Geology and Mineralogy. 229 



best to those of the earth, that such conclusions, involving the 

 presence of liquid and solid water, and life upon the moon are 

 subject to final acceptance or rejection as problems of physics 

 and biology. The testimony of physics is that no way is known 

 by which water in any form could permanently exist upon the 

 moon except in an extremely minute amount, and of biology 

 that organic evolution operating through all geologic time has 

 been unable to develop any kind of vegetation upon the higher 

 terrestrial mountain summits under conditions which there are 

 strong reasons for believing are much more favorable for life 

 than the most favored portions of the lunar surface. These points 

 are to a considerable extent apart from the main thesis of the 

 paper and would not call for special criticism were it not for 

 their far-reaching importance and the fact that in the past few 

 years the pseudo-scientific columns of some papers have given 

 a certain popular currency to these hypotheses stated without 

 reserve as being facts. 



In conclusion it may be said that this paper marks a step in 

 advance in the study of lunar features, but the reviewer is of the 

 opinion that a better understanding of these selenological enig- 

 mas is finally to come from a rigorous analysis, following a 

 method of multiple hypotheses, which shall use to the fullest 

 extent exact mathematical and physical methods. J. 'b. 



8. Origin of Later ites — In the Geological Magazine for Decem- 

 ber, 1906 (Vol. iii, No. 12, 536-547), Mr. Malcolm Maclaren 

 discusses "The Origin of Certain Laterites." The peculiar fea- 

 tures about laterites which require explanation are their restric- 

 tion geographically and in altitude, their general superficial 

 occurrence and their internal structure — porous, vesicular, piso- 

 litic, or concretionary, their composition as regards the aluminous, 

 ferruginous, or maganiferous hydrates, the general presence of 

 titanium dioxide and the absence of kaolin or silica. The results 

 of the author's field work, supplemented by microscopic examin- 

 ation and chemical analyses, leads to the conclusion "that laterite 

 must be regarded not as the direct product of the decomposition 

 of a rock in siM, but essentially as the replacement of such a 

 decomposition product, for though the ground waters may have 

 derived their mineral content from the underlying rock, they 

 may also have brought it from sources widely separated. A lat- 

 erite may thus result from the individual or combined decom- 

 position of basalts, gneisses, or schists, and there may, in its 

 hardened upper surface, be no particle of the rock whose former 

 place it now occupies." 



The conclusions announced by the writer are as follows: 



" 1 . Lateritic deposits are restricted geographically, because 

 they require for their formation — 



(a) Tropical heat and rain with concomitant abundant vegeta- 

 tion. 



(b) Alternating wet and dry seasons. 



