DIASTROPHISM AND THE FORMATIVE PROCESSES 669 



orbit, the second, the inner orbit. The molecule in the inner 

 orbit will get back to ^ in .77 of the time required by the nucleus 

 to reach this point, while the molecule in the outer orbit will 

 require 1.424 times that period, i.e., if it takes the nucleus three 

 hundred and sixty-five days to complete its orbit, the planestesimal 

 that was shot backward and took the inner orbit would reach A 

 eighty-four days ahead of the nucleus, while the molecule that was 

 shot ahead and took the larger orbit would return to A one hundred 



A 



Fig. I. — O.N. represents the orbit of the nucleus; 0.0. P., the orbit of the outer 

 planetesimal; O.I.P., the orbit of the inner planetesimal. Periodic times, earth=i; 

 inner planetesimal = 0.77; outer planetesimal = i .424 (MacMillan). 



and fifty-five days after the nucleus had passed. There was 

 therefore no immediate danger of collision and recapture in either 

 case. Only by waiting for a concurrence of the schedules, which 

 would be liable to be thwarted by perturbations, or by a pro- 

 tracted series of orbital shiftings, or by changes of orbital form 

 or dimensions, could this be brought about. 



Were these planetesimal molecules likely to unite with one 

 another in the course of their flights and so grow to larger sizes? 

 The figure illustrates this point also. It is very obvious that the 

 two planetesimals specified have no opportunity at all to unite 



