1862.] 173 



The fluviatile origin of the different gravels, as well as the greater 

 action of ice at the higher levels, is therefore confirmed, as is also the 

 suggestion that the volume of water carried down at the period in ques- 

 tion by the rivers was infinitely greater than it now is. At the same 

 time the view now given both explains the origin of the loess, so long 

 an unsettled problem, and harmonizes with the hypothesis before 

 advanced in explanation of the accompanying general phenomena. 



XIII. " On the Simultaneous Distribution of Heat throughout 

 superficial parts of the Earth." By Professor H. G. HEN- 

 NESSY, F.R.S. Received June 19, 1862. 



(Abstract.) 



The principal object of this memoir is to develope the laws of the 

 distribution of temperature in the portion of the atmosphere in con- 

 tact with the earth, and to point out the connexion between the phe- 

 nomena of aerial temperature and those of soil and oceanic tempera- 

 ture. The author maintains that hitherto no perfect physical repre- 

 sentation of the distribution of heat over the earth's surface has 

 been obtained. Hurnboldt's luminous method of representing the 

 distribution of mean temperatures necessarily presents us with the 

 temperatures of places at those hours of local, time when the tempe- 

 rature happens to be equal to that of the entire day. But such hours 

 occur at different places not at the same moment of absolute time, and 

 therefore the isothermal lines traced by the aid of their results alone, 

 are not true isothermal lines in the same sense as we understand 

 an isothermal line or surface within crystals, or other definite geo- 

 metrical solids which have been recently the subjects of thermological 

 inquiry. 



The distribution of sunshine at the outer limits of the atmosphere 

 and at its base is first considered, and the nearly circular shape of 

 the lines of equal sunshine is pointed out. After showing the con- 

 nexion between these lines and the simultaneous isothermals for the 

 air, land, and water, the author proceeds to more particularly discuss 

 the aero thermal lines. As the term isothermal line has become uni- 

 versal in the sense of a line joining places possessing the same mean 

 temperatures, the author proposes to designate the true lines of si- 



