as given by Cohen. As the proportion of phosphorus and copper is higher than in the greater part of Cohen's analyses* in which for the most part weaker acid was employed, it may be presumed that the elements rich in nickel, taenite, schreibersite and the coaly substance, were more strongly attacked, giving an enrichment in nickel. Making allowance for this circumstance, the dissolved portion may be considered as consisting essentially of normal kamacite.

On

The large jagged piece which was only attacked with extreme slowness by cold acid of a strength of 1 to 10 was tried with acid 1 in 5 without much better results in the cold. heating on the water bath vigorous action commenced and continued even after the acid was much diluted. At times the action would continue in the cold after removal from the bath, at others it would almost cease in the hot acid and only recommence with vigor on the addition of a considerable quantity of fresh acid. At other times the action would continue until the acid was completely exhausted and a precipitate began to appear in the solution. These variations in the action of the acid indicate a lack of homogeneity and varying degrees of solubility in different parts of the mass. The residue was similar to that of the original mass except that cohenite was almost entirely lacking. The principal contrast in the two residues was in the greater relative abundance of rhabdite and the less abundance of granular schreibersite and of the coaly matter in that of the jagged piece. The coaly matter was evidently partially destroyed by the action of the hot acid and the residue was entirely freed from it by treatment with strong, cold acid, a white flocculent skeleton remaining. The large piece was broken up as follows: Original specimen

9.1855 grams

Taenite

0.029

0.31%

Schreibersite acicular 0.0255 0-27
(granular 0·0075 0.08%)

0.033

0.35

Non-magnetic residue..

Dissolved...

An analysis of the solution gave the following result (copper was determined in the whole solution, the other elements. in 100ce :)

* Annalen d. K. K. naturhistorischen Hofmuscums, vi, 1891, p. 131; vii, 1892, p. 143; ix, 1894, p. 97.

This composition agrees very nearly with that of the "zackige Stücke" of Toluca given by Cohen, and like that shows a higher proportion of iron and a lower proportion of nickel and cobalt than the general mass of the meteorite and of normal kamacite. The occurrence of rhabdite is not noted in the case of Toluca but may perhaps be presumed from the relatively high percentage of phosphorus.

The non-magnetic residue consisted mainly of rust particles and some dirt evidently derived from laboratory dust. Nothing of any interest that could be referred to the meteorite could be detected in it by microscopic examination.

The small jagged pieces were dissolved in copper-ammonium chloride with the view of determining the amount of carbon but owing to an accident this determination was lost, and only the relative proportion of granular (1.84 per cent) and of acicu lar (1.16 per cent) schreibersite was determined. The amount of the coaly residue was apparently greater than with the treatment with acid. The higher proportion of schreibersite may be referred in part to the slighter action of the solvent, by which more of the original content is recovered, but it is also evident that this mineral, particularly in the acicular form of rhabdite, is more abundant than in the generality of the meteoric mass.

An analysis of taenite, which was dissolved in copperammonium chloride, gave:

In composition as well as in physical aspect (thin, tin-white flexible lamellæ) this agrees very closely with the group rich in nickel and free from carbon of Toluca, Wichita, etc. as given by Cohen. With Toluca also it agrees in the presence of a determinable amount of copper. The phosphorus of the above analysis indicates, as Prof. Cohen has already remarked, that schreibersite is not wholly insoluble in the Cu-Am chloride.

Two analyses of cohenite were made, No. I being the free grains from the general solution of the mass and No. II the vein matter. Both were dissolved in copper-ammonium chloride and the percentages calculated for the difference in weight after deducting the considerable residue of undissolved

schreibersite, separated with the magnet from the carbon, which was determined by burning in a stream of hydrogen and weighing as carbonic acid.

The phosphorus is undoubtedly due to a slight action of the solvent on the schreibersite, which as already remarked is not wholly insoluble in copper ammonium chloride. This result agrees very well with the analyses of cohenite given by Weinschenk and Cohen and with an unpublished analysis of that of Bendegó by Dafert. In appearance the cohenite grains agree with those of Bendegó although they are richer in inclusions of tabular schreibersite. Owing to the general distortion of the crystals and the rounded character of the faces, no measurements could be made, but the forms are undoubtedly identical with those of Bendegó, on which Hussak succeeded in demonstrating that they belong to the cubic system.

Three distinct forms of iron and nickel phosphide occur which although differing greatly in appearance and somewhat also in chemical composition, are probably different phases of a single mineral species. The most abundant individually are the acicular forms known as rhabdite, though, owing to their minute size, they do not equal in weight the granular and

tabular forms known as schreibersite. Both are generally distributed throughout the mass, the schreibersite form being particularly abundant, included in, or adherent to, the surface of the cohenite grains, while the rhabdite needles are especially concentrated in the less soluble metallic portions and in the

spongy, coal-like particles. Both are distinctly crystalline and, as shown in the annexed figure, may occur in the same individual. As Cohen has already shown the chemical identity of the two types, no further proof seems necessary that schreibersite and rhabdite belong to the same mineral species, for which the former name, being the older, should be retained. Diligent search was made without success for crystals that would admit of measurement, the rhabdite individuals being too minute and those of the schreibersite type too much distorted and with strongly rounded faces. The general appearance of the latter type is strongly suggestive of distorted crystals of the cubic system, while the rhabdite needles are apparently tetragonal prisms, although they might also be distorted members of the cubic system. On crystals which will be described later, separated from the São Francisco do Sul mass, Dr. Hussak succeeded in proving that the crystalline. form of schreibersite is really tetragonal.

The third form of phosphide occupies the center of the vein mass being enclosed between walls of cohenite. This is massive and extremely brittle, breaking with a conchoidal fracture and in color and general appearance strongly resembling arsenopyrite. As shown by the analysis below (No. III) the composition differs from that of the typical schreibersite of the same meteorite in the relative proportions of the iron and nickel. The phosphorus is also higher in the complete analysis and approaches more nearly to what Prof. Cohen considers as the normal proportion, but in a separate determination (No. IV) the proportion is nearly the same as in the normal granular schreibersite with a slight admixture of rhabdite needles, Nos. III and IV of the vein matter. In all the material was freed from taenite and cohenite by treatment in copper-ammonium chloride, and in No. II special care was taken in the washing to make sure that the copper found in I and III previously executed, really belonged to the substance and did not come from this solvent.

* The cohenite of the walls of the vein also forms a massive crust covered however with crystalline faces on its outer surface.

The most reliable published analyses of meteoric phosphide, or phosphides, show very variable relative proportions of iron and nickel and cobalt even in the same meteoric mass and as regards phosphorus, a larger group with about 15 to 16 per cent and a small group with about 12 to 13 per cent. The above analyses place Cañon Diablo in the latter group. Copper is only reported in two, Schwetz and Seeläsgen, both of which have been reanalyzed by Cohen with very different results and without copper, which possibly, however, was not looked for. Tin has not been reported, possibly because the solution has usually been made in aqua regia in which it would only appear through a special research. In the present case the solution was made in plain nitric acid and the tin appeared as oxide and was verified by blowpipe tests. The proportion in No. III was certainly as great as in No. II, but was not determined for fear of losing the slight residue before a qualitative test could be made. Curiously enough it did not appear in Nos. I and IV, possibly from the accidental presence of enough chlorine in the nitric acid to dissolve the small amount of stannic oxide as fast as it formed. If this was not the case, it must be presumed that the tin does not belong to the schreibersite but to another mineral that is not generally distributed throughout the meteoric mass, so that it only appears in certain portions of the residue.

As in the course of this investigation, which was mainly undertaken for the purpose of verifying the reported existence of the diamond in the Cañon Diablo meteorite, nothing resembling that substance, or any other form of free carbon, could be detected, it was suspected that possibly the polishing effect produced by the residue of the dissolved mass and attributed to the presence of diamond dust might be due to schreibersite. Owing to the minuteness of the grains and their extreme brittleness, it is difficult to determine the hardness accurately and the figures given (7:01 to 7-22) may be too low. The means at hand were too crude for an accurate test, but apparently distinct scratches were produced on a cleavage plane of topaz and a depolishing effect on the polished face of a cut sapphire. Specimens have been submitted to Mr. George F. Kunz with a request to test the hardness with more perfect appliances, and probably he will report upon them.

The non-magnetic residue consisted for the most part of irregular, black, coke-like particles full of needles of rhabdite. These dissolve quietly in strong hydrochloric acid, setting free the crystals of rhabdite. In strong nitric acid under the microscope there is a rapid evolution of gas that tears the particles to pieces, scattering the rhabdite and leaving an extremely light, whitish flocculent skeleton.