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Remarks on two Points in the Theory of Glaciers. By M. 

 Elie de Beaumont, Member of the Royal Academy of 

 Sciences.* 



The lectures which I delivereil this year at the College de 

 France on erratic phenomena, led me to examine the theory 

 of glaciers, and I now ask the permission of the Society to 

 submit to their attention two theoretical remarks which have 

 occurred to me in the course of my investigations. 



\st Remark ; relative to the action which central heat exercises 

 on glaciers. 



The increase of temperature observed in penetrating the 

 solid crust of the earth, gives rise to a constant flow of 

 heat which traverses that crust, and is dissipated at its sur- 

 face. If we call ^ the fraction of a degree by which the tem- 

 perature becomes augmented when we penetrate to the depth 

 of a metre, and k the conductibility of the terrestrial crust, 

 this flow of heat has as its measure the product ff. k. This 

 flow of heat would be capable of melting, taking time as 



unity, a bed of ice whose thickness would be ^ . I attempted, 



some years ago, to calculate approximately this quantity 

 for the surface of the ground at the Observatory of Paris, 

 and I found that the flow of heat which proceeds from the 

 earth, would at that locality melt annually a bed of ice of 

 0"i- 0065 (six millimetres and a half), a result which M. Pois- 

 son has inserted in his work, entitled, Memoire et notes for- 

 viant mi supplement a la theorie mathematique de la chaleur 

 (Paris 1837.) This quantity may doubtless vary from one 

 point on the surface of the globe to another with the values 

 of k and ^; but it seems to me very probable that the varia- 

 tions would not be extensive, and that by admitting that the 

 flow of heat emanating from the terrestrial crust, and dis- 

 sipated at the surface, is generally capable of melting 6 mil- 

 limetres and a half of ice in the year, and of producing, by 



* Road to the Philoinatliic Society of Paris, 30th July 1842. A corrected 

 copy of this paper, and the following one, was kindly ti-aiismitted to us by the 

 Authoi-.— Ed. 



