composition. This latter is the same as that used in signal rockets. As in the case of the latter, a space is left in the axis of the cartridges. These rockets are fired from a trough placed at an inclination of fifty or sixty degrees. Those of three inches illuminate the earth for a distance of 900 yards. They may be used to advantage in the operation of signaling.

A _parachute fire_ is a device designed to be ejected from a pot at the end of the rocket's travel, and to emit a bright light during its slow descent. It consists of a small cylindrical cardboard box (Fig. 16) filled with common star paste or Lamarre stars, and attached to a parachute, _e_, by means of a small brass chain, _d_.

To make this parachute, we cut a circle ten feet in diameter out of a piece of calico, and divide its circumference into ten or twelve equal parts. At each point of division we attach a piece of fine hempen cord about three feet in length, and connect these cords with each other, as well as with the suspension chain, by ligatures that are protected against the fire by means of balls of sized paper.

In rockets designed to receive these parachutes, a small cavity is reserved at the extremity of the cartridge for the reception of 225 grains of powder. To fill the pot, the chain, _d_, is rolled spirally around the box, _c_, and the latter is covered with the parachute, _e_, which has been folded in plaits, and then folded lengthwise alternately in one direction and the other.

The _parachute port-fire_ consists of a cardboard tube of from quarter to half an inch in diameter, and from four to five inches in length, closed at one extremity and filled with star paste. This is connected by a brass wire with a cotton parachute eight inches in diameter. A rocket pot is capable of holding twenty of these port-fires.

Parachute fires and port-fires are used to advantage in the operation of signaling.--_La Nature_.

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IMPROVEMENT IN LAYING OUT FRAMES OF VESSELS--THE FRAME TRACER.

By GUSTAVE SONNENBURG.

To avoid the long and time-consuming laying out of a boat by ordinates and abscissas, I have constructed a handy apparatus, by which it is possible without much trouble to obtain the sections of a vessel graphically and sufficiently accurate. The description of its construction is given with reference to the accompanying cut. A is a wooden rod of rectangular section, to which are adapted two brackets, a_{1} a_{2}, lined with India rubber or leather; a_{1} is fixed to the wood, a_{2} is of metal, and, like the movable block of a slide gauge, moves along A. In the same plane is a second rod, perpendicular to A, and attached thereto, which is perforated by a number of holes. A revolving pin, C, is adapted to pass through these holes, to which a socket, D, is pivoted, C acting as its axis. To prevent this pin from falling out, it is secured by a nut behind the rod. Through the socket, D, runs a rod, E, which carries the guide point, s_{1}, and pencil, s_{2}. Over s_{1} a rubber band is stretched, to prevent injury to the varnish of the boat. Back of and to A and B a drawing board is attached, over which a sheet of paper is stretched.

The method of obtaining a section line is as follows: The rod, A, is placed across the gunwale and perpendicular to the axis of the boat, and its anterior vertical face is adjusted to each frame of the boat which it is desired to reproduce. By means of the brackets, a_{1} and a_{2}, A is fixed in place. The bolt, C, is now placed in the perforations already alluded to, which are recognized as most available for producing the constructional diagram. At the same time the position of the pencil point, s_{2}, must be chosen for obtaining the best results.

Next the operator moves along the side of the boat the sharpened end, s_{1}, of the rod, E, and thus for the curve from keel to gunwale, s_{2} describes a construction line. It is at once evident that a_{2}, for example, corresponds to the point, a_{1}. The apparatus is now removed and placed on the working floor. If, reversing things, the point, s_{1}, is carried around the construction curve, the point, s_{2}, will inscribe the desired section in its natural dimensions. This operation is best conducted after one has chosen and described all the construction curves of the boat. Next, the different section lines are determined, one by one, by the reversed method above described. The result is a half section of the boat; the other symmetrical half is easily obtained.

If the whole process is repeated for the other side of the boat, tracing paper being used instead of drawing paper, the boat may be tested for symmetry of building, a good control for the value of the ship. For measuring boats, as for clubs and regattas, for seamen, and often for the so-called _Spranzen_ (copying) of English models, my apparatus, I doubt not, will be very useful.--_Neuste Erfindungen und Erfahrungen_.

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TAR FOR FIRING RETORTS.

The attention of gas engineers has been forcibly directed to the use of tar as a fuel for the firing of retorts, now that this once high-priced material is suffering, like everything else (but, perhaps, to a more marked extent), by what is called "depression in trade." In fact, it has in many places reached so low a commercial value that it is profitable to burn it as a fuel. Happily, this is not the case at Nottingham; and our interest in tar as a fuel is more experimental, in view of what may happen if a further fall in tar products sets in. I have abandoned the use of steam injection for our experimental tar fires in favor of another system. The steam injectors produce excellent heats, but are rather intermittent in their action, and the steam they require is a serious item, and not always available.

Tar being a _pseudo_ liquid fuel, in arranging for its combustion one has to provide for the 20 to 25 per cent. of solid carbon which it contains, and which is deposited in the furnace as a kind of coke or breeze on the distillation of the volatile portions, which are much more easily consumed than the tar coke.

THE TAR FIRE

I have adopted is one that can be readily adapted to an ordinary coke furnace, and be as readily removed, leaving the furnace as before. The diagram conveys some idea of the method adopted. An iron frame, d, standing on legs on the floor just in front of the furnace door, carries three fire tiles on iron bearers. The top one, a, is not moved, and serves to shield the upper face of the tile, b, from the fierce heat radiated from the furnace, and also causes the air that rushes into the furnace between the tiles, a and b, to travel over the upper face of the tile, b, on which the tar flows, thereby keeping it cool, and preventing the tar from bursting into flame until it reaches the edge of the tile, b, over the whole edge of which it is made to run fairly well by a distributing arrangement. A rapid combustion takes place here, but some unconsumed tar falls on to the bed below. About one-third of the grate area is filled up by a fire tile, and on this the tar coke falls. The tile, c, is moved away from time to time, and the tar coke that accumulates in front of it is pushed back on to the fire bars, e, at the back of the furnace, to be there consumed. Air is thus admitted, by three narrow slot-like openings, to the front of the furnace between the tiles, a, b, and c, and under c and through the fire bars, e. The air openings below are about three times the area of the openings in the front of the furnace; but as the openings between the fire bars and the tiles are always more or less covered by tar coke, it is impossible to say what the effective openings are. This disposition answers admirably, and requires little attention. Three minutes per hour per fire seems to be the average, and the labor is of a very light kind, consisting of clearing the passages between the tiles, and occasionally pushing back the coke on to the fire bars. These latter are not interfered with, and will not require cleaning unless any bricks in the furnace have been melted, when a bed of slag will be found on them.

THE AMOUNT OF DRAUGHT

required for these fires is very small, and less than with coke firing. I find that 0.08 in. vacuum is sufficient with tar fires, and 0.25 in. for coke fires. The fires would require less attention with more draught and larger tar supply, as the apertures do not so easily close with a sharp draught, and the tar is better carried forward into the furnace. A regular feed of tar is required, and considerable difficulty seems to have been experienced in obtaining this. So long as we employed ordinary forms of taps or valves, so long (even with filtration) did we experience difficulties with the flow of viscous tar. But on the construction of valves specially designed for the regulation of its flow, the difficulty immediately disappeared, and there is no longer the slightest trouble on this account. The labor connected with the feeding of furnaces with coke and cleaning fires from clinker is of a very arduous and heavy nature. Eight coke fires are normally considered to be work for one man. A lad could work sixteen of these tar fires.

COMPOSITION OF FURNACE GASES.

Considerable attention has been paid to the composition of the furnace gases from the tar fires. The slightest deficiency in the air supply, of course, results in the immediate production of smoke, so that the damper must be set to provide always a sufficient air supply. Under these circumstances of damper, the following analyses of combustion gases from tar fires have been obtained:

No Smoke.
CO_{2}. O. CO.
11.7 5.0 Not determined.
13.3 3.7 "
10.8 5.4 "
14.8 2.5 "
13.5 3.0 "
12.4 5.6 "
12.4 4.6 "
13.1 5.9 "
15.3 1.0 "
10.8 4.0 "
14.0 2.8 "
______ ______
Average 12.9 3.9
(11 analyses) ______ ______
11.5 Not determined.
14.3 "
14.6 "

Damper adjusted so that a slight smoke was observable in the combustion gases.

CO_{2}. O. CO.
17.30 None. Not determined.
16.60 " "
16.50 0.1 "
15.80 0.1 "
16.20 1.8 0.7
_______ _____ _____
Average 16.48 0.4 0.7

--_Gas Engineer_.

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A NEW MERCURY PUMP.

The mercury pumps now in use, whether those of Geissler, Alvergniat, Toepler, or Sprengel, although possessed of considerable advantages, have also serious defects. For instance, Geissler's pump requires a considerable number of taps, that of Alvergniat and Toepler is very fragile in consequence of its complicated system of tubes connected together, and that of Sprengel is only suitable for certain purposes.

The new mercury pump constructed by Messrs. Greisser and Friedrichs, at Stutzerbach, is remarkable for simplicity of construction and for the ease with which it is manipulated, and also because it enables us to arrive at a perfect vacuum.

The characteristic of this pump is, according to _La Lumiere Electrique_, a tap of peculiar construction. It has two tubes placed obliquely in respect to its axis, which, when we turn this tap 90 or 180 degrees, are brought opposite one of the three openings in the body of the tap.

Thus the striæ that are formed between the hollowed-out parts of the tap do not affect its tightness; and, besides, the turns of the tap have for their principal positions 90 and 180 degrees, instead of 45 and 90 degrees, as in Geissler's pump.

The working of the apparatus, which only requires the manipulation of a single tap, is very simple. When the mercury is raised, the tap is turned in such a manner that the surplus of the liquid can pass into the enlarged appendage, a, placed above the tap, and communication is then cut off by turning the tap to 90 degrees.

The mercury reservoir having descended, the bulb empties itself, and then the tap is turned on again, in order to establish communication with the exhausting tube. The tap is then closed, the mercury ascends again, and this action keeps on repeating.

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NO ELECTRICITY FROM THE CONDENSATION OF VAPOR.--It has been maintained by Palmieri and others that the condensation of vapor results in the production of an electrical charge. Herr S. Kalischer has renewed his investigations upon this point, and believes that he has proved that no electricity results from such condensation. Atmospheric vapor was condensed upon a vessel coated with tin foil, filled with ice, carefully insulated, and connected with a very sensitive electrometer. No evidence could be obtained of electricity.--_Ann. der Physik und Chemie_.

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THE ELECTRO-MAGNETIC TELEPHONE TRANSMITTER.

An interesting contribution was made by M. Mercadier in a recent number of the _Comptes Rendus de l'Academie Francaise_. On the ground of some novel and some already accepted experimental evidence, M. Mercadier holds that the mechanism by virtue of which the telephonic diaphragms execute their movements is analogous to, if not identical with, that by which solid bodies of any form, a wall for instance, transmit to one of their surfaces all the vibratory movements of any kind which are produced in the air in contact with the other surface. It is a phenomenon or resonance. Movements corresponding to particular sounds may be superposed in slender diaphragms, but this superposition must necessarily be disturbing under all but exceptional circumstances. In proof of this view, it is cited that diaphragms much too rigid, or charged with irregularly distributed masses over the surface, or pierced with holes, or otherwise evidently unfitted for the purpose, are available for transmission. They will likewise serve when feathers, wool, wood, metals, mica, and other substances to the thickness of four inches are placed between the diaphragm and the source of vibratory movement. The magnetic field does not alter these relations in any way. The real diaphragm may be removed altogether. It is sufficient to replace it by a few grains of iron filings thrown on the pole covered with a piece of pasteboard or paper. Such a telephone works distinctly although feebly; but any slender flexible disk, metallic or not, spread over across the opening of the cover of the instrument, with one or two tenths of a gramme (three grains) of iron filings, will yield results of increased and even ordinary intensity. This is the iron filing telephone, which is reversible; for a given magnetic field there is a certain weight of iron filings for maximum intensity. It appears thus that the advantage of the iron diaphragm over iron filings reduces itself to presenting in a certain volume a much more considerable number of magnetic molecules to the action of the field. The iron diaphragm increases the telephonic intensity, but it is by no means indispensable.

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ON ELECTRO-DISSOLUTION, AND ITS USE AS REGARDS ANALYSIS.

By H.N. WARREN, Research Analyst.

On the same principle that electro-dissolution is used for the estimation of combined carbon in steel, etc., I have lately varied the experiment by introducing, instead of steel, iron containing a certain percentage of boron, and, having connected the respective boride with the positive pole of a powerful battery, and to the negative a plate of platinum, using as a solvent dilute sulphuric acid, I observed, after the lapse of about twelve hours, the iron had entirely passed into solution, and a considerable amount of brownish precipitate had collected at the bottom of the vessel, intercepted by flakes of graphite and carbon; the precipitate, having been collected on a filter paper, washed, and dried, on examination proved to be amorphous boron, containing graphite and other impurities, which had become chemically introduced during the preparation of the boron compound. The boron was next introduced into a small clay crucible, and intensely heated in a current of hydrogen gas, for the purpose of rendering it more dense and destroying its pyrophoric properties, and was lastly introduced into a combustion tubing, heated to bright redness, and a stream of dry carbonic anhydride passed over it, in order to separate the carbon, finally pure boron being obtained.

In like manner silicon-eisen, containing 9 per cent. of silicon, was treated, but not giving so satisfactory a result. A small quantity only of silicon separates in the uncombined form, the greater quantity separating in the form of silica, SiO_{2}, the amorphous silicon so obtained apparently being more prone to oxidation than the boron so obtained.

Ferrous sulphide was next similarly treated, and gave, after the lapse of a few hours, a copious blackish precipitation of sulphur, and possessing properties similar to the sulphur obtained by dissolving sulphides such as cupric sulphide in dilute nitric acid, in all other respects resembling common sulphur.

Phosphides of iron, zinc, etc., were next introduced, and gave, besides carbon and other impurities, a residue containing a large percentage of phosphorus, which differed from ordinary phosphorus with respect to its insolubility in carbon disulphide, and which resembled the reaction in the case with silicon-eisen rather than that of the boron compound, insomuch that a large quantity of the phosphorus had passed into solution.

A rod of impure copper, containing arsenic, iron, zinc, and other impurities, was next substituted, using hydrochloric acid as a solvent in place of sulphuric acid. In the course of a day the copper had entirely dissolved and precipitated itself on the negative electrode, the impurities remaining in solution. The copper, after having been washed, dried, and weighed, gave identical results with regard to percentage with a careful gravimetric estimation. I have lately used this method, and obtained excellent results with respect to the analysis of commercial copper, especially in the estimation of small quantities of arsenic, thus enabling the experimenter to perform his investigation on a much larger quantity than when precipitation is resorted to, at the same time avoiding the precipitated copper carrying down with it the arsenic. I have in this manner detected arsenic in commercial copper when all other methods have totally failed. I have also found the above method especially applicable with respect to the analysis of brass.

With respect to ammoniacal dissolution, which I will briefly mention, a rod composed of an alloy of copper and silver was experimented upon, the copper becoming entirely dissolved and precipitating itself on the platinum electrode, the whole of the silver remaining suspended to the positive electrode in an aborescent form. Arsenide of zinc was similarly treated, the arsenic becoming precipitated in like manner on the platinum electrode. Various other alloys, being experimented upon, gave similar results.

I may also, in the last instance, mention that I have found the above methods of electro-dissolution peculiarly adapted for the preparation of unstable compounds such as stannic nitrate, potassic ferrate, ferric acetate, which are decomposed on the application of heat, and in some instances have succeeded by the following means of crystallizing the resulting compound obtained.--_Chem. News_.

* * * * *

A NEWLY DISCOVERED SUBSTANCE IN URINE.

Dr. Leo's researches on sugar in urine are interesting, and tend to correct the commonly accepted views on the subject. Professor Scheibler, a chemist well known for his researches on sugar, has observed that the determination of the quantity of that substance contained in a liquid gives different results, according as it is done by Trommer's method or with the polariscope. As sugar nowadays is exclusively dealt with according to the degree of polarization, this fact is of enormous value in trade. Scheibler has isolated a substance that is more powerful in that respect than grape sugar. Dr. Leo's researches yield analogous results, though in a different field. He has examined a great quantity of diabetic urine after three different methods, namely, Trommer's (alkaline solution of copper); by fermentation; and with the polarization apparatus. In many cases the results agreed, while in others there was a considerable difference.

He succeeded in isolating a substance corresponding in its chemical composition to grape sugar, and also a carbo-hydrate differing considerably from grape sugar, and turning the plane of polarization to the left. The power of reduction of this newly discovered substance is to that of grape sugar as 1:2.48. Dr. Leo found this substance in three specimens of diabetic urine, but it was absent in normal urine, although a great amount was examined for that purpose. From this it may be concluded that the substance does not originate outside the organism, and that it is a pathological product. The theory of Dr. Jaques Meyer, of Carlsbad, that it may be connected with obesity, is negatived by the fact that of the three persons in whom this substance was found, only one was corpulent.

* * * * *

FURNACE FOR DECOMPOSING CHLORIDE OF MAGNESIUM.

The problem of decomposing chloride of magnesium is one which has attracted the attention of technical chemists for many years. The solution of this problem would be of great importance to the alkali trade, and, consequently, to nearly every industry. The late Mr. Weldon made many experiments on this subject, but without any particular success. Of late a furnace has been patented in Germany, by A. Vogt, which is worked on a principle similar to that applied to salt cake furnaces; but with this difference, that in place of the pot it has a revolving drum, and instead of the roaster a furnace with a number of shelves. The heating gases are furnished by a producer, and pass from below upward over the shelves, S, then through the channel, C, into the drum, D, which contains the concentrated chloride of magnesium. When the latter has solidified, but before being to any extent decomposed, it is removed from the drum and placed on the top shelf of the furnace. It is then gradually removed one shelf lower as the decomposition increases, until it arrives at the bottom shelf, where it is completely decomposed in the state of magnesia, which is emptied through, E. The drum, D, after being emptied, is again filled with concentrated solution of chloride of magnesium. The hydrochloric acid leaves through F and G. If, instead of hydrochloric acid, chlorine is to be evolved, it is necessary to heat the furnace by means of hot air, as otherwise the carbonic acid in the gases from the generator would prevent the formation of bleaching powder. The air is heated in two regenerating chambers, which are placed below the furnace.--_Industries_.

* * * * *

THE FILTRATION AND THE SECRETION THEORY.

At a recent meeting of the Physiological Society, Dr. J. Munk reported on experiments instituted by him in the course of the last two years with a view of arriving at an experimental decision between the two theories of the secretion of urine--the filtration theory of Ludwig and the secretion theory of Heidenhain. According to the first theory, the blood pressure prescribed the measure for the urine secretion; according to the second theory, the urine got secreted from the secretory epithelial cells of the kidneys, and the quantity of the matter secreted was dependent on the rate of movement of the circulation of the blood. The speaker had instituted his experiments on excided but living kidneys, through which he conducted defibrinized blood of the same animals, under pressures which he was able to vary at pleasure between 80 mm. and 190 mm. Fifty experiments on dogs whose blood and kidneys were, during the experiment, kept at 40° C., yielded the result that the blood of starving animals induced no secretion of urine, which on the other hand showed itself in copious quantities where normal blood was conducted through the kidney. If to the famished blood was added one of the substances contained as ultimate products of digestion in the blood, such, for example, as urea, then did the secretion ensue.

The fluid dropping from the ureter contained more urea than did the blood. That fluid was therefore no filtrate, but a secretion. An enhancement of the pressure of the blood flowing through the kidney had no influence on the quantity of the secretion passing away. An increased rate of movement on the part of the blood, on the other hand, increased in equal degree the quantity of urine. On a solution of common salt or of mere serum sanguinis being poured through the kidney, no secretion followed. All these facts, involving the exclusion of the possibility of a central influence being exercised from, the heart or from the nervous system on the kidneys, were deemed by the speaker arguments proving that the urine was secreted by the renal epithelial cells. A series of diuretics was next tried, in order to establish whether they operated in the way of stimulus centrally on the heart or peripherally on the renal cells. Digitalis was a central diuretic. Common salt, on the other hand, was a peripheral diuretic. Added in the portion of 2 per cent. to the blood, it increased the quantity of urine eight to fifteen fold. Even in much less doses, it was a powerful diuretic. In a similar manner, if yet not so intensely, operated saltpeter and coffeine, as also urea and pilocarpine. On the introduction, however, of the last substance into the blood, the rate of circulation was accelerated in an equal measure as was the quantity of urine increased, so that in this case the increase in the quantity of urine was, perhaps, exclusively conditioned by the greater speed in the movement of the blood. On the other hand, the quantity of secreted urine was reduced when morphine or strychine was administered to the blood. In the case of the application of strychnine, the rate in the current of the blood was retarded in a proportion equal to the reduction in the secretion of the urine.

The speaker had, finally, demonstrated the synthesis of hippuric acid and sulphate of phenol in the excided kidney as a function of its cells, by adding to the blood pouring through the kidney, in the first place, benzoic acid and glycol; in the second place, phenol and sulphate of soda. In order that these syntheses might make their appearance in the excided kidney, the presence of the blood corpuscles was not necessary, though, indeed, the presence of oxygen in the blood was indispensable.

* * * * *

VARYING CYLINDRICAL LENS.

By TEMPEST ANDERSON, M.D., B. Sc.

The author has had constructed a cylindrical lens in which the axis remains constant in direction and amount of refraction, while the refraction in the meridian at right angles to this varies continuously.

A cone may be regarded as a succession of cylinders of different diameters graduating into one another by exceedingly small steps, so that if a short enough portion be considered, its curvature at any point may be regarded as cylindrical. A lens with one side plane and the other ground on a conical tool is therefore a concave cylindrical lens varying in concavity at different parts according to the diameter of the cone at the corresponding part. Two such lenses mounted with axes parallel and with curvatures varying in opposite directions produce a compound cylindrical lens, whose refraction in the direction of the axes is zero, and whose refraction in the meridian at right angles to this is at any point the sum of the refractions of the two lenses. This sum is nearly constant for a considerable distance along the axis so long as the same position of the lenses is maintained. If the lenses be slid one over the other in the direction of their axes, this sum changes, and we have a varying cylindrical lens. The lens is graduated by marking on the frame the relative position of the lenses when cylindrical lenses of known power are neutralized.

Lenses were exhibited to the Royal Society, London, varying from to -6 DCy, and from to +6 DCy.

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THE LAWS OF THE ABSORPTION OF LIGHT IN CRYSTALS.

By H. BECQUEREL.

1. The absorption spectrum observed through a crystal varies with the direction of the rectilinear luminous vibration which propagates itself in this crystal. 2. The bands or rays observed through the same crystal have, in the spectrum, fixed positions, their intensity alone varying. 3. For a given band or ray there exist in the crystal three rectangular directions of symmetry, according to one of which the band generally disappears, so that for a suitable direction of the luminous vibrations the crystal no longer absorbs the radiations corresponding to the region of the spectrum where the band question appeared. These three directions may be called the principal directions of absorption, relative to this band. 4. In the orthorhombic crystals, by a necessary consequence of crystalline symmetry, the principal directions of absorption of all the bands coincide with the three axes of symmetry. We may thus observe three principal absorption spectra. In uniaxial crystals the number of absorption spectra is reduced to two. 5. In clinorhombic crystals one of the principal directions of absorption of each crystal coincides with the only axis of symmetry; the two other principal rectangular directions of each band may be found variously disposed in the plane normal to this axis. Most commonly these principal directions are very near to the principal corresponding directions of optical elasticity. 6. In various crystals the characters of the absorption phenomena differ strikingly from those which we might expect to find after an examination of the optical properties of the crystal. We have just seen that in clinorhombic crystals the principal absorption directions of certain bands were completely different from the axis of optical elasticity of the crystal for the corresponding radiations. If we examine this anomaly, we perceive that the crystals manifesting these effects are complex bodies, formed of various matters, one, or sometimes several, of which absorb light and give each different absorption bands. Now, M. De Senarmont has shown that the geometric isomorphism of certain substances does not necessarily involve identity of optical properties, and in particular in the directions of the axes of optical elasticity in relation to the geometric directions of the crystal. In a crystal containing a mixture of isomorphous substances, each substance brings its own influence, which may be made to predominate in turn according to the proportions of the mixture. We may, therefore, admit that the molecules of each substance enter into the crystal retaining all the optical properties which they would have if each crystallized separately. The principal directions of optical elasticity are given by the resultant of the actions which each of the component substances exerts on the propagation of light, while the absorption of a given region of the spectrum is due to a single one of these substances, and may have for its directions of symmetry the directions which it would have in the absorbing molecule supposing it isolated. It may happen that these directions do not coincide with the axes of optical elasticity of the compound crystal. If such is the cause of the anomaly of certain principal directions of absorption, the bands which present these anomalies must belong to substances different from those which yield bands having other principal directions of absorption. If so, we are in possession of a novel method of spectral analysis, which permits us to distinguish in certain crystals bands belonging to different matters, isomorphous, but not having the same optical properties. Two bands appearing in a crystal with common characters, but presenting in another crystal characters essentially different, must also be ascribed to two different bodies.

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[Continued from SUPPLEMENT, No. 585, page 9345.]

HISTORY OF THE WORLD'S POSTAL SERVICE.

It is commonly believed in Europe that the mail is chiefly forwarded by the railroads; but this is only partially the case, as the largest portion of the mails is intrusted now, as formerly, to foot messengers. How long this will last is of course uncertain, as the present postal service seems suitable enough for the needs of the people. The first task of the mail is naturally the collection of letters. Fig. 17 represents a letter box in a level country.

By way of example, it is not uninteresting to know that the inhabitants of Hanover in Germany made great opposition to the introduction of letter boxes, for the moral reason that they could be used to carry on forbidden correspondence, and that consequently all letters should be delivered personally to the post master.

After the letters are collected, the sorting for the place of destination follows, and Fig. 18 represents the sorting room in the Berlin Post Office. A feverish sort of life is led here day and night, as deficient addresses must be completed, and the illegible ones deciphered.

It may here be mentioned that the delivery of letters to each floor of apartment houses is limited chiefly to Austria and Germany. In France and England, the letters are delivered to the janitor or else thrown into the letter box placed in the hall.

After the letters are arranged, then comes the transportation of them by means of the railroad, the chaise, or gig, and finally the dog mail, as seen in Fig. 19. It is hard to believe that this primitive vehicle is useful for sending mail that is especially urgent, and yet it is used in the northern part of Canada. Drawn by three or four dogs, it glides swiftly over the snow.

It is indeed a large jump from free America, the home of the most unlimited progress, into the Flowery Kingdom, where cues are worn, but we hope our readers are willing to accompany us, in order to have the pleasure of seeing how rapidly a Chinese mail carrier (Fig. 20) trots along his route under his sun umbrella.

Only the largest and most robust pedestrians are chosen for service, and they are obliged to pass through a severe course of training before they can lay any claim to the dignified name, "Thousand Mile Horse."

But even the Chinese carrier may not strike us so curiously as another associate, given in our next picture, Fig. 21, and yet he is a European employe from the Landes department of highly cultivated France. The inhabitants of this country buckle stilts on to their feet, so as to make their way faster through brambles and underbrush which surrounds them. The mail carrier copied them in his equipment, and thus he goes around on stilts, provided with a large cane to help him keep his balance, and furnishes a correct example of a post office official suiting the demands of every district.

While the mail in Europe has but little to do with the transportation of passengers, it is important in its activity in this respect in the large Russian empire.

The tarantass (Fig. 22), drawn by three nimble horses, flies through the endless deserts with wind-like rapidity.

The next illustration (Fig. 23) leads us to a much more remote and deserted country, "Post office on the Booby Island," occupied only by birds, and a hut containing a box in which are pens, paper, ink, and wafers. The mariners put their letters in the box, and look in to see if there is anything there addressed to them, then they continue their journey.

Postage stamps are not demanded in this ideal post office, but provision is made for the shipwrecked, by a notice informing them where they can find means of nourishment.

Once again we make a leap. The Bosnian mail carrier's equipment (Fig. 24) is, or rather was, quite singular, for our picture was taken before the occupation.

This mounted mail carrier with his weapons gives one the impression of a robber.

The task of conducting the mail through the Alps of Switzerland (Fig. 25) must be uncomfortable in winter, when the sledges glide by fearful precipices and over snow-covered passes.

Since the tariff union mail developed from the Prussian mail, and the world's mail from the tariff union, it seems suitable to close our series of pictures by representing the old Prussian postal service (Fig. 26) carried on by soldier postmen in the eighteenth century during the reign of Frederick the Great.

The complaint is made that poetry is wanting in our era, and it has certainly disappeared from the postal service. One remembers that the postilion was for quite a while the favorite hero of our poets, the best of whom have sung to his praises, and given space to his melancholy thoughts of modern times in which he is pushed aside. It is too true that the post horn, formerly blown by a postilion, is now silenced, that the horse has not been able to keep up in the race with the world in its use of the steam horse, and yet how much poetry there is in that little post office all alone by itself on the Booby Island, that we have described--the sublimest poetry, that of love for mankind!

The poet of the modern postal system has not yet appeared; but he will find plenty of material. He will be able to depict the dangers a postman passes through in discharging his duty on the field, he will sing the praises of those who are injured in a railroad disaster, and yet continue their good work.

He can also praise the noble thought of uniting the nations, which assumed its first tangible form in the world's mail. It will not be a sentimental song, but one full of power and indicative of our own time, in spite of those who scorn it.--_Translated for the Scientific American Supplement by Jenny H. Beach, from Neue Illustrirte Zeitung_.

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ON NICKEL PLATING.

By THOMAS T.P. BRUCE WARREN.

The compound used principally for the electro-deposition of nickel is a double sulphate of nickel and ammonia. The silvery appearance of the deposit depends mainly on the purity of the salt as well as the anodes. The condition of the bath, as to age, temperature, and degree of saturation, position of anodes, strength of current, and other details of manipulation, which require care, cleanliness, and experience, such as may be met with in any intelligent workman fairly acquainted with his business, are easily acquired.

In the present paper I shall deal principally with the chemical department of this subject, and shall briefly introduce, where necessary, allusion to the mechanical and electrical details connected with the process. At a future time I shall be glad to enlarge upon this part of the subject, with a view of making the article complete.

A short time ago nickel plating was nearly as expensive as silver plating. This is explained by the fact that only a few people, at least in this country, were expert in the mechanical portions of the process, and only a very few chemists gave attention to the matter. To this must be added that our text-books were fearfully deficient in information bearing on this subject.

The salt used, and also the anodes, were originally introduced into this country from America, and latterly from Germany. I am not aware of any English manufacturer who makes a specialty in the way of anodes. This is a matter on which we can hardly congratulate ourselves, as a well known London firm some time ago supplied me with my first experimental anodes, which were in every way very superior to the German or American productions. Although the price paid per pound was greater, the plates themselves were cheaper on account of their lesser thickness.

The texture of the inner portions of these foreign anodes would lead one to infer that the metallurgy of nickel was very primitive. A good homogeneous plate can be produced, still the spongy, rotten plates of foreign manufacture were allowed the free run of our markets. The German plates are, in my opinion, more compact than the American. A serious fault with plates of earlier manufacture was their crumpled condition after a little use. This involved a difficulty in cleaning them when necessary. The English plates were not open to this objection; in fact, when the outer surfaces were planed away, they remained perfectly smooth and compact.

Large plates have been known to disintegrate and fall to pieces after being used for some time. A large anode surface, compared with that of the article to be plated, is of paramount importance. The tank should be sufficiently wide to take the largest article for plating, and to admit of the anodes being moved nearer to or further from the article. In this way the necessary electrical resistance can very conveniently be inserted between the anode and cathode surfaces. The elimination of hydrogen from the cathode must be avoided, or at any rate must not accumulate. Moving the article being plated, while in the bath, taking care not to break the electrical contacts, is a good security against a streaky or foggy appearance in the deposit.

At one time a mechanical arrangement was made, by which the cathodes were kept in motion. The addition of a little borax to the bath is a great advantage in mitigating the appearance of gas. Its behavior is electrical rather than chemical. If the anode surface is too great, a few plates should be transferred to the cathode bars.

When an article has been nickel plated, it generally presents a dull appearance, resembling frosted silver. To get over this I tried, some time ago, the use of bisulphide of carbon in the same way as used for obtaining a bright silver deposit. Curiously the deposit was very dark, almost black, which could not be buffed or polished bright. But by using a very small quantity of the bisulphide mixture, the plated surfaces were so bright that the use of polishing mops or buffs could be almost dispensed with. When we consider the amount of labor required in polishing a nickel plated article, and the impossibility of finishing off bright an undercut surface, this becomes an important addendum to the nickel plater's list of odds and ends.

This mixture is made precisely in the same way as for bright silvering, but a great deal less is to be added to the bath, about one pint per 100 gallons. It should be well stirred in, after the day's work is done, when the bath will be in proper condition for working next day. The mixture is made by shaking together, in a glass bottle, one ounce bisulphide and one gallon of the plating liquid, allow to stand until excess of bisulphide has settled, and decant the clear liquid for use as required. It is better to add this by degrees than to run the risk of overdoing. If too much is added, the bath is not of necessity spoiled, but it takes a great deal of working to bring it in order again.

About eight ounces of the double sulphate to each gallon of distilled or rain water is a good proportion to use when making up a bath. There is a slight excess with this. It is a mistake to add the salt afterward, when the bath is in good condition. The chloride and cyanide are said to give good results. I can only say that the use of either of these salts has not led to promising results in my hands.

In preparing the double sulphate, English grain nickel is decidedly the best form of metal to use. In practice, old anodes are generally used.

The metal is dissolved in a mixture of nitric and dilute sulphuric acid, with the application of a gentle heat. When sufficient metal has been dissolved, and the unused nitric acid expelled, the salt may be precipitated by a strong solution sulphate of ammonia, or, if much free acid is present, carbonate of ammonia is better to use.

Tin, lead, and portion of the iron, if present, are removed by this method. The silica, carbon, and portions of copper are left behind with the undissolved fragments of metals.

The precipitated salt, after slight washing, is dissolved in water and strong solution ammonia added. A clean iron plate is immersed in the solution to remove any trace of copper. This plate must be cleaned occasionally so as to remove any reduced copper, which will impede its action. As soon as the liquid is free from copper, it is left alkaline and well stirred so as to facilitate peroxidation and removal of iron, which forms a film on the bath. When this ceases, the liquid is rendered neutral by addition of sulphuric acid, and filtered or decanted. The solution, when properly diluted, has sp. gr. about 1.06 at 60° F. It is best to work the bath with a weak current for a short time until the liquid yields a fine white deposit. Too strong a current must be avoided.

If the copper has not been removed, it will deposit on the anodes when the bath is at rest. It should then be removed by scouring.

Copper produces a reddish tinge, which is by no means unpleasant compared with the dazzling whiteness of the nickel deposit. If this is desired, it is far better to use a separate bath, using anodes of suitable composition.

The want of adhesion between the deposited coating and the article need not be feared if cleanliness be attended to and the article, while in the bath, be not touched by the hands.

The bath should be neutral, or nearly so, slightly acid rather than alkaline. It is obvious that, as such a liquid has no detergent action on a soiled surface, scrupulous care must be taken in scouring and rinsing. Boiling alkaline solutions and a free use of powdered pumice and the scrubbing brush must on no account be neglected.

A few words on the construction of the tanks. A stout wood box, which need not be water-tight, is lined with sheet lead, the joints being blown, _not soldered_. An inner casing of wood which projects a few inches above the lead lining is necessary in order to avoid any chance of "short circuiting" or damage to the lead from the accidental falling of anodes or any article which might cut the lead. It is by no means a necessity that the lining should be such as to prevent the liquid getting to the lead.

On a future occasion I hope to supplement this paper with the analysis of the double sulphates used, and an account of the behavior of electrolytically prepared crucibles and dishes as compared with those now in the market.--_Chem. News_.

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CHILLED CAST IRON.