JE. P. Ciiiverwell — Theory of the Ice Age. 3 



transverse bones, so that those bones extend between the rami of 

 the mandible. Notwithstanding the extremely heavy build of the 

 animal, there is much that recalls mammals in the characters of the 

 pelvis, the shoulder-girdle, and the fore and hind limbs; so that 

 the fossil stands alone at present in its approximation in these 

 regions of the skeleton to the highest vertebrata, though it is the 

 shoulder-girdle chiefly which fixes its affinity with the Monotremata. 

 The new knowledge of the reptilian skeleton which this animal 

 supplies gives a meaning to the term Ordinal Anomodontia, by 

 showing resemblances in the teeth to various groups of animals 

 which could never have been suspected from the reptilian structure 

 of the skull, or the mammalian structure of the extremities. 



It has been a pleasure to contribute a fossil which has made 

 this animal type more intelligible ; but it is no less a pleasure to 

 acknowledge that everything has been done by Dr. Henry Woodward 

 to secure that the specimen should receive the best treatment 

 possible, both before and after it was presented to the National 

 Collection. 



II.— A Criticism of the Asteonomioal Theory of the Ice Age, 

 AND OF Lord Kelvin's Suggestions in connection with a 

 Genial Age at the Pole. 

 By Edward P. Culvehwell, M.A., Fellow of Trinity College, Dublin. 

 (Part I.) 



WHILE the favourable reception which the Astronomical Theory 

 of the Ice Age has met with among scientific men has been 

 chiefly due to the writings of Dr. Croll, its more general acceptance, 

 especially among the semi-scientific public, has been greatly assisted 

 by the lucid and. vigorous exposition by Sir Eobert Ball, in his 

 " Cause of an Ice Age," published in 1891. But notwithstanding 

 the apparently exhaustive way in which Croll discusses the problem, 

 and the fact that Sir Robert Ball's work has been published in the 

 " Modern Science " Series (indicating that the theory has secured 

 a place among the permanent acquisitions of science), I venture to 

 think 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. The following pages contain what I hope will 

 be admitted to be a justification of this sweeping condemnation. 

 The first portion of my paper deals with Croll's form of the theory ; 

 the second, to be published next month, deals with Sir Eobert Ball's 

 form. 



Fart I. Examination of Croll's "Climate and Time." 

 Of the 527 pages of which the body of this work consists, only 

 a few are occupied with the direct eff"ects of the theory, somewhat 

 more with the indirect effects, over 150 pages with the theory of 

 oceanic circulation, upwards of 200 pages with the geological record, 

 the age of the sun, and glacier motion. Practically, the exposition 

 of the theory is contained in the four following chapters : — 



