160 
Proceedings of the Royal Physical Society. 
II. On the Geographical Distribution of the Marine Invertehrata in 
past time, considered in relation to the Doctrine of the Secular 
Cooling of the Earth. By Andrew Taylor, Esq. 
The doctrine of the secular cooling of the earth has again 
been prominently brought before the scientific public, by 
two ingenious calculations regarding the time required for 
such a phenomenon to take place. 
Professor Haughton of Dublin demands 1018 millions of 
years for the earth to cool down from 212° F. to 122° F. ; 
the latter temperature being supposed the one at which the 
waters became habitable. He moreover demands the farther 
period of 1280 millions of years for the cooling from 122° F. 
to 77° F. ; a period comprising the whole time from the first 
appearance of life in the earth to the latest Eocene epoch. 
If such decided physical changes have occurred during the 
period from the appearance of life on the globe to the daw^n 
of the present creation, they must have influenced very de- 
cidedly the succession and distribution of life in the geologic 
eras. 
If such calculations can be ranked amongst the ascer- 
tained facts of science, biological speculations founded on 
them will likewise pass from hypothetical probabilities into 
scientific deductions. 
That they are far from this, however, may be seen by 
alluding to Professor William Thomson's calculations on 
this subject : he fixes the time required for the whole period 
of the earth's crust from a state of fusion to its present 
condition, at 98 millions of years, and therefore allows only 
100 millions of years for all speculations regarding the 
earth in its solid state. Experimental data are adduced 
in support of his assertions. Such are the widely discre- 
pant results attained by two eminent savans. Do they not 
throw great uncertainty on the whole subject ? 
Notwithstanding, it may not be unphilosophical to inves- 
tigate the appearance and distribution of life in geologic 
times, on the assumption that this hypothesis is an ascer- 
tained physical fact. 
