July, 1895. SOME NEW BOOKS. 77 



Prestwich tells us that " there is every reason to believe . . . 

 that Palaeolithic Man and his companions came down to within some 

 10,000 to 12,000 years of our times " (p. 11), we regard his estimate 

 as quite as unphilosophical as those, seven times as long, against 

 which he argues. The second article attempts to estimate the date 

 and duration of the Glacial Period ; it seems open to the same objec- 

 tion, that the data are too inexact to repay the labour of using. The 

 third article appears to us the most important in the volume, as it 

 contains more new matter than the others, and is illustrated by a 

 series of good plates. It describes the evidence for the supposed 

 existence of man on the chalk plateaux of Kent in times earlier than 

 the Palaeolithic, and coincident or earlier than the gravels known as 

 the " Southern drift." The implements are of a very primitive 

 character, and many competent authorities have declined to accept 

 them as of human workmanship. The specimens figured on the 

 plates, however, seem convincing. There are, however, with these 

 some of the normal Palaeolithic implements, such as a spear head of 

 the St. Acheul type (pi. xi.. Fig. 38) ; and how the two series came 

 into association. Professor Prestwich admits to be still uncertain. 



The fourth article discusses the various theories that have been 

 put forward to account for the water given off in volcanic eruptions. 

 Professor Prestwich maintains that the old theory, that volcanic 

 action is one of the results of contraction of the earth during cooling, 

 is in fullest agreement with the facts, and further, that the steam 

 given off is formed from water which works its way down from the 

 surface, and is not occluded by the rocks of the interior. The article on 

 the " Thickness and Mobility of the Earth's Crust " is that which is most 

 likely to arouse energetic dissent, especially from its conclusion that 

 volcanic action is incompatible with a thick crust. The final article 

 discusses at length the data by which the rate of increase of under- 

 ground temperatures can be determined. The numerous probable 

 sources of error are described, and many of the most familiar measure- 

 ments are dismissed for failure to allow for these. Professor Prest- 

 wich rejects a large number of records, and from those which he 

 accepts he calculates the mean rate of increase of temperature as 

 I degree Fahr. for every 48 feet. 



J. W. G. 



In our review of the four-handed text-book on Botany recently issued 

 by Gustav Fischer, we asked how it was possible to issue so admir- 

 able and so copiously illustrated a work at so small a cost. The 

 publisher writes to inform us that the cost of publication is not 

 appreciably less in Germany than in England, less still has Bonn 

 University anything to do with the matter. The explanation, he 

 says, is due to the great pleasure he has had in bringing out as 

 cheaply as possible a book which the four Bonn professors and 

 teachers had done their best to make as valuable and original as 

 possible. 



Messrs. Dulau & Co., who have been appointed agents for the sale 

 and distribution of the Royal Society's publications, have issued a 

 complete price list of those that are still to be had. 



