Juke 11, 1909] 



SCIENCE 



937 



glaciated surface, the same numerous lakes, as in 

 Canada, both regions of the earth claiming to be 

 the land of the many thousand lakes. At the 

 border of both regions the horizontal Paleozoic 

 strata begin with an escarpment which is pro- 

 nouncedly developed south of Lake Erie and south 

 of the Gulf of Finland, called here the "glint," 

 and we shall keep this expression to dfesignate 

 similar escarpments. These strata continue far 

 into the interior of Eurasia, and they do the same 

 in North America. 



And again: 



It is very interesting to see how the Appalachian 

 region ends at Newfoundland, forming the project- 

 ing eastern corner of North America, and just 

 opposite in south Ireland, in south Wales, in 

 Cornwall and in Brittany the belt of the old 

 Hercynian Mountains of Europe begins. One 

 seems to be the continuation of the other, and 

 such an excellent geologist as Marcel Bertrand 

 maintained that we have here to deal loith the 

 two ends of one very extensive belt of mountains 

 which extended through the North Atlantic 

 Ocean. But we must not forget that the missing 

 link between hoth ends of these supposed moun- 

 tain chains is longer than their known extent. 

 (The italics are mine.) 



It seems to me that these and other parts 

 of his lecture throw an interesting light on 

 the theory of the moon's terrestrial origin. 

 In brief, the theory is that when the earth had 

 cooled from its molten condition sufficiently 

 to have a crust of solidified matter something 

 like thirty miles thick over its entire surface, 

 it was revolving so rapidly that gravitational 

 attraction and centrifugal force practically 

 balanced each other. For some reason, per- 

 haps some vast and sudden cataclysm, a large 

 portion of this crust was thrown off the 

 earth, and by tidal action was forced gradu- 

 ally outward in a spiral path. In order to 

 form the moon, a mass of this crust about 

 thirty miles thick and of area nearly equal to 

 the combined areas of the present oceans on 

 the earth must have been thrown off. It is 

 supposed that this immense amount of crust 

 was largely taken from the present basin of 

 the Pacific, and that the remaining parts of 

 the earth's crust, while it still floated on a 

 liquid interior, split along an irregular line 

 into two pieces which floated apart, and the 

 gap between these two parts was later filled 



with the waters of the Atlantic, 

 reasons are advanced for the probability of 

 this theory — the fact that the two coasts of 

 the Atlantic have the same contour, the 

 identity between the density of the moon and 

 that of the earth-crust, etc. Professor Penck 

 is evidently not considering this theory at all 

 in his lecture, and yet it seems that what he, 

 approaching the problem from a geographical 

 standpoint, has to say about it, lends a greater 

 probability to the theory. As he says, the 

 Appalachian region ends at Newfoundland, 

 about the latitude of 50° north, and just oppo- 

 site, in Great Britain, on the same latitude, 

 the same region seems to continue. If the 

 theory of the terrestrial origin of the moon, 

 outlined above, be accepted, we can explain 

 this phenomenon much more simply than did 

 Bertrand, and need not suppose the range to 

 extend across the bed of the Atlantic at alL 



Andrew H. Patterson 

 Univeesity op Nobth Caeolina 



SCIENTIFIC BOOKS 

 Scientific Ideas of To-day. A popular accoumt 

 ' of the nature of matter, electricity, light, 



heat, etc., in non-technical language. By 



Charles E. Gibson. Pp. 344; illustrated. 



Philadelphia, J. B. Lippiacott Company. 



1909. 



This book is one which would justify a 

 favorable estimate from almost any other 

 point of view than that which the present 

 reviewer chooses to take. Thus, William E. 

 Eolston gives a favorable estimate of the book 

 in his review of it in Nature; indeed many 

 sections of the book are such as to demand a 

 favorable estimate from any point of view. 

 For example, the description in terms of the 

 electron theory of what takes place when glass 

 is rubbed with sOk or when zinc is dissolved 

 in a voltaic cell (see pages 73-79) is as clear 

 as any one could wish to have it; and in many 

 cases the "scientific ideas of to-day" which 

 are elaborated in the book are applied at once 

 to the analysis of actual phenomena. But 

 some weeks after looking over the book, I came 

 upon what to me seems to be a very significant 

 paper by Professor William James, " On a 



