﻿Reviews — Seer's Primceval World of Switzerland. 



'9 



downwards, but have turned upwards also. The dear old Stigmaria, 

 without a Sigillaria stem, is growing in the water, as in the early days 

 of geological inquiry. 



In order to account for a Carboniferous fauna and flora in high 

 northern latitudes, Dr. Heer advocates the theory that at that time 

 the preponderant heat on the earth was not that of the sun. It is, 

 however, a generally-received doctrine among geologists and phj'sicists 

 at the present day, that the influence of the earth's internal heat had 

 ceased to affect the climate of the globe long before either its crust, 

 its waters, or its atmosphere had become sufficiently modified to 

 admit of their becoming the abodes of living organisms. Any appeal, 

 therefore, to the internal heat of the earth in explanation of abundant 

 animal and plant life in high Arctic regions, either in Palasozoic or 

 Neozoic times, must be deemed unsatisfactory at the present day ; and 

 the key to the solution of the problem must be sought either in a 

 change in the inclination of the earth's axis, an increase of the sun's 

 heat, or probably in a combination of these causes together with a 

 complete change in the relative distribution of land and sea in both 

 hemispheres. Prof. Heer seems to regard the absence of light 

 during the long Arctic winter as unimportant, provided the heat 

 was only maintained well above freezing-point. Even the insects 

 of the Coal Period he believes to have been chiefly nocturnal. But 

 there were many diurnal insects present in the Coal Period besides 

 the nocturnal Termites and Cock-roaches.^ 



The accompanying figure is (together with others), by the courtesy 

 of Mr. Heywood, reproduced from Prof. Heer's work. 



Fig. 1. 



Fig. 1. Blatta helvetica, Heer, Coal-measures, Erbignon. 

 a. Wing of the natural size. b. The entire insect (restored by Heer). 



' See Quart. Journ. Geol. Soc. 1876, vol. xxsii. pp. 60-64, pi. ix. ; and Geol. 

 Mag. 1876, Decade II. Vol. III. pp. 519-520. 



