FIG. 3. 70 80 Scale 24. The method of supporting the straw beam in the centre, so as to secure the maximum sensitiveness without the liability to get out of order, was difficult at first. After trying suspension by fibres of cocoon-silk from a glass frame, suspension on a fine glass axis resting on thin glass rods, and many other devices, I finally adopted the following mode of support: The pointed half of a small sharp needle is broken off about half a millimetre shorter than the internal diameter of the glass tube; the blunt end is then ground very sharp on Arkansas stone. The straw, about seven inches long, having its gravitated masses at the ends, is then balanced on a knife-edge so as to let it roll over to a stable position and to find its centre; and the needle is then run through it at right angles, at such a distance above the horizontal centre of the straw that the centre of gravity of the whole system is a little below the centre of suspension. The beam being slipped into the glass tube (sealed at one end), the needle is supported very delicately against the sides of the glass by its points, and with the least possible amount of friction. It is best now to exhaust temporarily, heating the straw by passing a spirit-flame along the tube, so as to drive off moisture. If, as is almost certain to be the case, one end becomes heavier than the other, equilibrium can be restored, without much difficulty, by holding the spirit-flame for a few seconds under the heavier end, so as to slightly char the straw or other material. When in good adjustment and sufficiently sensitive the balance is ready for experi ment. 25. The material with which I form the masses at the ends includes platinum, brass, silver, lead, bismuth, aluminium, magnesium, glass, selenium, ivory, charcoal of different kinds, straw, cork, and pith. With each of these a large series of experiments were tried, and the experience gained with each was turned to account in making subseqent apparatus. Certain differences, which I shall subsequently allude to, were noticed according to the material forming the gravitating mass; but as soon as I succeeded in obtained the requisite degree of delicacy, the chief results were as decided as they were unexpected. 26. The most delicate apparatus for general experiment is made with a straw beam having pith masses at the end. The general apparatus is shown in the annexed figure (fig. 2): A is the tube belonging to the Sprengel pump. B is the desiccator, full of glass beads moistened with sulphuric acid. c is the tube containing the straw balance with pith ends. It is drawn out to a contracted neck at the end connected with the pump, so as to readily admit of being sealed off if desired at any stage of the exhaustion. D is the pump-gauge, and E is the barometer. 27. The whole being fitted up as here shown, and the apparatus being full of air to begin with, I passed a spiritflame across the lower part of the tube at b, observing the movement by a low-power micrometer; the pith ball (a b) descended slightly, and ther. immediately rose to considerably above its original position. It seemed as if the true action of the heat was one of attraction, instantly overcome by ascending currents of air. A hot metal or glass rod and a tube of hot water applied beneath the pith ball at b produced the same effect as the flame; when ap It is only fair to acknowledge here the assistance which I have received during the progress of these experiments from my young friend and pupil, Mr. Charles H. Gimingham. Without his skill with the blowpipe and delicacy of manipulation with complicated apparatus, it would have been difficult for me to have carried out this investigation during the limited time I am able to devote to original +For a full description of this pump, with diagrams, see Phil. Trans, 1873, vol. clxiii. p. 295. research. NEWS plied above at a, they produced a slight rising of the ball. The same effects take place when the hot body is applied to the other end of the balanced beam. In these cases aircurrents are sufficient to explain the rising of the ball under the influence of heat. 28. In order to apply the heat in a more regular manner, a thermometer was inserted in a glass tube, having at its extremity a glass bulb about 1 inches diameter; it was filled with water and sealed up (see fig. 3). This was arranged on a revolving stand, so that by means of a cord I could bring it to the desired position without moving the eye from the micrometer. The water was kept heated to 70° C., the temperature of the laboratory being about 15° C. 29. The barometer being at 767 millims. and the gauge at zero, the hot bulb was placed beneath the pith ball at b. The ball rose rapidly. As soon as equilibrium was restored I placed the hot-water bulb above the pith ball at a, when it rose again, more slowly, however, than when the heat was applied beneath it. 30. The pump was again set to work; and when the gauge was 147 millims. below the barometer, the experiment was tried again; a similar result, only more feeble, was obtained. The exhaustion was continued, stopping the pump from time to time to observe the effect of heat, when it was seen that the effect of the hot body regularly diminished as the rarefaction increased, until, when the gauge was about 12 millims. below the barometer, the action of the hot body was scarcely noticeable. At 10 millims. below it was still less; whilst when there was only a difference of 7 millims. between the barometer and the gauge, neither the hot-water bulb, the hot rod, nor the spirit-flame caused the ball to move in an appreciable degree. The inference was almost irresistible that the rising of the pith was only due to currents of air, and that at this near approach to a vacuum the residual air was too highly rarefied to have power in its rising to overcome the inertia of the straw beam and the pith balls. A more delicate instrument would doubtless show traces of movement at a still nearer approach to a vacuum; but it seemed evident that when the last trace of air had been removed from the tube surrounding the balance-when the balance was suspended in empty space only-the pith ball would remain motionless, wherever the hot body were applied to it. 31. I continued exhausting. On next applying heat, the result showed that I was far from having discovered the law governing these phenomena; the pith ball rose steadily, and without that hesitation which had been observed at lower rarefactions. With the gauge 3 millims. below the barometer, the ascension of the pith when a hot body was placed beneath it was equal to what it had been in air of ordinary density; whilst with the gauge and barometer level its upward movements were not only sharper than they had been in air, but they took place under the influence of far less heat-the finger, for example, instantly repelling the ball to its fullest extent. To verify these unexpected results, air was gradually let into the apparatus, and observations were taken as the gauge sank. The same effects were produced in inverse order, the point of neutrality being when the gauge was about 7 millims. below a vacuum. (To be continued.) Coal in Patagonia.-G. De Saugainnecourt has discovered extensive deposits of coal on the coast of Patagonia, (lat. 53° 9' 40" north (?); long. 73° 13' 46" west). They extend apparently over 975 hectares and consist of three beds, the highest of which is five metres in thickness. The coal appears to belong to the class of lignites. LECTURES ON THE MORPHOLOGY OF CRYSTALS AT THE CHEMICAL SOCIETY. By NEVIL STORY MASKELYNE, M.A., F.R.S., &c. LECTURE II. PASSING from the case of two axes lying in a plane Mr. Maskelyne proceeded to consider that of three axes in space. They were taken as before to be perpendicular to each other, the point O or origin in which they intersected being taken somewhere in the interior of the crystal. The three faces of the crystal would intersect. A position to the three axes were supposed parallel to three edges in which right of O parallel to the axis of X, or above O parallel to the each case considered as positive. Positions on the oppoaxis of Z, or forward from O parallel to the axis of Y, was in site sides of these to O were considered as negative. A B C and H K L were now supposed to be two faces of the crystal, and they were both supposed to lie in that octant which was included by the three positive directions of the axes. The edge in which they would intersect NEWS If the face HKL be denoted by the symbol (h k l), in the case in the figure this symbol becomes (341), the order of the indices always being taken in that fixed for the axes to which they refer, namely, in the order X Y Z. It is evident, then, that on any crystal when once the axial system is determined on, i.e., when the axes and the face fixing the parameters have been chosen, all that is needed uo determine a face is to know its indices. C hq - k p b ' lp-hra lq- kr' which may be written so that the u, v, and w become in this case [-321]. It was shown by a representation of three perpendicular axes, and of the co-ordinates strained in coloured threads upon it, that the edge in this case represented by its diwere in the proportionate lengths of -3 a on the axis of X, 2 b on the axis of Y, and c on the axis of Z. The indices of the parametral face A B C are evidently (111). Where a face is parallel to an axis, its index is for that axis zero. (340) is the symbol of a plane which inter-rection the diagonal of a parallelepiped, the sides of which a b c cepts ; where represents an indefinitely great 340 magnitude, so that the face H K L would not cut the axis Z as in the figure in a point L, but at an infinite distance, i.e., is parallel to O Z. с O Had either of the points H, K, or L lain on the other side of the centre O to that on which it is in the figure, it would be indicated by a minus sign, and such a sign is placed over the corresponding index. Thus (341) would be the symbol of a face for which the H and L points would lie to the left of O on O X and below O on O Z; K remaining as in the figure. I I I The faces whose edges are parallel to the selected crystallographic axes will have for their symbols (100) or (100) for a face parallel to a plane Y Z containing the axes Y and Z; (010) or (010) for that of the plane Z X, and (001) or (001) for that of the plane X Y. The ratios : : ī might equally easily and with equal truth be thrown into the form of whole numbers; the plane HKL in the figure having then the intercepts 4a3b 12 c. The symbols obtained by using the fractional indices are, however, more simple, and admit in their use of more elegant mathematical expressions and methods of calculation. The meaning of the term coordinates in connection with the three axes was now explained by the lecturer, who further stated that the planes designated by the symbols (hkl) and (pqr) may be represented severally by the expressions which are, in fact, expressive of the relations be tween the parameters abc, the magnitudes hkl (or pqr), involving the ratios of the indices, and the coordinates x y z for any point in the plane; the planes being supposed to be moved parallel to themselves till they passed through the origin, in which case, obviously, their edge must pass through that point. This edge, then, in which these planes intersect would be a line, for each point in which the above two expressions have the same meaning, so that, by first getting rid of x by elimination from the two equations, we get the relation between y and z, the expression becoming On a crystal for every edge formed by a pair of planes there must be an indefinite number of other edges parallel to the edge in question, and it is clear that a plane perpendicular to one of these edges would be perpendicular to them all, and would be perpendicular to the planes to the intersections of which they are due. Such a series of planes forms a zone, and if those planes be each moved parallel to itself till it passes through the origin, all the planes of the zone would intersect in a single line, like the consecutive pages of an open book; that line is called the zone axis, and the plane perpendicular to it is called the zone plane. The expressions [u v w] or, as in the example taken [321] is placed within square braces to a zone. Evidently this zone axis would be identically indicate that it represents a zone axis, and therefore also represented by the edge in which any two planes of the zone would intersect; but it will be found that the actual numerical values thus obtained for the indices in the symbols of one edge in the zone differ in general by a common factor from those in the symbol of a different edge in it. A ready method of obtaining the symbol of a zone from those of any two of its faces was then illustrated. The latter symbols being written, each are repeated in two lines, and the indices of the new symbol being obtained by finding the difference of the products taken diagonally-first, of the second and third indices on the two lines; next, of the third and fourth; and, finally, of the fourth and fifth indices on each line. The next relation illustrated was that connecting the indices of any other plane in the zone with those of the two taken to give the symbol of the zone, .—viz. Then, evw' = wv' f=wu'-u w' g=uv'-vu'. It is clear that these values for e f g must be rational, so that any two zones must be tautohedral in a plane satisfying the condition of rationality which is the condition NEWS necessary for such a plane being a possible face of the crystal. Examples of these laws were given in the case of the zone [111, 341] or [321], which also contains the faces (214) and (012), the edges for which gave symbols differing from each other by common factors, such as -1, 3, and 5. So also this zone [321], and a zone [110, 001], i.e., [110], have in common the face (111) and the face (111). ANALYSIS OF MOFFAT AND HERTFELL SPAS COLLECTED ON THE 5TH AND 12TH OCTOBER, 1874. By W. JOHNSTONE, Edinburgh. Moffat Spa. THIS valuable sulphurous spring, to which Moffat owes its celebrity, was discovered in 1633, and the discoverer is said to have been a daughter of Bishop Whiteford. There are two springs, the upper and the lower, but being only about a yard or so distant, they are regarded as the same well. The springs rush from a cavity of a rock on the brink of a linn, down which rushes a mountain stream. The spring is enclosed by a small square winstone building, the water being collected in a hollow hewn out in the rock, from which it is drawn off by means of a pipe, and handed to the drinkers, containing the following constituents Specific gravity at 60° F. 1001'068 Temperature Temperature of air 64'0° F. Hertfell Spa. 34'508 c.c. 5'325 25.644 2'539 O'999 34'507 This also valuable aluminous sulphate chalybeate, springs from the bottom of a deep rocky ravine on the side of the mountain of the same name. It is distant five miles from Moffat, and there being no regular road part of the way, the generality of the drinkers of it have to obtain their supply from Mr. T. Hetherington, druggist, in the town. Hertfell Spa, which has a strong astringent taste, is most powerful after a fall of rain, and in the greatest perfection when wet is preceded by continued dry weather. It may be preserved for a lengthened period (without the ceremony of hermetical sealing) in a state of purity and efficiency. The spa was discovered by an eccentric individual, named John Williamson, in 1748, and is 1155 feet THE estimation of ammonia by distilling with caustic alkali a known weight of any ammoniacal sait into standard dilute sulphuric acid, and determination of the acid thus neutralised, is one of those processes which are exact enough to satisfy the requirements of the scientific chemist, and capable of such rapidity of execution as to make them invaluable in the hands of the manufacturing chemist. With carefully standardised test acid and alkali solutions the results need not vary more than one or two-tenths per cent. Having had occasion within the last two years to use this volumetric method daily in the examination of gas liquors, and sulphates of ammonia made from the washings of gas oxide of iron, my attention has several times been drawn to some little discrepancies cropping up in spite of the greatest care. In investigating the causes of these differences, the question arose,-does the sulphocyanide present in the sulphate of ammonia as well as in the gas liquor decompose during the distillation under the influence of the excess of alkali? Sulphocyanides submitted to dry distillation with slaked alkalies produce large quantities of ammonia, and it was possible that a similar reaction might take place, though more slowly, at the boiling temperature. To test this point a solution of sulphate of ammonia containing four to five per cent of sulphocyanide was made and used for the following experiments, in which definite quantities were boiled for various lengths of time with different proportions in excess of the liberating alkali. The following results were obtained :UsingCaustic soda Per cent of Ammonia. 23.87 24'19 24'15 23'64 23°47 23.80 23.608 23'97 These results were sufficiently contradictory to confirm my suspicions, and also to raise the doubt that only after the complete removal of the sulphocyanogen could the ammonia be distilled and correctly determined. Before attempting to settle this point I resolved to make sure that there was no defect in the distilling apparatus. This consisted of a twenty-ounce flask, generally filled half full, connected by glass and india-rubber tubing with two bottles, and so arranged that none of the boiling liquid in the flask would be sucked over during sudden condensation. Pure water coloured with delicate pink litmus solution was put into the bottles, and ammonia-free dilute caustic soda solution into the flask; the latter was then boiled into the former. After a few minutes ebullition there was a gradual change in the coloured liquid. It became purple, then blue, and there was thus seen to be manifestly something at fault. The small flask was replaced by a large one, into which the distilling liquid was poured, occupying about half an inch at the bottom; but on slow boiling the same result was obtained, and not only once, but a dozen times. The interposition of a bulbed tube containing broken glass between the flask and bottles made no difference, thus showing that the alkali could not have been carried over mechanically. The same results were also obtained when milk of lime was employed in place of caustic soda, and yet neither of these alkalies could be found in the distillate. The anomaly, however, was soon explained :-On substituting bent glass tubing in place of the glass and india-rubber found so convenient, and continuing the distillation, no alteration in the colour of the pink litmus solution was observed, even after long boiling, and a portion of the distillate subjected to Nessler's test gave no indications of ammonia. When the india-rubber tubing was used once more, the distillate gave a very decided colour to Nessler's solution. Although I have not seen any published records of the absorbent powers of india-rubber tubing for ammonia, I can scarcely believe that it has so long escaped notice; and, considering its wide application, it may not be amiss in me to impress upon others the necessity of restricting its use to the utmost point consistent with flexibility in connecting apparatus. It is quite possible that the materials incorporated with the rubber during the manufacture, as gypsum for example, may be the cause of the disturbance; but this point I have not examined. Having then altered my connecting tubes so as to employ a minimum of india-rubber, I made the following experiments to ascertain the extent of the decomposition of the sulphocyanogen during distillation with various alkalies. A solution of sulphate of ammonia containing 4 per cent of sulphocyanogen was used. The results are as follows: NEWS NOTES ON THE FORMATION AND CONSTITU. TION OF TORBANITE. By WILLIAM SKEY. IN prosecuting experiments previously detailed, upon the evolution of heat caused by mixing dry clay with various liquids, I noticed such an increase of temperature in the case of petroleum that I suspected an absorption of a portion of the matters dissolved in this liquid had occurred, and so was led to investigate the matter further, when the following results were obtained :— (1.) That our commercial kerosenes are nearly or quite decolorised by mixing them with dry clay, and our best native petroleums greatly modified. (2.) That this process is very much quicker when the clay used has been dried at 100° or so C. (3.) That in such a case the clay, if white, acquires a rose and afterwards a black colour, while its streak is light brown. (4.) That torbanite has the same effect as clay. (5.) That the coals I have examined, whether hydrous or anhydrous, do not appear to exercise any absorbent action upon the petroleum oils. (6.) That the same is true of diatomaceous earth (dry), carbonate of lime, and gypsum, hydrous or anhydrous, also pumice-stone and pipe-clay (ignited). (7.) That kerosene which has been completely decolorised by clay, when heated to 100° to 150° C. blackens clay, but has no such effect upon other porous substances, as gypsum, prepared silica, or the light oils of kerosene. (8.) That clay is similarly affected by hot paraffin. (9.) That clay can readily be charged with some of the constituents of petroleum, to such an extent as to have almost the consistence as well as the appearance of torbanite. These results have, I believe, an important bearing upon our present theories as to the formation and constitution of the valuable mineral torbanite. As to the formation of this mineral, it plainly appears from them that clay strata will abstract the colouring matter of petroleum passing through them. If this process is carried on to a small extent we have only a feebly bituminous clay, but if carried on till the clay is saturated, or nearly so, we have a mineral which I believe has exactly the constitution of torbanite. During the formation of this mineral the petroleum passing through it would be purified to a greater or lesser extent. From what has been already stated, I feel sure the absorption is not of a mechanical but of a chemical nature, and this brings me to the next point, that is, the true constitution of the mineral in question, torbanite or boghead coal. As to its constitution, this mineral is associated with the amber group in our best mineralogical works, and the earthy matter is thrown out of the formula. Now this is within small limits uniform in amount in the case of all the samples of this mineral yet analysed, being from 19 to 26 per cent, and it is essentially silicate of alumina that is anhydrous clay. I consider, therefore, the ash of this mineral is not an accidental element as it is now considered, but that it is an essential part of it,-that in fact torbanite is a combination of a bituminous kind of substance with clay, the water of the clay being either substituted by it or a bituminosilicate of alumina formed, which substance may have no affinity or but a very slight one for water. I should state that the coloring matters of petroleum and kerosene are in general terms described as of a bituminous nature-but whether bitumen itself is actually or universally present has not yet been demonstrated. However, these colouring matters are certainly oxidised hydrocarbons, and so class with bitumen and the combustible part of torbanite. |