M. de Beaumont on the Glacier Theory. 113 



faction produced at the inferior portion of the whole snowy 

 surface. 



Any diminution in the influx of internal heat would also 

 have the effect, in the course of time, of giving rise to glaciers 

 at points where they do not exist at the present day ; and 

 this is what must take place in remote futurity when the cen- 

 tral heat shall have suffered a sensible diminution. 



In former times, on the contrary, the flow of heat must 

 have been greater than at present, and this cause must have 

 tended to render glaciers a little shorter ; if they were more 

 extensive at a certain epoch, as every thing seems to indicate, 

 such an extension must have resulted from differences between 

 the climate of former periods and that of the present day.* 



2(1 Ixemark ; relative to the injiuence of external cold on the for- 

 mation of glaciers. — Certain expressions, pci'haps misinter- 

 preted, have been the cause of there being attributed to some 

 of the individuals who are at present occupied with the theory 

 of glaciers, the opinion that the water, formed at their sur- 

 face during the day, and introduced into the capillary fissures, 

 congeals there during the night by the penetration of the noc- 

 turnal cold ; but M. de Charpentier, at the end of the interest- 

 ing woi"k he has published, Sur les glaciers et sur le terrain 

 erratique dubassin du Bhone, rejects this idea Q). 307), and 

 even terms it absurd. In fact, the conductibility of ice, which 

 indeed has not yet been measured, cannot be very much 

 greater than that of the rocks forming the surface of the 

 ground. It is therefore evident, that the nocturnal cold can 

 only congeal the water in the interior of a glacier to an incon- 

 siderable depth, such as that to which the diurnal variations 

 of temperature penetrate into the ground with a sensible in- 

 tensity. 



But then, how can the water become congealed in the in- 

 terior of glaciers, as is supposed by the theory which regards 

 their progression as an effect of dilatation ? This congelation 

 cannot take place without a considerable abstraction of heat, 



* I have elsewhere suggested the supposition as to this point, which ap- 

 peax-s to me the most probable. (See Annales des Sciences Gcologigues. vol . 

 i., p. 20-1, and Comptes Rcndtis de I' Acadcmie de Sciences, vol. xiv., p. 101.) 



VOL. XXXIV. NO. LXVII. .TAXUARY 1843. II 



