FUNDAMENTAL PROBLEMS OF GEOLOGY. 1 97 



, their mutual attractious to the extent of such small differences as 

 may arise from their slight differences of velocity and direction of 

 motion. Under extremely favorable conditions of this kind, two 

 meteorites might come into mutual gravitative control and revolve 

 about their common center of gravit^^ Then a third one might join 

 them under like conditions, and so on. The plane of revolution of 

 the third meteorite might chance to correspond with that established 

 by the pair it joined, but more probably it would not. Its direction 

 of revolution might be the same, but more likel}- either transverse in 

 some degree or opposite. It is extremely unlikely that the planes 

 of revolution of any considerable number of meteorites coming thus 

 together would be identical, or that the directions of their revolu- 

 tions would all be coincident, and hence opposite and cross-revolutions 

 would doubtless result, with obvious liability to collisions, so that in 

 the end the swarm might perhaps develop into a quasi-gaseous con- 

 dition, though it might retain a revolutionar}- organization, in which 

 case it would not fall into the class here under consideration. 



It must be noted that the conditions assigned for the starting of 

 the growth of such a swarm are ver}' far from being the usual con- 

 ditions of adjacent meteorites, and hence the accessions to the group 

 in any given period, if the group were started, must be presumed to 

 be few compared to the whole number of meteorites that would pass 

 through the initiating swarm, for of the meteorites that passed the 

 place of the initiating swarm, all those that had opposite or trans- 

 verse courses of any appreciable angle and all those that though 

 moving in parallel directions had appreciably different velocities 

 would traverse the swarm with dangerous contingencies. They 

 would hence be liable to break up the initiating swarm by colliding 

 with its members and driving them be}' ond their mutual gravitative 

 control. This contingency is especially great while the swarm is 

 small and its gravitative command of its members feeble. Hence 

 there arises a serious question whether the swarm's peril of destruc- 

 tion is not greater than its chance of growing to a self-protecting 

 size — so incomparably greater, indeed, as to render the method an 

 improbable one. The dangers of infanc)' in this case seem to be 

 obviously and perilously extreme and the chances of escape ex- 

 ceedingly rare. 



A second serious difficulty in organizing hypothetically a swarm 

 of meteorites from discrete matter primitively diffuse was found to 

 lie in the extreme tenuity of the dispersed celestial matter, whether 

 the present amount of such dispersed matter be considered or the 



