52 STUDIES FOR STUDENTS 



The physical investigation of meteorites has been confined chiefly 

 to studies of their spectra and comparisons of these with the 

 spectra of comets, nebulae, and other heavenly bodies. Studies 

 of thermo-luminescence, magnetism and polarity as exhibited by 

 meteorites have also been made. With the results of the struc- 

 tural studies of meteorites it is the purpose of the present paper 

 to deal in some detail. 



Structure a feature distinguishing meteorites from terrestrial 

 rocks. — It is from the point of view of structure that meteorites 

 differ most completely from terrestrial rocks. In chemical, 

 mineralogical, penological and physical characters some meteor- 

 ites closely resemble terrestrial rocks. The meteorite of Juvinas, 

 for instance, so far as the above characters are concerned, is 

 similar to a basalt, while many of the iron meteorites find a per- 

 fect analogue in the terrestrial irons of Greenland. When the 

 structure of meteorites is considered, however, a distinction is 

 apparent. No resemblance to the clastic texture of the Juvinas 

 meteorite is to be found among terrestrial basalts, nor does 

 the terrestrial nickel-iron show satisfactorily the Widmanstatten 

 figures so characteristic of the iron meteorites. 



It is along this line of study that the geologist finds prob- 

 lems which his science is especially adapted to solve, for the 

 problems afforded are similar in many respects to those included 

 under the group of structural and dynamical, or, as it is some- 

 times termed, phenomenal geology. Just as studies of the latter 

 sort avail to give a knowledge of the forces and conditions under 

 which different rock structures and rock movements are pro- 

 duced, so studies of the structure of meteorites may be expected 

 to discover the conditions under which cosmic matter is formed 

 and the forces to whose action it is subject in space. Since, 

 further, this cosmic matter reaching us as meteorites has striking 

 and important analogies with that, not alone of the crust of the 

 earth, but it may be believed also of its entire substance, the 

 fascinating possibility is presented of reading in the mass of 

 meteorites many chapters in the history of the earth which would 

 otherwise be locked up within its interior. 



