74 Reviews — Dr. CroU's Life and Work. 



Whether right or wrong, the Astronomical Theory of Geological 

 Climate, which found in Croll its most original advocate, has met 

 with no small degree of acceptance in the world of science. Thus, 

 imder the article " Geology " in the Encyclopcedia Britannica, Croll 

 contributed an outline of the "Secular Theory of the Change of 

 Geological Climate" ; whilst a full abstract of his views on Climate 

 in its Geological relations, drawn up by himself, was admitted into 

 Sir Archibald Geikie's "Textbook of Geology" (1882, p. 23 

 et seq.). More recently somewhat similar views have been ex- 

 pressed by Sir Eobert Ball in his "Cause of an Ice Age," which 

 appeared in 1891, and has since been published in the "Modern 

 Science " Series, thus indicating by implication the general acceptance 

 of the theory, now no longer regarded as a mere hypothesis. 



Nevertheless, from time to time, critics have arisen who ventured, 

 in a greater or less degree, to contest the methods by which these 

 conclusions have been reached. It will suffice to instance two from 

 our own pages. The Eev. E. Hill, in an article on " Eccentricity 

 and Glacial Epochs" (Geological Magazine, February, 1880), 

 prefaces his criticisms by the admission that " Climate and Time " 

 was perhaps the most important geological work that had recently 

 appeared ; " certainly," he says, " the most valuable and original 

 that refers to Glacial Geology. It teems with novel and instructive 

 ideas." Then comes the criticism, summed up as follows : — " We 

 have thus gone thi'ough Dr. CroU's four causes, or rather modes of 

 action, whereby high eccentricity might, as he maintains, produce 

 a Glacial period. The first is non-existent. The second may 

 possibly have an effect. The third at best cannot work at all, and 

 almost certainly works in the wrong direction. The fourth 

 [deflection of ocean currents owing to intenser trade-winds] might 

 work if set agoing, but has no power of starting itself?" Mr. Hill's 

 verdict, thei-efore, was one of " Not Proven," though he considered 

 that Croll had attacked the problem in a right manner; and he 

 seemed inclined to believe, with Croll, that variations in eccentricity 

 did bring about the Glacial period. 



More recently the Astronomical Theory of the Ice Age, as 

 enunciated by Croll, and subsequently (1891) by Sir Eobert Ball, 

 has been criticized by Mr. E. P. Culverwell, Fellow of Trinity 

 College, Dublin, in the Geological Magazine (January and 

 February, 1895). This author considei-ed himself justified in 

 stating " that a careful examination of the problem will show that 

 the theory is but a vague speculation ; clothed, indeed, with 

 a delusive semblance of severe numerical accuracy, but having no 

 foundation in physical fact, and built up of parts which do not 

 dovetail one into the other." It is far mathematicians and physicists 

 to decide between these contending authorities. But we may, at 

 least, call attention to Seebohm's desci-iption of the advent of 

 summer in Siberia, as quoted by Mr. Culverwell ; who complains 

 that CroU's illustrations of the effect of summer heat are all selected 

 from regions where the sun-heat has to contend, not only with 

 the ice or snow actually on the ground, but also with the cold 



