Studies for Students 



THE STRUCTURE OF METEORITES. I. 



Those portions of cosmic matter which from time to time 

 fall to the earth and which are known under the general name of 

 meteorites, have now for about a century been objects of collec- 

 tion and study. Earlier studies of this matter were, on account 

 of its limited quantity and variety, necessarily confined chiefly 

 to the description of individual masses. Comparative study, has, 

 therefore, been carried on to only a small extent and the possible 

 knowledge to be gained by investigation along this line is as yet 

 far from complete. The number of localities from which meteor- 

 ites are now known may be stated in round numbers as 550 and 

 the total weight of cosmic matter now preserved and in one way 

 or another available for study, as about 161 tons (146,716 kilo- 

 grams). 



Lines of investigation. — The lines along which the study of 

 meteorites has been and is beinor conducted can be classified as 

 follows, each, of course, being more or less intimately related to or 

 inclusive of the other : (<?) chemical, (#) mineralogical, (c) peno- 

 logical, (d) physical, and (e) structural. Each of these may be 

 ( 1 ) analytical, and (2) synthetical, and may include (3) the study 

 of terrestrial analogies. Of the above courses of investigation 

 the first three have been the lines along which study has been 

 most extensively conducted hitherto. Summarizing briefly their 

 results, it may be stated that the chemical investigation of 

 meteorites has resulted in the identification of twenty-five ele- 

 ments, all similar to those known upon the earth ; the mineralogi- 

 cal in the determination of at least twenty mineral species, some 

 of which are similar and others dissimilar to terrestrial com- 

 pounds, and the petrological in the classification and tabulation 

 of the characters which meteorites display as mineral aggregates. 



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