DIASTROPHISM AND THE FORMATIVE PROCESSES 475 



own and became planetoids. These are regarded as natural results 

 of solar eruptions under exceptional stimulus from a passing body.'' 



As the assigned result of this there arose a very significant 

 series of solar attendants of cognate birth and linked together by 

 gradations, though the extremes were quite highly differentiated. 

 The series, as now presented, ranges from massive hot gaseous 

 planets of low densities, down through intermediary forms, to 

 quite small solid bodies of high densities and altogether devoid of 

 appreciable atmospheres. In mass value the largest planet is 

 several million times the smallest planetoid — probably we could 

 say several billion times, if the lower limit of the planetoids were 

 accurately determined. In Table I this great series is listed in the 

 order of size, neglecting the common distinction between planets, 

 planetoids, and satellites, which is immaterial in this particular 

 study. The physical differences are brought out by groupings. 

 It will be seen that the planets, planetoids, and satellites are 

 notably mixed in the lower part of the list. The gradation would 

 doubtless be much closer and the classes even more intermixed, 

 if the sizes of all the smaller bodies were well enough determined 

 to permit a strictly accurate arrangement of the smaller masses. 

 There are now known to be 26 satellites and upward of 800 planet- 

 oids, most of which seem to be less than 100 miles in diameter. 



While in general there is a notable gradation, there is yet a wide 

 gap between the giant group of gaseous planets and the terrestrial 

 group next below, which are essentially solid but have gaseous 

 envelopes. Within the latter group a somewhat notable difference 

 in mass sets off the earth and Venus from Mars. The scant atmos- 

 phere of the last allies it to the atmosphereless group below and its 

 nucleus not unlikely belonged to that class. 



The differences in the groups suggest that the formative pro- 

 cesses, though of the same type and initiated in the same way, 

 entered in such different proportions into the actual formative work 

 that they gave rise to very divergent results. This tallies with our 

 earlier suggestions that the formative agencies embraced within 



' See the special cases of May 29 and July 15, 1919, outlined in this Journal, 

 Vol. XXXVIII (February-March, 1920), pp. 145-49, or the original description by 

 Pettit, in Astrophys. Jour., Vol. L (October, 1919), pp. 206-19. 



