262 H. L. PAIRCHILD — GEOLOGY UNDER PLANETESIMAL HYPOTHESIS 



own observation and induction and decline to entertain hypotheses at 

 variance with their own science. Another quality will be insistence on 

 satisfactory theories for observed phenomena, instead of resting in old 

 conceptions which do not explain or even may be in opposition to the 

 facts. A difficulty in the past has been that physical geology has de- 

 ferred to an hypothesis of earth genesis which was not good theory nor 

 even a scientific induction, and which has been a hindrance and a burden 

 on the progress of earth science. 



The geology of the future will be made by geologists and not by the 

 philosophers ; and the study of planetary conditions will have one founda- 

 tion in geology, as it is here that the science of worlds has an observa- 

 tional basis. The new geology is even today modifying the old astronomy. 

 The student in cosmic science must have his feet on the earth even if his 

 head is among the stars. 



Discussion 

 edward h. kraus' comments 



u 



. . the statement is made (page 255) that at present there is no 

 satisfactory theory as to the formation of such salt deposits as are found 

 at Stassfurt, Sperenberg, and elsewhere. From the various statements 

 as to the ' physical conditions of sea or lake ' and the ' ariditv of climate ' 

 necessary, it would seem as though the so-called ' bar theory ' of Ochse- 

 nius* had been entirely ignored. This theory was advanced as early as 

 1877, but it is only recently that we Americans f have come to appreciate 

 that according to it neither ' aridity of climate ' nor ' abnormal physical 

 conditions of sea or lake ' are necessary to explain such enormous de- 

 posits as occur at Stassfurt, etcetera. 



" That there may be various deposits of salts, as, for example, the ' an- 

 hydrite region,' ' polyhalite region,' ' Kieserite region, 1 and also a ' Car- 

 nallite region,' likewise that from an ocean water of average composition 

 it is possible to have more than twenty-five different minerals deposited, 

 depending upon their solubility, and also their associates in solution- 

 These and other facts are clearly and satisfactorily handled by the Och- 

 senius theory. X 



" It would seem that with such a satisfactory theory at our command, 

 it is not necessary to question whether these large deposits ' may not be 

 accumulated directly by the eruptive processes.' 



*0. Ochsenius: Die Bildung der Steinsalzlager und ihrer Mutterlaugensalze. Halle, 1877. 

 f.I. F. Kemp: Handbook of Rocks, p. 78; also Hubbard in Geology of Michigan, vol. V, pt. ii, 

 p. ix. 

 {Brauns : Chemische Mineralogie. Leipzig, 189G, p. 340, etc. 



