378 



THE POPULAR SCIENCE MONTHLY, 



the true significance of these sand and gravel 

 deposits was not before seen. Mr. Geikie 

 has pointed out that the depos-its occurred 

 during an intermission of the Great Ice Age, 

 when the ice melted and disappeared from 

 the land, which became clothed, instead, 

 with trees and plants, and peopled with ani- 

 mal forms. In the course of ages the arc- 

 tic conditions returned and covered the land 

 again with ice. He has also pointed out 

 that this alternation of temperate and arctic 

 climate has certainly occurred more than 

 once, probably several times. Mr. Geikie's 

 inference becomes still stronger when viewed 

 in the light of Mr. Croll's new theory of a 

 periodic change of climate resulting from 

 the precession of the equinoxes and the in- 

 crease of eccentricity in the earth's orbit. 

 We have no room for an explanation of Mr. 

 CroU's theory, but must content ourselves 

 with referring the reader to Mr. Geikie's 

 book, where he will find it lucidly stated. 



Now, these facts have a very important 

 beai-ing on the history of man. The re- 

 mains that we have gathered of primitive 

 man are divided into paleoUthic, or those 

 belongmg to the Old Stone Period, and 

 neolithic^ or these belonging to the New 

 Stone Period. The paleolithic remains are 

 characterized by the rudest kind of stone 

 implements, implements merely chipped out 

 of stone, without any attempt at finish, and 

 from first to last there is no evidence of im- 

 provement in their make. The neolithic 

 implements, on the other hand, are much 

 better made at the starting-point, and they 

 gradually improve, until they give place to 

 implements of bronze. Again, the paleo- 

 lithic remains are accompanied with the 

 remains of mammalia, such as the mam- 

 moth, etc., which are now wholly or locally 

 extinct, while the mammalian remains found 

 with those of 7i€olithic man are of existing 

 species. Lastly, the paleolithic remains are 

 found in the deposits of sand and gravel we 

 have described as imbedded within the till, 

 while the neolithic remains are found only 

 in the upper drift. Thus in one and the 

 same way the existence of man is shown 

 to extend to inter-glacial, probably to pre- 

 glacial times, and the meaning of the ap- 

 parent gap in his history between the 

 paleolithic and neolithic ages is explained. 

 The paleolithic, or interglacial, perhaps pre- 



glacial man, was driven from the coun- 

 try, or destroyed by the change from a 

 mild to an arctic climate; and, when the 

 arctic conditions passed away for the last 

 time, his place was filled by the neolithic, 

 or post-glacial man, from more southern 

 latitudes. We have indicated in a neces- 

 sarily general manner the central idea of 

 Mr. Geikie's book ; it contains a great deal 

 of very interesting information of a sub- 

 ordinate character, which will amply repay 

 perusal 



My Visit to the Sun ; or, Critical Es- 

 says ON Physics, Metaphysics, and 

 Ethics. By Lawrence S. Benson, au- 

 thor of " Benson's Geometry." New 

 York : James S. Burnton. 8vo, 15Y pp. 

 Price, $1.50. 



If we were called upob to state the ob- 

 ject for which this book was written, we 

 should say that it was to display what the 

 author evidently fancies to be a very wide 

 and accurate knowledge of science. With 

 all the flourish and clatter of a Don Quixote 

 charging the windmill, he impinges the 

 mighty lance of querulousness against the 

 feeble form of gravitation, utterly annihilat- 

 ing that venerable body. The atomic theory 

 in chemistry, and the Fayian and Franklin- 

 ian theories in electricity share the same 

 fate, as do many kindred absurdities long 

 fostered by the ignorance of man. And, as 

 if those blows did not inflict punishment 

 enough on the physicists, they are utterly 

 crushed by the entirely new and astonishing 

 revelation that final causes are unknowable. 

 The present volume is on physics, and the 

 most appalling fact that it contains is the 

 announcement that it is to be followed by 

 similar volumes on metaphysics, ethics, etc. 



The Principles of Science : A Treatise on 

 Logic and Scientific Method. By Prof. 

 Jevons. Macmillan. Price, $5.00. 



We recently noticed this important and 

 valuable work, and we now again refer to 

 it simply to inform such of our readers as 

 may be interested, that the publishers have 

 issued a special American edition (in one 

 volume) at a reduced price, which will make 

 it more accessible to that large class of stu- 

 dents to whom it makes a serious difference 

 whether the price of a book is nine dollars 

 or five dollars. 



