Noll RESEARCHES ON METEORITES— MERRILL. 29 



It is, I think, commonly recognized by all who have givon the matter thought, that greater 

 uniformity in both method and statement of meteorite analyses is desirable. That the prevail- 

 ing practice of separation into soluble and insoluble portions is also desirable is, I believe, with- 

 out question, but the results of these processes can be accepted as little more than suggestive 

 and not final, unless accompanied by a careful and detailed microscopic examination. 



The solution obtained by digestion in distilled water will show with a fair degree of safety, 

 the presence, or absence, of calcium sulphide and ferrous chloride as well as ferrous decomposi- 

 tion products, and the metallic and silicate portions be left practically untouched. The moment 

 an acid is added, however, care needs be exercised in the interpretation of results since one 

 has no means of telling how complete may have been the solution of the "soluble" constituents 

 or the extent to which the "insoluble" may have been attacked. To illustrate: It was found, 

 when working on the olivine of the Admire paUasite, that the material when not reduced to 

 an impalpable powder was not completely dissolved even through repeated digestions over 

 the steam bath in standard hydi'ochloric acid and sodium carbonate solutions, but left, without 

 previous evaporation to dryness, a skeleton residue of white and completely isotropic silica, 

 amounting to some 1.3 per cent of the original material. As showing the approximate propor- 

 tional amounts of tiie olivines and pyroxenes the method is, however, unquestionably useful, 

 particularly when accompanied by the microscopic examination. The late work of Borgstrom, " 

 Prior, *" and Cohen "^ furnishes an excellent example of what may be accomplished, and certainly 

 the carefully detailed analyses of MingayC* leave little to be desired. The practice, %vithin 

 the prescribed limits, of stating what elements were looked for and not found, as well as what 

 were foond, is worthy of commendation and should be followed. Such extremely careful and 

 detailed work as has in times past been done by Fletcher ^ is quite beyond the possibility of 

 general practice, and with the now almost universal use of the microscope is perhaps not essential. 



<■ Der Meteorit von St. Michel, Bull. Com. Geologique de Finland, No. 34, 1912. 



b The Meteoric Stones of Baroti, etc., Min. Mag., Dec, 1913. 



c On the Meteoric Stone which Fell at the Mission ol' St. Marks, etc. Ann. South .\frican Museum, vol. 5, 1903. 



rf Notes on, and analyses of, the Mount Dyrring, Barraba, and Cowra Meteorites. F.ecords Geol. Surv. N. S. Wales, vol. 7, 1904. 



« Min. Mag., vol. 10, No. 43, 1894, and vol. 13, No. 59, 1901. 



o 



