FORMATION OF MFTEORITES 37Q 



That short-period comets are subject to progressive disinte- 

 gration, and that their scattered elements constitute one class 

 of meteorites, is familiar doctrine. There seems no reason for 

 withholding the conception from comets which have parabolic or 

 hyperbolic orbits, for in certain cases such comets have shown 

 signs of disruption and partial dispersion in their perihelion 

 passages. To the dispersed elements of these comets of high 

 velocity is assigned (in part at least) such meteorites as come to 

 earth from diverse directions with velocities incompatible with 

 an origin within the solar system. 



It remains to consider whether the fragments derived from 

 the disruption of an asteroid, satellite, or small planet through 

 differential gravitative strain without collision, will satisfy the 

 characteristics which meteorites display. Ample data for a judg- 

 ment on this vital point will be found in the articles on the 

 structure of meteorites in the first two numbers of ih.e Journal of 

 Geology for the current year, bv Dr. Farrington, who, at my 

 request, has kindly brought together in succinct and systematic 

 form the essential characteristics of meteoric structure. A study 

 of these characteristics will show that, while they embrace a 

 great and very significant variety, they are all referable to the 

 structures that are appropriate to small planets, while it is diffi- 

 cult to see how all of these characteristics can be found in deriva- 

 tives from any of the alternative sources to which meteorites 

 have been assigned, namely, volcanic action of the moon or of 

 the planets, explosive projection from the sun, or individual 

 aggregation in space. Some of the matter is fragmentary, imply- 

 ing surface conditions, while some of it is coarsely crystalline, 

 implying deep-seated conditions. Some is volatile and com- 

 bustible, implying the absence of high temperature throughout 

 its whole antecedent history, while some as distinctly implies 

 the presence of high temperature. In some meteorites the iron 

 is segregated, while in others it is disseminated. Frequent 

 brecciated structures imply fracturing and recementation. Fault- 

 ing and slickensides demonstrate movements attributable to the 

 parent body, but not to the meteorite itself. Veins imply internal 



