. 
E nit 
J. R. Mayer on Celestial Dynamics, 411 
earth, wash away, so to speak, a portion of the heat, and thus 
accelerate the cooling of the globe. The whole quantity of 
nos. As the heat which accompanies the molten matter to the 
surface is derived from the store in the interior of the earth, 
their action must influence considerably the diminution of the 
earth’s heat. And we not only to consider here actual 
eruptions which take place in succession or simultaneously at 
different parts of the earth’s surface, but also volcanos in a qui- 
escent state, which continually radiate large quantities of heat 
abstracted from the interior of the globe. If we compare the 
posed, and thus opening a door for the escape of heat, 
Of the whole of the heat which passes away through these 
numerous outlets, too low an estimate must not be made. To 
have some basis for the estimation of this loss, we have to re- 
collect that in 1783, Skaptar-Jokul, a voleano in Iceland, emitted 
sufficient lava in the space of six weeks to cover 60 square miles 
of country to an average depth of 200 metres, or, in other 
words, about 14 cubic’ mile of lava. The amount of heat lost 
by this one eruption of one volcano must, when the bigh tem- 
perature of the lava is considered, be estimated to be more than 
1000 cubic miles of heat; and the whole loss resulting from the 
to thousands of cubic miles of heat per annum. This latter 
number, when added to Fourier’s result, produces a sum which 
evidently does not agree with the assumption that the volume of 
our earth has remained unchanged. 
In the investigation of the cooling of our globe, the influence 
of the water of the ocean has to be taken into acount. Fourier’s 
calcultions are based on the observations of the increase of the 
temperature of the crust of our earth, from the surface toward 
the centre. But two-thirds of the surface of our globe are cov- 
ered with water, and we cannot assume @ priori that this large 
area loses heat at the same rate as the solid parts; on the con- 
trary, various circumstances indicate that the cooling of our 
globe proceeds more quickly through the waters of the ocean 
resting on it than from the solid parts merely in contact with the 
LIT} ere. ‘ 
dies first place, we have to remark that the bottom of the 
