Chapter VII: MISCELLANEOUS.--Turkish Baths for Horses.--With (4)

Dr. Feussner gives a mathematical analysis of the paths taken by the two polarized rays within the Nicol prism, and finds that the emergent extraordinary ray can include an angular field of 29°, but that this extreme value holds good only for rays incident upon that portion of the end surface which is near to the obtuse corner, and that from thence it gradually decreases until the field includes an angle of only about half the previous amount. He finds, moreover, that, although of course the ray emerges parallel to its direction of incidence, yet that the zone of polarized light is shifted to one side of the central line. Also that the great length of the Nicol--3.28 times its breadth--is not only an inconvenience, but owing to the large pieces of spar thus required for its construction, prisms of any but small size become very expensive. To this it may be added that there is a considerable loss of light by reflection from the first surface, owing to its inclined position in regard to the long axis of the prism.

It is with the view of obviating these defects that the modifications represented in Figs. 2 to 6 have been devised.

2. _The Shortened Nicol Prism_.--This arrangement of the Nicol prism is constructed by Dr. Steeg and Reuter of Homburg v.d.H. For the sake of facility of manufacture, the end surfaces are cleavage planes, and the oblique cut, instead of being perpendicular, makes with these an angle of about 84°. By this alteration the prism becomes shorter, and is now only 2.83 times its breadth; but if Canada balsam is still used as the cement, the field will occupy a very unsymmetrical position in regard to the long axis. If balsam of copaiba is made use of, the index of refraction of which is 1.50, a symmetrical field of about 24° will be obtained. A prism of this kind has also been designed by Prof. B. Hasert of Eisenach (_Pogg. Ann._, cxiii., 189), but its performance appears to be inferior to the above.

3. _The Nicol Prism with Perpendicular Ends._--The terminal surfaces in this prism are perpendicular to the long axis, and the sectional cut makes with them an angle of about 75°. The length of the prism is 3.75 times its breadth, and if the cement has an index of refraction of 1.525, the field is symmetrically disposed, and includes an angle of 27°. Prisms of this kind have been manufactured by Dr. Steeg, Mr. C.D. Ahrens, and others.

4. _The Foucault Prism_ (_Comptes Rendus_, 1857, xlv., 238).--This construction differs from all those hitherto mentioned, in that a film of air is employed between the two cut surfaces as the totally reflecting medium instead of a layer of cement. The two halves of the prism are kept in position, without touching each other, by means of the mounting. The length of the prism is in this way much reduced, and amounts to only 1.528 times its breadth. The end surfaces are cleavage planes, and the sectional cut makes with them an angle of 59°. The field, however, includes not more than about 8°, so that this prism can be used only in the case of nearly parallel rays; and in addition to this the pictures which may be seen through it are to some extent veiled and indistinct, owing to repeated internal reflection.

5. _The Hartnack Prism_ (_Ann. de Ch. et de Physique_, ser. iv., vii., 181).--This form of prism was devised in 1866 by MM. Hartnack and Prazmowiski; the original memoir is a valuable one; a translation of it, with some additions, has lately been published (_Journ. of the R. Microscopical Soc._, June, 1883, 428). It is considered by Dr. Feussner to be the most perfect prism capable of being prepared from calc-spar. The ends of the prism are perpendicular to its length; the section carried through it is in a plane perpendicular to the principal axis of the crystal. The cementing medium is linseed oil, the index of refraction of which is 1.485. This form of prism is certainly not so well known in this country as it deserves to be; a very excellent one, supplied to the present writer by Dr. Steeg is of rectangular form throughout, the terminal surfaces are 19 × 15 mm., and the length 41 mm. The lateral shifting of the field is scarcely perceptible, the prism is perfectly colorless and transparent, and its performance is far superior to that of the ordinary Nicol. The field of view afforded by this construction depends upon the cementing substance used, and also upon the inclination of the sectional cut in regard to the end of the prism; it may vary from 20° to 41°. If the utmost extent of field is not required, the prism may be shortened by lessening the angle of the section, at the expense, however, of interfering with the symmetrical disposition of the field.

6. _The Glan Prism_ (Carl's "Repertorium," xvi., 570, and xvii., 195).--This is a modification of the Foucault, and in a similar manner includes a film of air between the sectional surfaces. The end surfaces and also the cut carried through the prism are parallel to the principal axis of the calc-spar. The ends are normal to the length, and the field includes about 8°. This prism is very short, and may indeed be even shorter than it is broad. It is subject to the same defect as that mentioned in the case of the Foucault, although perhaps not quite to the same extent.

II.--THE NEW POLARIZING PRISM.

This prism differs very considerably from the preceding forms, and consists of a thin plate of a doubly refracting crystal cemented between two wedge-shaped pieces of glass, the terminal faces of which are normal to the length. The external form of the prism may thus be similar to the Hartnack, the calc-spar being replaced by glass. The indices of refraction of the glass and of the cementing medium should correspond with the greater index of refraction of the crystal, and the directions of greatest and least elasticity in the latter must stand in a plane perpendicular to the direction of the section. One of the advantages claimed for the new prism is that, it dispenses with the large and valuable pieces of spar hitherto found necessary; a further advantage being that other crystalline substances may be used in this prism instead of calc-spar. The latter advantage, however, occurs only when the difference between the indices of refraction for the ordinary and extraordinary rays in the particular crystal made use of is greater than in calc-spar. When this is the case, the field becomes enlarged, and the length of the prism is reduced.

The substance which Dr. Feussner has employed as being most suitable for the separating crystal plate is nitrate of soda (_natronsalpeter_), in which the above-mentioned values are [omega] = 1.587 and [eta] = 1.336. It crystallizes in similar form to calcite, and in both cases thin plates obtained by cleavage may be used.

As the cementing substance for the nitrate of soda, a mixture of gum dammar with monobromonaphthalene was used, which afforded an index of refraction of 1.58. In the case of thin plates of calcite, a solid cementing substance of sufficiently high refractive power was not available, and a fluid medium was therefore employed. For this purpose the whole prism was inclosed in a short glass tube with airtight ends, which was filled with monobromonaphthalene. In an experimental prism a mixture of balsam of tolu was made use of, giving a cement with an index of refraction of 1.62, but the low refractive power resulted in a very considerable reduction of the field. The extent and disposition of the field may be varied by altering the inclination at which the crystal lamina is inserted (Fig. 7), and thereby reducing the length of the prism, as in the case of the Hartnack.

In order to obviate the effects of reflection from the internal side surfaces if the prism, the wedge-shaped blocks of glass of which it is built up may be made much broader than would otherwise be necessary; the edges of this extra width are cut obliquely and suitably blackened.

The accompanying diagram (Fig. 8) represents a prism of cylindrical external form constructed in this manner, the lower surface being that of the incident light. In this the field amounts to 30°, and the breadth is about double the length.

Dr. Feussner remarks that a prism similar in some respects to his new arrangement was devised in 1869 by M. Jamin (_Comptes Rendus_, lxviii., 221), who used a thin plate of calc-spar inclosed in a cell filled with bisulphide of carbon; and also by Dr. Zenker, who replaced the liquid in M. Jamin's construction by wedges of flint glass.

Among others, the carefully considered modifications of the Nicol prism which have recently been devised by Prof. S.P. Thompson (_Phil. Mag._, November, 1881, 349, and _Jour. R. Micros. Soc._, August, 1883, 575), and by Mr. R.T. Glazebrook (_Phil. Mag._, May, 1883, 352), do not appear to have been known to Dr. Feussner.

The following tabular view of different forms of polarizing prisms is taken from the conclusion of Dr. Feussner's paper:

---------------------------------------+------+---------+------+------
| |Inclina- |Ratio |
| |tion of | of |
| |section |length|
| |in regard| to |
| |to long |clear |
|Field.|axis. |width.|Fig.
---------------------------------------+------+---------+------+------
I. THE OLD POLARISING PRISMS. | ° | ° | |
1. Nicol's prism. | 29 | 22 | 3.28 | 1
2. Shortened Nicol prism-- | | | |
a. Cemented with Canada balsam.| 13 | 25 | 2.83 | 2
b. Cemented with copaiba " | 24 | 25 | 2.83 | 2
3. Nicol with perpendicular ends-- | | | |
a. With Canada balsam. | 20 | 15 | 3.73 | 3
b. With cement of index of | | | |
refraction of 1.525. | 27 | 15 | 3.73 | 3
4. Foucault's prism. | 8 | 40 | 1.528| 4
5. Hartnack's prism-- | | | |
a. Original form. | 35 | 15.9 | 3.51 |5 _a b_
b. With largest field. | 41.9 | 13.9 | 4.04 |5 _a a_
c. With field of 30°. | 30 | 17.4 | 3.19 |5 _a c_
d. With field of 20°. | 20 | 20.3 | 2.70 |5 _a d_
6. Glan's prism. | 7.9 | 50.3 | 0.831| 6
| | | |
II. THE NEW POLARISING PRISM. | | | |
1. With calc-spar: largest field. | 44 | 13.2 | 4.26 |5 _a a_
2. " field of 30°. | 30 | 17.4 | 3.19 |5 _a c_
3. " field of 20°. | 20 | 20.3 | 2.70 |5 _a d_
4. With nitrate of soda: | | | |
" largest field. | 54 | 16.7 | 3.53 |7 _a a_
5. " field of 30°. | 30 | 24 | 2.25 |7 _a b_
6. " field of 20°. | 20 | 27 | 1.96 |7 _a c_
---------------------------------------+------+---------+------+------

As an analyzing prism of about 6 mm. clear width, and 13.5 mm. long, the new prism is stated by its inventor to be of the most essential service, and it would certainly appear that the arrangement is rather better adapted for small prisms than for those of considerable size. Any means by which a beam of polarized light of large diameter--say 3 to 3½ inches--could be obtained with all the convenience of a Nicol would be a real advance, for spar of sufficient size and purity for such a purpose has become so scarce and therefore so valuable that large prisms are difficult to procure at all. So far as an analyzer is concerned, the experience of the writer of this notice would lead to the opinion that improvements are to be looked for rather in the way of the discovery of an artificial crystal which absorbs one of the polarized rays than by further modifications depending upon total reflection. The researches of Dr. Herapath on iodosulphate of quinine (_Phil. Mag._, March, 1852, 161, and November, 1853, 346) are in this direction; but crystals of the so-called herapathite require great manipulative skill for their production. If these could be readily obtained of sufficient size, they would be invaluable as analyzers.

This opinion is supported by the existence of an inconvenience which attends every form of analyzing prism. It is frequently, and especially in projecting apparatus, required to be placed at the focus of a system of lenses, so that the rays may cross in the interior of the prism. This is an unfavorable position for a prismatic analyzer, and in the case of a powerful beam of light, such as that from the electric arc, the crossing of the rays within the prism is not unattended with danger to the cementing substance, and to the surfaces in contact with it.

PHILIP R. SLEEMAN.

* * * * *

ZIRCON.

By F. STOLBA.

Finely ground zircon is quickly rendered soluble if fused with a mixture of potassium borofluoride and potassium carbonate. The author takes two parts of the former to three of the latter, and prepares an intimate, finely divided mixture, which is kept ready for use.

Of this mixture four parts are taken to one of zircon, thoroughly mixed, and melted in a platinum crucible at a red heat. The mass fuses readily, froths at first and gives off bubbles of gas, and flows then quietly, forming a very fluid melt. If the zircon is finely ground, 15 minutes are sufficient for this operation. The loss of weight is 16 per cent., and is not notably increased on prolonged fusion. It corresponds approximately to the weight of the carbonic anhydride present in the potassium carbonate.

As pungent vapors are given off during fusion, the operation should be conducted under a draught hood. The activity of the mixture in attacking zircon appears from the following experiment: Two zircon crystals, each weighing ½ grm., were introduced into the melted mixture and subjected to prolonged heat. In a short time they decreased perceptibly in size; each of them broke up into two fragments, and within an hour they were entirely dissolved. The melted mass is poured upon a dry metal plate, and when congealed is thrown into water. It is at once intersected with a number of fissures, which facilitate pulverization. This process is the more necessary as the unbroken mass is very slowly attacked by water even on prolonged boiling. The powder is boiled in a large quantity of water so as to remove everything soluble. There is obtained a faintly alkaline solution and a sediment insoluble in water. From the filtrate alkalies throw down zirconium hydroxide, free from iron.

The portion insoluble in water is readily dissolved in hydrofluoric acid, and is converted into zircon potassium fluoride. The chief bulk of the zirconium is found in the aqueous solution in the state of double fluorides. The platinum crucible is not in the least attacked during melting. On the contrary, dirty platinum crucibles may be advantageously cleaned by melting in them a little of the above mentioned mixture.

If finely divided zircon is boiled for a long time with caustic lye, it is perceptibly attacked. It is very probable that in this manner zircon might be entirely dissolved under a pressure of 10 atmospheres.

Potassium borofluoride may be readily prepared from cryolite. Crucibles of nickel seem especially well adapted for the fusion of zircon in caustic alkalies.--_Ber. Boehm. Gesell. Wissenschaft; Chem. News_.

* * * * *

A PROCESS FOR MAKING WROUGHT IRON DIRECT FROM THE ORE.[1]

[Footnote 1: A paper read at the Cincinnati Meeting of the
American Institute of Mining Engineers, by Willard P. Ward, A.M.,
M.E., February, 1884.]

The numerous direct processes which have been patented and brought before the iron masters of the world, differ materially from that now introduced by Mr. Wilson. After a careful examination of his process, I am convinced that Mr. Wilson has succeeded in producing good blooms from iron ore, and I think that I am able to point out theoretically the chief reasons of the success of his method.

Without going deeply into the history of the metal, I may mention the well known fact that wrought iron was extensively used in almost all quarters of the globe, before pig or cast iron was ever produced. Without entering into the details of the processes by which this wrought iron was made, it suffices for my present purpose to say that they were crude, wasteful, and expensive, so that they can be employed to-day only in a very few localities favored with good and cheap ore, fuel, and labor.

The construction of larger furnaces and the employment of higher temperatures led to the production of a highly carbonized, fusible metal, without any special design on the part of the manufacturers in producing it. This pig iron, however, could be used only for a few purposes for which metallic iron was needed; but it was produced cheaply and with little loss of metal, and the attempt to decarbonize this product and bring it into a state in which it could be hammered and welded was soon successfully made. This process of decarbonization, or some modification of it, has successfully held the field against all so-called, direct processes up to the present time. Why? Because the old fashioned bloomeries and Catalan forges could produce blooms only at a high cost, and because the new processes introduced failed to turn out good blooms. Those produced were invariably "red short," that is, they contained unreduced oxide of iron, which prevented the contact of the metallic particles, and rendered the welding together of these particles to form a solid bloom impossible.

The process of puddling cast iron, and transforming it by decarbonization into wrought iron, has, as everybody knows, been in successful practical operation for many years, and the direct process referred to so closely resembles this, that a short description of the theory of puddling is not out of place here.

The material operated on in puddling is iron containing from 2½ to 4 per cent. of carbon. During the first stage of the process this iron is melted down to a fluid bath in the bottom of a reverberatory furnace. Then the oxidation of the carbon contained in the iron commences, and at the same time a fluid, basic cinder, or slag, is produced, which covers a portion of the surface of the metal bath, and prevents too hasty oxidation. This slag results from the union of oxides of iron with the sand adhering to the pigs, and the silica resulting from the oxidation of the silicon contained in the iron.

This cinder now plays a very important part in the process. It takes up the oxides of iron formed by the contact of the oxidizing flame with the exposed portion of the metal bath, and at the same time the carbon of the iron, coming in contact with the under surface of the cinder covering, where it is protected from oxidizing influences, reduces these oxides from the cinder and restores them to the bath in metallic form. This alternate oxidation of exposed metal, and its reduction by the carbon of the cast iron, continues till the carbon is nearly exhausted, when the iron assumes a pasty condition, or "comes to nature," as the puddlers call this change. The charge is then worked up into balls, and removed for treatment in the squeezer, and then hammered or rolled. In the Wilson process the conditions which we have noted in the puddling operation are very closely approximated. Iron ore reduced to a coarse sand is mixed with the proper proportion of charcoal or coke dust, and the mixture fed into upright retorts placed in the chimney of the puddling furnace. By exposure for 24 hours to the heat of the waste gases from the furnace, in the presence of solid carbon, a considerable portion of the oxygen of the ore is removed, but little or no metallic iron is formed. The ore is then drawn from the deoxidizer into the rear or second hearth of the puddling furnace, situated below it, where it is exposed for 20 minutes to a much higher temperature than that of the deoxidizer. Here the presence of the solid carbon, mixed with the ore, prevents any oxidizing action, and the temperature of the mass is raised to a point at which the cinder begins to form. Then the charge is carried forward by the workmen to the front hearth, in which the temperature of a puddling furnace prevails. Here the cinder melts, and at the same time the solid carbon reacts on the oxygen remaining combined with the ore, and forms metallic iron; but by this time the molten cinder is present to prevent undue oxidation of the metal formed, and solid carbon is still present in the mixture to play the same role, of reducing protoxide of iron from the cinder, as the carbon of the cast iron does in the ordinary puddling process. I have said that the cast iron used as the material for puddling contains about 3 per cent. of carbon; but in this process sufficient carbon is added to effect the reduction of the ore to a metallic state, and leave enough in the mass to play the part of the carbon of the cast iron when the metallic stage has been reached.

It would be interesting to compare the Wilson with the numerous other direct processes to which allusion has already been made, but there have been so many of them, and the data concerning them are so incomplete, that this is impossible. Two processes, however, the Blair and the Siemens, have attracted sufficient attention, and are sufficiently modern to deserve notice. In the Blair process a metallic iron sponge was made from the ore in a closed retort, this sponge cooled down in receptacles from which the air was excluded, to the temperature of the atmosphere, then charged into a puddling furnace and heated for working. In this way (and the same plan essentially has been followed by other inventors), the metallic iron, in the finest possible state of subdivision, is subjected to the more or less oxidizing influences of the flame, without liquid slag to save it from oxidation, and with no carbon present to again reduce the iron oxides from the cinder after it is formed. The loss of metal is consequently very large, but oxides of iron being left in the metal the blooms are invariably "red short."

In the Siemens process pieces of ore of the size of beans or peas, mixed with lime or other fluxing material, form the charge, which is introduced into a rotating furnace; and when this charge has become heated to a bright-red heat, small coal of uniform size is added in sufficient quantity to effect the reduction of the ore.

The size of the pieces of the material employed prevents the intimate mixture of the particles of iron with the particles of carbon, and hence we would, on theoretical grounds, anticipate just what practice has proved, viz., that the reduction is incomplete, and the resulting metal being charged with oxides is red-short. In practice, blooms made by this process have been so red-short that they could not be hammered at all.

It would be impracticable in this process to employ ore and carbon in as fine particles as Wilson does, as a very large portion of the charge would be carried off by the draught, and a sticking of the material to the sides of the rotating furnace could scarcely be avoided. I do not imagine that a division of the material into anything like the supposed size of molecules is necessary; we know that the graphitic carbon in the pig-iron employed in puddling is not so finely divided, but it is much smaller particles than bean or pea size, and by approximating the size of the graphite particles in pig iron, Wilson has succeeded in obtaining good results.

If we examine the utilization of the heat developed by the combustion of a given quantity of coal in this process, and compare it with the result of the combustion of an equivalent amount of fuel in a blast furnace, we shall soon see the theoretical economy of the process. The coal is burned on the grate of the puddling-furnace, to carbonic acid, and the flame is more fully utilized than in an ordinary puddling-furnace, for besides the ordinary hearth there is the second or rear hearth, where additional heat is taken up, and then the products of combustion are further utilized in heating the retorts in which the ore is partly reduced. After this the heat is still further utilized by passing it under the boilers for the generation of steam, and the heat lost in the gases, when they finally escape, is very small. In a blast furnace the carbon is at first burned only to carbonic oxide, and the products of combustion issue mainly in this form from the top of the furnace. Then a portion of the heat resulting from the subsequent burning of these gases is pretty well utilized in making steam to supply the power required about the works, but the rest of the gas can only be utilized for heating the blast, and here there is an enormous waste, the amount of heat returned to the furnace by the heated blast being very small in proportion to the amount generated by the burning of that portion of carbonic oxide expended in heating it, and the gases escape from both the hot-blast and the boilers at a high temperature.

In the direct process under consideration the fuel burned is more completely utilized than in the puddling process, to which the cast iron from the blast furnace is subjected to convert it into wrought iron.

The economy claimed for this process, over the blast furnace and puddling practice for the production of wrought iron, is that nearly all the fuel used in the puddling operation is saved, and that with about the same amount of fuel used in the blast furnace to produce a ton of pig iron, a ton of wrought iron blooms can be made. I had no opportunity of weighing the charges of ore and coal used, but I saw the process in actual operation at Rockaway, N.J. The iron produced was hammered up into good solid blooms, containing but little cinder. The muck-bar made from the blooms was fibrous in fracture, and showed every appearance of good iron. I am informed by the manager of the Sanderson Brothers' steel works, at Syracuse, N.Y., that they purchased blooms made by the Wilson process in 1881-1882, that _none_ of them showed red-shortness, and that they discontinued their use only on account of the injurious action of the titanium they contained on the melting pots. These blooms were made from magnetic sands from the Long Island and Connecticut coasts.

The drawing given shows the construction of the furnace employed. I quote from the published description:

"The upper part, or deoxidizer, is supported on a strong
mantel plate resting on four cast iron columns.

"The retorts and flues are made entirely of fire-brick, from
special patterns. The outside is protected by a wrought iron
jacket made of No. 14 iron. The puddling furnace is of the
ordinary construction, except in the working bottom, which is
made longer to accommodate two charges of ore, and thus
utilize more of the waste heat in reducing the ore to metallic
iron.

"The operation of the furnace is as follows: The pulverized
ore is mixed with 20 per cent. of pulverized charcoal or coke,
and is fed into an elevator which discharges into the hopper
on the deoxidizer leading into the retorts marked C. These
retorts are proportioned so that they will hold ore enough to
run the puddling furnace 24 hours, the time required for
perfect deoxidation. After the retorts are filled, a fire is
started in the furnace, and the products of combustion pass up
through the main flue, or well, B, where they are deflected by
the arch, and pass out through suitable openings, as indicated
by arrows, into the down-takes marked E, and out through an
annular flue, where they are passed under a boiler.

"It will be noticed that the ore is exposed to the waste heat
on three sides of the retorts, and owing to the great surface
so exposed, the ore is very thoroughly deoxidized, and reduced
in the retorts before it is introduced into the puddling
furnace for final reduction. The curved cast iron pipes marked
D are provided with slides, and are for the purpose of
introducing the deoxidized ore into the second bottom of the
furnace. As before stated, the furnace is intended to
accommodate two charges of ore, and as fast as it is balled up
and taken out of the working bottom, the charge remaining in
the second bottom is worked up in the place occupied by the
first charge, and a _new_ charge is introduced. As fast as the
ore is drawn out from the retorts the elevator supplies a new
lot, so that the retorts are always filled, thus making the
process continuous."

The temperature of the charge in the deoxidizer is from 800° to 1,000° F.--_Amer. Engineer._

* * * * *

SOME REMARKS ON THE DETERMINATION OF HARDNESS IN WATERS.

By HERBERT JACKSON.

Having had occasion some short time ago to examine a hard water which owed half its hardness to salts of magnesium, I noticed that the soap test, applied in the usual way, gave a result which differed very much from that obtained by the quantitative estimation of calcium and magnesium. A perfectly normal lather was obtained when soap had been added in quantities sufficient to neutralize 14° of hardness, whereas the water contained salts of calcium and magnesium equivalent, on Clark's scale, to a hardness of 27°.

Although I was aware that similar observations had been made before, I thought that it might be useful to determine the conditions under which the soap test could not be depended upon for reliable results.

I found with waters containing calcium or magnesium alone that, whenever salts of either of these metals were in solution in quantities sufficient to give 23° of hardness on Clark's scale, no dependence could be placed upon the results given by the soap test. In the case of waters containing salts of both calcium and magnesium, I found that if the salts of the latter metal were in solution in quantities sufficient to give more than 10° of hardness, no evidence could be obtained of their presence so long as the salts of calcium in the same water exceeded 6°; in such a case a perfect and permanent lather was produced when soap had been added equivalent to 7° of hardness.

If any water be diluted so as to reduce the proportions of the salts of calcium and magnesium below those stated above, perfectly reliable results will of course be obtained.

Instead of dilution I found that heating the water to about 70° C. was sufficient to cause a complete reaction between the soap and the salts of calcium and magnesium, even if these were present in far larger quantities than any given here.

The experiments so far had all been made with a solution of Castile soap of the strength suggested by Mr. Wanklyn in his book on "Water Analysis." My attention was next directed to the use of any one of the compounds of which such a soap is composed. I commenced with sodium oleate, and found that by employing this substance in a moderately pure condition, perfectly reliable results could be obtained in very hard waters without the trouble of either diluting or heating. I was unable to try sodium stearate directly because of the slight solubility of this substance in cold water or dilute alcohol; but I found that a mixture of sodium oleate and stearate behaved in exactly the same manner as the Castile soap.

I am not prepared at present to state the exact reaction which takes place between salts of calcium and magnesium and a compound soap containing sodium oleate and stearate. I publish these results because I have not noticed anywhere the fact that some waters show a greater hardness with soap when their temperatures approach the boiling point than they do at the average temperature of the air, it being, I believe, the ordinary impression that cold water wastes more soap than hot water before a good and useful lather can be obtained, whereas with very many waters the case is quite the reverse. Neither am I aware at present whether it is well known that the use of sodium oleate unmixed with sodium stearate dispenses with the process of dilution even in very hard waters.--_Chem. News._

* * * * *

THE DENSITY AND PRESSURE OF DETONATING GAS MIXTURES.

MM. Berthelot and Vielle have recently been studying the influence of the density of detonating gaseous mixtures upon the pressure developed. The measure of pressure developed by the same gaseous system, taken under two initial states of different density to which the same quantity of heat is communicated, is an important matter in thermodynamics. If the pressures vary in the same ratio as the densities, we may conclude, independently of all special hypotheses on the laws of gases, first, that the specific heat of the system is independent of its density (that is to say, of its initial pressure), and depends only on the absolute temperature, whatever that may mean; and secondly, that the relative variation of the pressure at constant volume, produced by the introduction of a determinate quantity of heat, is also independent of the pressure, and a function only of the temperature. Lastly, the pressure itself will vary proportionally with the absolute temperature, as defined by the theory of a perfect gas, and will serve to determine it. MM. Berthelot and Vielle operated with a bomb, at first kept at ordinary temperatures in the air, and afterward heated in an oil bath to 153 deg. Cent. They also employed isomeric mixtures of the gases; methylic ether, cyanogen, hydrogen, acetylene, and other gases were experimented upon, and the general conclusions are as follows: 1. The same quantity of heat being furnished to a gaseous system, the pressure of the system varies proportionally to the density of the system. 2. The specific heat of the gas is sensibly independent of the density as well toward very high temperatures as about deg. Cent. This is all true for densities near to those that the gas possesses cold under normal pressure, and which varied in the experiment to double the original value. 3. The pressure increases with the quantity of heat furnished to the same system. 4. The apparent specific heat increases parallel with this quantity of heat. These conclusions are independent of all hypotheses on the nature and laws of gases, and were simply drawn from the experiments in question.

* * * * *

TURKISH BATHS FOR HORSES.

The Turkish bath has become an established institution in this country; men of all classes now use it for sanitary as well as remedial purposes. Athletes of various descriptions find it invaluable in "training," and all the distinguished jockeys and light weights keep themselves in condition by its use.

It was thought probable that what was good for man might also be good for the horse, and the fact has been proved. Messrs. Pickford, the eminent carriers, in their hospital for horses at Finchley, have had a bath in operation over eleven years, and find the horses derive great benefit from its use. The bath is put in operation three days a week, and is administered to over twenty horses in this time. The value of the bath having been thus proved, it is rather strange that it has not been more generally adopted by the large carrying firms. However, the Great Northern Railway Company at their new hospital for horses at Totteridge, are erecting a very complete Turkish bath. It consists of three rooms. First, a large wash room or grooming room, from which is entered the first hot room, or tepidarium, from 140° to 150° Fahr.; from this room, the horse, after being thoroughly acclimated, can, if necessary, pass to the hottest room, or calidarium, from 160° to 170° Fahr., and without any turning round can pass on into the grooming and washing room again. This last room is slightly heated from the two other rooms, and in each are stocks in which the animal can he fastened if required. The heating is done most economically by Constantine's convoluted stove, and thorough ventilation is secured from the large volume of hot air constantly supplied, which passes through the baths, and as it becomes vitiated is drawn off by specially designed outlets. The wash room is supplied with hot and cold water, which can, of course, be mixed to any required temperature.--_Building News._

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|| / / 1ST HOT ROOM ||
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/ =======+ || ||
/ || || CURTAIN||
WASHING ROOM|| |+=========================== =||
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|| \ \ 2ND HOT ROOM || FRESH
|| \ \ || / AIR
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|| || | WARM || |
|| ||FOUL AIR FOUL AIR| AIR || |
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* * * * *

MIRYACHIT, A NEWLY DESCRIBED DISEASE OF THE NERVOUS SYSTEM, AND ITS ANALOGUES.[1]

[Footnote 1: Read before the New York Neurological Society,
February 5, 1884.]

By WILLIAM A. HAMMOND, M.D., Surgeon-General, U.S. Army (Retired List); Professor of Diseases of the Mind and Nervous System in the New York Post-Graduate Medical School and Hospital.

In a very interesting account of a journey from the Pacific Ocean through Asia to the United States, by Lieutenant B.H. Buckingham and Ensigns George C. Foulk and Walter McLean,[2] United States navy, I find an affection of the nervous system described which, on account of its remarkable characteristics, as well as by reason of certain known analogies, I think should be brought to the special notice of the medical profession. I quote from the work referred to, the following account of this disease. The party is on the Ussuri River not far from its junction with the Amur in Eastern Siberia: "While we were walking on the bank here we observed our messmate, the captain of the general staff (of the Russian army), approach the steward of the boat suddenly, and, without any apparent reason or remark, clap his hands before his face; instantly the steward clapped _his_ hands in the same manner, put on an angry look, and passed on. The incident was somewhat curious, as it involved a degree of familiarity with the steward hardly to have been expected. After this we observed a number of queer performances of the steward, and finally comprehended the situation. It seemed that he was afflicted with a peculiar mental or nervous disease, which forced him to imitate everything suddenly presented to his senses. Thus, when the captain slapped the paddle-box suddenly in the presence of the steward, the latter instantly gave it a similar thump; or, if any noise were made suddenly, he seemed compelled against his will to imitate it instantly, and with remarkable accuracy. To annoy him, some of the passengers imitated pigs grunting, or called out absurd names; others clapped their hands and shouted, jumped, or threw their hats on the deck suddenly, and the poor steward, suddenly startled, would echo them all precisely, and sometimes several consecutively. Frequently he would expostulate, begging people not to startle him, and again would grow furiously angry, but even in the midst of his passion he would helplessly imitate some ridiculous shout or motion directed at him by his pitiless tormenters. Frequently he shut himself up in his pantry, which was without windows, and locked the door, but even there he could be heard answering the grunts, shouts, or pounds on the bulkhead outside. He was a man of middle age, fair physique, rather intelligent in facial expression, and without the slightest indication in appearance of his disability. As we descended the bank to go on board the steamer, some one gave a loud shout and threw his cap on the ground; looking about for the steward, for the shout was evidently made for his benefit, we saw him violently throw his cap, with a shout, into a chicken-coop, into which he was about to put the result of his foraging expedition among the houses of the stanitza.

[Footnote 2: "Observations upon the Korean Coast, Japanese-Korean
Ports, and Siberia, made during a journey from the Asiatic
Station to the United States, through Siberia to Europe, June 3
to September 8, 1882." Published by the United States Navy
Department, Washington, 1883, pp. 51.]

"We afterward witnessed an incident which illustrated the extent of his disability. The captain of the steamer, running up to him, suddenly clapping his hands at the same time, accidentally slipped and fell hard on the deck; without having been touched by the captain, the steward instantly clapped his bands and shouted, and then, in powerless imitation, he too fell as hard and almost precisely in the same manner and position as the captain. In speaking of the steward's disorder, the captain of the general staff stated that it was not uncommon in Siberia; that he had seen a number of cases of it, and that it was commonest about Yakutsk, where the winter cold is extreme. Both sexes were subject to it, but men much less than women. It was known to Russians by the name of 'miryachit'".

So far as I am aware--and I have looked carefully through several books of travel in Siberia--no account of this curious disease has been hitherto published.

The description given by the naval officers at once, however, brings to mind the remarks made by the late Dr. George M. Beard, before the meeting of the American Neurological Association in 1880, relative to the "Jumpers" or "Jumping Frenchmen" of Maine and northern New Hampshire.[3]

[Footnote 3: "Journal of Nervous and Mental Diseases," vol. vii.,
1880, p. 487.]

In June, 1880, Dr. Beard visited Moosehead Lake, found the "Jumpers," and experimented with them. He ascertained that whatever order was given them was at once obeyed. Thus, one of the jumpers who was sitting in a chair with a knife in his hand was told to throw it, and he threw it quickly, so that it stuck in a beam opposite; at the same time he repeated the order to throw it with a cry of alarm not unlike that of hysteria or epilepsy. He also threw away his pipe, which he was filling with tobacco, when he was slapped upon the shoulder. Two jumpers standing near each other were told to strike, and they struck each other very forcibly. One jumper, when standing by a window, was suddenly commanded by a person on the other side of the window to jump, and he jumped up half a foot from the floor, repeating the order. When the commands are uttered in a quick, loud voice, the jumper repeats the order. When told to strike he strikes, when told to throw he throws whatever he may happen to have in his hand. Dr. Beard tried this power of repetition with the first part of the first line of Virgil's "Æneid" and the first part of the first line of Homer's "Iliad," and out-of-the-way words of the English language with which the jumper could not be familiar, and he repeated or echoed the sound of the word as it came to him in a quick, sharp voice, at the same time he jumped, or struck, or threw, or raised his shoulders, or made some other violent muscular motion. They could not help repeating the word or sound that came from the person that ordered them, any more than they could help striking, dropping, throwing, jumping, or starting; all of these phenomena were indeed but parts of the general condition known as jumping. It was not necessary that the sound should come from a human being; any sudden or unexpected noise, as the explosion of a gun or pistol, the falling of a window, or the slamming of a door--provided it was unexpected and loud enough--would cause these jumpers to exhibit some one or all of these phenomena. One of these jumpers came very near cutting his throat, while shaving, on hearing a door slam. They had been known to strike their fists against a red-hot stove, to jump into the fire and into water. They could not help striking their best friend if near them when ordered. The noise of a steam whistle was especially obnoxious to them. One of these jumpers, when taking some bromide of sodium in a tumbler, was told to throw it, and he dashed the tumbler upon the floor. It was dangerous to startle them in any way when they had an ax or an knife in their hands. All of the jumpers agreed that it tired them to be jumped, and they dreaded it, but they were constantly annoyed by their companions.

From this description it will at once, I think, be perceived that there are striking analogies between "miryachit" and this disorder of the "Jumping Frenchmen" of Maine. Indeed, it appears to me that, if the two affections were carefully studied, it would be found that they were identical, or that, at any rate, the phenomena of the one could readily be developed into those of the others. It is not stated that the subjects of miryachit do what they are told to do. They require an example to reach their brains through the sense of sight or that of hearing, whereas the "Jumpers" do not apparently perform an act which is executed before them, but they require a command. It seems, however, that a "Jumper" starts whenever any sudden noise reaches his ears.

In both classes of cases a suggestion of some kind is required, and then the act takes place independently of the will. There is another analogous condition known by the Germans as _Schlaftrunkenheit_, and to English and American neurologists as somnolentia, or sleep-drunkenness. In this state an individual, on being suddenly awakened, commits some incongruous act of violence, ofttimes a murder. Sometimes this appears to be excited by a dream, but in others no such cause could be discovered.

Thus, a sentry fell asleep during his watch, and, being suddenly aroused by the officer in command, attacked the latter with his sword, and would have killed him but for the interposition of the bystanders. The result of the medical examination was that the act was involuntary, being the result of a violent confusion of mind consequent upon the sudden awaking from a profound sleep. Other cases are cited by Wharton and Stille in their work on medical jurisprudence, by Hoffbauer, and by myself in "Sleep and its Derangements."

The following cases among others have occurred in my own experience:

A gentleman was roused one night by his wife, who heard the street-door bell ring. He got up, and, without paying attention to what she said, dragged the sheets off of the bed, tore them hurriedly into strips, and proceeded to tie the pieces together. She finally succeeded in bringing him to himself, when he said he had thought the house was on fire, and he was providing means for their escape. He did not recollect having had any dream of the kind, but was under the impression that the idea had occurred to him at the instant of his awaking.

Another was suddenly aroused from a sound sleep by the slamming of a window-shutter by the wind. He sprang instantly from his bed, and, seizing a chair that was near, hurled it with all his strength against the window. The noise of the breaking of glass fully awakened him. He explained that he imagined some one was trying to get into the room and had let his pistol fall on the floor, thereby producing the noise which had startled him.

In another case a man dreamed that he heard a voice telling him to jump out of the window. He at once arose, threw open the sash, and jumped to the ground below, fortunately only a distance of about ten feet, so that he was not injured beyond receiving a violent shock. Such a case as this appears to me to be very similar to those described by Dr. Beard in all its essential aspects.

A few years ago I had a gentleman under my charge who would attempt to execute any order given him while he was asleep by a person whispering into his ear. Thus, if told in this way to shout, he shouted as loud as he could; if ordered to get up, he at once jumped from the bed; if directed to repeat certain words, he said them, and so on.

I am not able to give any certain explanation of the phenomena of miryachit or of the "Jumpers," or of certain of those cases of sleep-drunkenness which seem to be of like character. But they all appear to be due to the fact a motor impulse is excited by perceptions without the necessary concurrence of the volition of the individual to cause the discharge. They are, therefore, analogous to reflex actions, and especially to certain epileptic paroxysms due to reflex irritations. It would seem as though the nerve cells were very much in the condition of a package of dynamite or nitro glycerin, in which a very slight impression is sufficient to effect a discharge of nerve force. They differ, however, from the epileptic paroxysm in the fact that the discharge is consonant with the perception--which is in these cases an irritation--and is hence an apparently logical act, whereas in epilepsy the discharge is more violent, is illogical, and does not cease with the cessation of the irritation.

Certainly the whole subject is of sufficient importance to demand the careful study of competent observers.

* * * * *

THE GUM DISEASE IN TREES.[1]

[Footnote 1: Communicated to the _Medical Times_ by Sir James Paget.]