288 The Age of this Earth. [May, 
chief authorities, for physical considerations render it impossible 
that more than 10,000,000 or 15,000,000 of years can be granted.” 
Before entering on physical details it will be as well to point out 
a curious question between mathematicians and geologists in ref- 
erence to “ under-ground temperature.” Some geologists assign 
all igneous action on this earth to local chemical causes ; but the 
fashionable school allows its ignorance on this subject in the 
Text-Book of Geology, by Mr. Page, seventh edition, page 51: 
“ The occurrence of volcanoes, earthquakes, escapes of heated 
vapors, and thermal springs are by far too numerous and gen- 
eral to be accounted for on any principle of chemical union with 
which we are acquainted.” In other words, the expenditure of 
heat from the earth is supposed to be more than local chemical 
causes could supply. Mathematicians give * 20,250,000” years 
of heat to the sun; as this earth is supposed to have been an off- 
shoot from its “ fiery mass,” we may infer that when the earth 
was detached it must have been in the same hot condition as 
the parent mass. Mr. Proctor gives us the diameter of the sun 
at 850,000 miles, and Guyot’s geography gives the diameter of 
this earth at eight thousand miles. If, then, the diameter of the 
sun contains heat for 20,250,000 years, the diameter of this 
earth can hold heat only for 190,588 years. We know nothing 
of fresh supplies of fuel to earth or sun, in reference to the the- 
ory of Laplace; we give the sun the credit for greater expendi- 
ture of heat than the earth; but if geologists are right in suppos- 
ing that local chemical causes have been unequal to the earth’s 
expenditure, and that this has been going on for ten, twelve, 
fifty, or one hundred millions of years, according to the calcula- 
tions of physical science, we may wonder why the internal fire 
did not become bankrupt long ago. We may also remark, in 
passing, that if igneous action is of any advantage to this earth, 
it is lucky that neither science had any hand in its origin. 
It was pointed out by the German metaphysician, Kant, and 
' has been accepted by others, that there has been a retardation 
of the earth’s revolution from the tidal wave. The conclusion, 
as given in the Quarterly, is, “She was rotating at about the 
same rapidity as now when she became solid, and as the rate 0 
rotation is certainly diminishing, the epoch of consolidation can- 
not be more than ten or twelve millions of years.” This calcula- 
tion cannot be of much consequence to the cosmical system ; bat 
as no one knows how the tidal wave acted before there was lan 
for it to flow and ebb upon, we put the theory down as useless, 
