232 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 20, 



is equally certain, whetlier or not we suppose the macMnery employed 

 in the distribution of this mass from the centre to be waves of trans- 

 lation. For the proposition that the labouring force expended in 

 the transit of this mass of materials must be equal to the force ex- 

 erted, and that this force must be exerted in such portions as, at every 

 step, to overcome the friction and tenacity of the masses of rock, 

 shingle, and other detritus moved, is equally true, whatever be the 

 machinery employed. As no gradual or minute action could move 

 the masses in question through a yard of space, no accumulation of 

 such action, through any amount of time, could distribute the 

 masses through the great distances which the northern drift has 

 traversed, and spread them over the vast spaces which that formation 

 occupies. The distribution of the northern drift belongs to a period 

 when other causes operated than those which are now in action. 



Postscript. 



Perhaps it may throw some light upon the subject to remark that 

 a wave of translation diifers little from a " debacle " according to the 

 notions of earlier speculators. A wave of translation is a debacle 

 conceived according to the more exact notions to which modern science 

 has led. Or rather, since a debacle was generally conceived as a 

 vast torrent sweeping over the land, arising from the emergence of 

 a submarine area, or some such cause, we may say that a wave of trans- 

 lation, in such cases as we have considered, is a debacle travelling 

 along the sea after it has been shot off the land. 



2. A notice of a new Clinometer, presented to the Society by R. 

 Grantham, Esq., was then read ; for which he received the thanks 

 of the Society, and the Instrument was ordered to be deposited in 

 the Museum. 



3. On the Slow Transmission of Heat through loosely coherent Clay 

 and Sand. By James Nasmyth, Esq. Communicated in a letter 

 to Leonard Horner, Esq., P.G.S. 



"When I lately had the pleasure to see you at the foundry, on draw- 

 ing your attention to what appeared to me a remarkable example 

 of the low capability of mineral substances for conducting heat, I 

 was much gratified to find that you agreed with me in considering 

 that the instance in question had an important bearing on several 

 interesting geological questions, especially those relating to the theory 

 of the central heat of the earth. 



At your request I have much pleasure in sending you a statement 

 of the instance in question, under the impression that it may chance 

 to prove of some interest as an illustration of what may yet exist in 

 respect to the state of the interior of the globe, as regards its high 

 temperature. 



