PRE-TERRESTRIAL HISTORY OF METEORITES 625 



argues against such an origin of their substance, and further, 

 Fouque and Levy produced by cooling from fusion, mineral 

 aggregates as closely resembling meteorites as those made by 

 Meunier from vapors. Again, the crystalline structure of the 

 minerals of meteorites perfectly resembles that of terrestrial 

 minerals known to be produced by cooling from fusion. 



Concerning statement 6 : That the complete crystalline 

 structure possessed by the great majority of iron meteorites 

 indicates a lapse of time sufficient for a slow, uniform arrange- 

 ment of the molecules of their mass, in other words a slow cool- 

 ing, has rarely been doubted. Such a conclusion certainly accords 

 with all terrestrial experience and observation. It has been 

 suggested by Cohen, ^ however, that the crystalline structure 

 expressed in iron meteorites by the Widmanstatten figures may 

 be really a sort of skeleton growth, similar to that seen when 

 needles of ice form over the surface of rapidly cooling water, 

 and that hence the Widmanstatten figures may indicate a rapid 

 crystallization. It is unfortunate that no attempt to reproduce 

 Widmanstatten figures artificially in iron has ever yet succeeded, 

 for if this could be done valuable evidence for judgment on this 

 point could be secured. 



Taking the evidence as it stands, however, and especially 

 taking into consideration iron meteorites like that of La Caille, 

 whose structural features show a complete parallelism through- 

 out a large entire mass, the indications seem to me to point 

 strongly to slow crystallization. Certainly analogies between 

 the formation of crystals in iron and in water should be drawn 

 with hesitation. Iron is far more viscous than water and move- 

 ment in it would take place slowly. Further, the crystalline 

 plates of meteoritic iron differ in composition, showing that time 

 must have elapsed for separation of ingredients as has not taken 

 place in the ice formed upon water. 



Concerning statement 7 : This opinion is based chiefly on 

 the large quantity of glass found in most of the chondritic 

 meteorites, which, it is to be noted, make up by far the larger 



'^ Meteor iten-kunde. Heft I, p. 326. 



