TRANSACTIONS OF THE SECTIONS. 57 



condition of the earth's crust, as infeiTed not only from the hypothesis of its con- 

 solidation from a fused nucleus, but from the acc-uniulated facts of recent inquiries 

 into the chemical and physical structure of rocks. The former condition of the 

 solid shell should have been highly fa\ourable to interchanges of heat between 

 the earth's watery coating and its interior, while chemical geology seems to estab- 

 lish that multitudes of mineral products, previously supposed to be the results of 

 dry fusion and solidification, have been really formed under conditions where both 

 heat and water were abundantly present. Metamorphic actions especially, as 

 alluded to by Sir Charles Lyell, have been sho-uTi to have been produced on a 

 vast scale by the infiltration of water. The influence which water may have thus 

 exercised as a heat-carrier is declared by Professor Hennessy to have been so 

 great, that the effects of conduction through the crust considered as a dry solid 

 may be regarded as comparatively insignificant. The author fm-ther considers 

 how his views regarding h3'drothermal action in the earth's crust would accelerate 

 the cooling of the supposed interior source of heat, and he comes to the conclusion 

 that this would take place much more rapidly than we have been hitherto led to 

 believe from the calculations of mathematicians who considered only the unreal 

 case of a dry continuous solid. He also points out that lij'drothermal action, 

 imlike mere conduction, might be intermittent in its energy, while the efforts of 

 the latter must diminish continuously. 



The remainder of the paper is occupied with a discussion of the relative in- 

 fluences of air, earth, and water on the reception, retention, and distribution of 

 heat coming from exterior and interior sources. The author adduces further proofs 

 of the conclusions to which he was led in his essay on the influence of the distri- 

 bution of land and water on terrestrial temperature during different geological 

 epochs, of which an outHne had been communicated to the dissociation in 1856, 

 although the paper itself did not appear in a complete fonn until three years sub- 

 sequently*. One of these conclusions was subsequently adopted by Professor 

 Phillips, and this is now further extended by the autbor. It appears to him that 

 the distribution of land and water most favourable, upon the whole, to a general 

 augmentation of terrestrial temperature arising from all possible primary sources, 

 is that of a water-covered spheroid, with numerous small islands scattered over its 

 surface. The physical conditions originatino- a low temperature are also examined, 

 and finally the circumstances most favourable to the presence, at the same epoch 

 of time, of opposite, contiguous, and simultaneous chmatic conditions. Among 

 other questions, the influence of diy and moist thei-mal currents of air upon snow 

 and ice was discussed from considerations depending on the capacity of air and 

 vapour for heat. From these considerations it follows that, while cold moist air 

 favours the formation of snow and glaciers, warm moist air is highly favourable to 

 their destruction compared with dry air at the same temperatiu'e. 



The author has thus been led to adopt views as to the possible formation and 

 development of glaciers at former epochs apparently in harmony with some of the 

 conclusions of Charpentier, Tyndall, and Franklan'd. It seems to foUow from the 

 views developed by the author that epoclis characterized by the simultaneous co- 

 existence of very different climatic conditions over diflerent regions would depend 

 upon variations in the distribution of land and water, combined with obstructions 

 of the hydrothermal agency, whereby the surface of the earth receives heat froiu 

 its interior. Geological observation seems to point out that such conditions woulil 

 be most likely to arise during the later and prehistoric formations, as well as durinu- 

 the period of the physical history of the planet which now witnesses the develoj - 

 ment of oiu" own race. 



Note on some of the Oolitic Strata seen at Dimdry. By M. H^beet. 



On Otolites. By E. S. HioGiifS. 



On the Oricjin of certain Eocls, and on the Ossiferous Caverns of the South of 

 Bevonshire. By H. C. Hodge. 



* See Atlantis, January 1859 ; and Pliil. Mag. vol. xvii. 8. 4. p. 181. 



