186 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XIII. 



of the first; under II the same after the removal of the iron sulphide and reduction to 100 per cent. Under III is 

 given the composition of the insoluble portion, and under IV the same reduced to 100 per cent. 



Soluble in HC1, Insoluble in HC1. 



I II III IV 



Si0 2 19.15 38.50 24.29 53.80 



A1 2 3 1.95 4.32 



FeO 16.16 23.54 5.41 11.98 



NiO 34 .69 



CoO trace 



MnO 17 .34 trace 



CrO .64 1.41 



CaO 06 .12 1.84 4.08 



MgO 18.31 36.81 10.10 22.37 



K 2 .12 .27 



Na 2 .80 1.77 



S 1.97 



56. 15 100. 00 45. 15 100. 00 



The resuit of the analysis is the usual one since the portion soluble in HC1 has pretty nearly the composition of 

 olivine, while the insoluble shows a mixture of different minerals. The molecular relations of the soluble portion if 

 Ni, Co, and Mn are included with Fe and Ca with Mg figure as follows: 



Si0 2 38.50 : 59.92 =0.643 



FeO 24.57 : 71.84 =.328 



MgO 36.93 : 39.90 =.925 



or E0 2 : RO=0. 643 : 0. 328+0. 925 

 = 1 : 1. 95 



and FeO : MgO= 1 : 2. 820 nearly corresponding to an olivine of the formula of (Fe Mg 3 ) 2 Si0 4 . 



In the insoluble portions chromite is shown by the analysis, also a mineral of the pyroxene group, and perhaps 

 also an asymmetric feldspar. Calculation in a stone of this kind of the constitution is, on account of its very variable 

 composition, of no value and it must therefore be determined by the microscopic analysis given below. Macroscopically 

 the meteorite of Washington has in fracture the characters of a doleritic lava of a dark-gray color, hard and of splintery 

 fracture. Single white radiating chondri, as well as pieces of the same, appear in the black groundmass and in druses 

 iron sulphide crystallizes out. The surface of these crystals is so rounded that they appear melted and measurement 

 is impossible. The material at hand is not sufficient for analysis, although one would be of great value since the light 

 yellow brilliant crystals show no trace of oxidation. The complete solubility in hydrochloric acid, the bright color, 

 and the lack of magnetism indicate troilite. The same mineral is also sprinkled in the whole mass of the meteorite in 

 fine grains. This stone easily takes a polish on account of its great hardness, and the content of nickel-iron, which only 

 slightly appears on fractured surfaces, appears on polished surfaces in numerous grains which vary from minute to 4 

 mm. in diameter. Armored surfaces are beautifully shown in the meteorite, appearing on the polished faces as pretty 

 broad, numerously branched veins which are accompanied by some iron sulphide and crust. On these faces fracture 

 easily occurs. The crust of the meteorite is very hard, black, uneven to swollen, and occasionally 0.8 mm. thick. Its 

 Burface is dull. 



Under the microscope the structure is seen to be porphyrinic. The radiating chondri, also fragments and crystals 

 of different minerals, lie in an irergular granular groundmass which is often so fine grained that it resembles a micro- 

 felsite. The whole appears to be colored by an opaque, dark brown, glassy substance which gives a dark color to the 

 whole. In some chondri these inclusions are lacking and they have a white color. A thin section treated with cold 

 concentrated HC1 becomes colorless and the opaque inclusions become dissolved coloring the acid yellow. Hence 

 there is no carbonaceous substance here and through heating no indication of such appears. Probably it is an amorphous 

 ferrous silicate easily soluble in HCI. The groundmass does not have the character of a tuff but that of a rapidly crys- 

 tallized substance. It shows no detritus of crystals but incomplete crystals and crystal skeletons. Most of the indi- 

 viduals have the form of fragments and show mechanical deformation such as is common in telluric lavas. The most 

 prominent are fragments and crystals of olivine, partly in skeleton forms and seldom with distinct boundaries. The 

 formation of these minerals is different from the ordinary so that it is difficult to determine them with certainty. Also 

 prominent is a great quantity of inclusions of the dark substance so richly present in the groundmass, often arranged 

 parallel to certain crystallographic directions. The outlines of these often appear irregular and without crystallographic 

 boundaries resembling glass inclusions. The cleavage, uncommonly complete for olivine, can be observed, in conse- 

 quence of the rapidity of the crystallization, so that undulatory extinction is a common phenomenon. This property 

 renders the recognition of the minerals difficult. A piece of a thin section exposed to stronger heat caused one mineral 

 to assume a red-brown color and a 'weak pleochroism while the other portions remained unchanged; with cold hydro- 

 chloric acid digesting in 24 hours the regularly arranged inclusions were completely dissolved and only a few black 

 and deep brown octahedral crystals of chromite remained. This is certainly olivine of a composition somewhat different 



