1877.] The Age of this Earth. 287 
Mathematicians are so correct in their figures that when they 
start from one point to reach one end, their ends ought to be the 
same; when these ends vary and we find no fault in the calcula- 
tion, we must look into the data for the cause of variation and 
error. 
The article alluded to gives us an outline of cosmical begin- 
nings from the theory of Laplace, published in 1796 (Maunder). 
Astronomers had been aware that many nebule floated in space ; 
these became ‘‘ specimens of worlds in making,” under the pow- 
erful telescope of the French astronomer. As the nebulæ became 
denser, they came under ‘the action of gravity ;” consequently 
‘ a succession of rings, concentric with and revolving round the 
centre of gravity,” were formed. ‘Each ring would break up 
into masses, which would be endued with motions of rotation, 
and would in consequence assume a spheroidal form. These 
masses formed the planets, and gathering with energy round its 
centre formed the sun.” It is then explained “ that the earth 
could not have had an independent existence till long after that 
time . . . for before then the earth must have formed part of 
the fiery mass of the sun;” the Quarterly observing, ‘ Thus, 
probably, was the world we live in and the solar system of which 
we form a part evolved out of chaos.” 
Science has proved that motion causes heat, and therefore the 
sun was provided with a supply by the action of the nebula. If 
they were cold when they came together, — the only condition they 
could have been in, —the supply of heat was calculated to last for 
20,250,000 years at the present rate of consumption. Thus “the 
dynamical theory of the sun’s heat renders it almost impossible 
that the earth’s surface has been illuminated by the sun’s rays 
many times ten millions of years; and when we consider under- 
ground temperature, we find ourselves driven to the conclusion 
that the existing state of things on the earth, life on the earth, 
and all geological history showing continuity of life must be 
limited within some such period of time as 100,000,000 years.” ’ 
This authority, Sir William Thomson, is reported to have told 
the British Association at Glasgow that ‘50,000,000 years is 
an even estimate ” for the age of this earth. i 
A comfortable thargin of fifty per cent. seems convenient to 
the precise sciences. Professor Tait is reported to have said in a 
Mie lecture at Glasgow, in alluding to differences on this subject, 
So much the worse for geology. as at present understood by its 
1 The Mail, September 8, 1876. : 
