232 Reviews — Prestwich's Controverted Questions in Geology. 



in a century taken from the coast of Norway, when at the North 

 Cape it is as much as five feet in a century. 



He refers to the vast antiquity of man, based on his contem- 

 poraneity with the extinct mammalia and the recurrence of Glacial 

 periods, but whilst he condemns the needless demands of glacialists 

 who fix the disappearance of Palcieolithic man and the Quaternary 

 fauna at 80,000 years back, he states that it is possible, on other 

 grounds, that the antiquity of man will have to be carried back 

 further into the Glacial period (see footnote, p. 8). 



Other estimates of time are based on the Westleton marine shingle- 

 bed, Bucks, at 600 feet above o.n., and the same bed in Suffolk 

 occurring at sea-level; on the Moel Tryfaen shell-bed at 1400 feet 

 elevation, estimated at 88,000 years ; and the raised beaches of 

 Norway 200 to 600 feet, assumed to be from 8000 to 24,000 years 

 old. From the Westleton bed he argues that the time-estimates, 

 based on the other raised beds, are worthless, in which we cordially 

 agree. 



Professor Prestwich then protests against those ph3'sicists who 

 maintain the theory of a rigid crust, and cites the modern raised 

 beaches, etc., as evidence in refutation of such a view. He also 

 doubts the assumption of a solid crust of 800 to 2500 miles in 

 thickness, and prefers to leave it an open question, and suggests that 

 it is probably not more than 20 to 30 miles thick. 



Article 2 is devoted to " Considerations on the date, duraticm, and 

 conditions of the Glacial Period, with reference to the Antiquity of 

 Man." Here the author makes use of the data regarding modern 

 glaciers and other evidence to show that the enormous periods of 

 time required by Croll's theory are uncalled for, and the evidence 

 for successive Glacial epochs unsatisfactory. 



Professor Prestwich's next essay is " On the primitive characters 

 of the Flint Implements of the Chalk-plateau of Kent, with reference 

 to the question of age and make." This article is illustrated by 

 twelve plates of worked flints, showing the various characteristic 

 forms that are relied upon by the author to establish the presence 

 of man antecedent to the time when these implementiferous flint- 

 gravels were formed, and long antecedent to that when the present 

 valley-system had been excavated. 



The fourth article, " On the Agency of Water in Volcanic Eruptions, 

 and on the primary cause of Volcanic Action " (illustrated b3' plate 

 xiii), is followed by one " On the thickness and mobility of the 

 Earth's Crust from the geological standpoint " ; the sixth and last 

 being "On Underground Temperatures — with observations on certain 

 causes which influence the conductivity of rocks ; on the thermal 

 eifects of saturation and imbibition ; and on a source of heat in 

 mountain-ranges, as affecting some underground temperatures." ^ 



^ It may interest some of our readers to know where these articles first appeared. 

 Art. 1 appeared in the "Nineteenth Century" for October, 1893, p. 551. Art. 2, 

 in the Quart. Journ. Geol. Soc. August, 1887, vol. xliii, p. 393. Art. 3, in the 

 " Journ. Anthrop. Inst." for 1892, p. 246. Art. 4, Proc. Eoy. Soc. April, 1885, 

 p. 117. Art. 5, ibid. April, 1888, p. 156. Art. 6, ibid. 1885, p. 1. 



