262 Proceedings of the Royal Physical Society. 
even yet geologists in general do not feel satisfied with the 
concession, 
It certainly requires that a geologist should feel that he can 
place considerable reliance upon the value of his own set of 
facts and inferences before he can venture to call in question 
the validity of the conclusions arrived at by men of undoubted 
eminence in their own subjects, such as Lord Kelvin and 
Professor Tait are. Nevertheless, geologists still shake their 
heads, and repeat with approval Professor Huxley’s well- 
known saying that “Mathematics may be compared to a 
mill of exquisite workmanship, which grinds you stuff of 
any degree of fineness ; but, nevertheless, what you get out 
depends upon what you put in; and as the finest mill in the 
world will not extract wheat-flour from peascods, so pages of 
formule will not get a definite result out of loose data.” In 
the following pages I shall confine my attention to the purely 
geological side of the question, leaving the physicists to take 
up the discussion and deal with it in the light of new faets 
and views. The results at which they will eventually arrive 
will not, I feel confident, prove so discordant with geological 
evidence as those to which reference has just been made. 
I propose in the following pages to pass in review certain 
changes which are known to have taken place in the past, 
beginning with the latest periods and working backward. I 
shall therefore commence with the Glacial Period. 
Time required for the Physical Changes that have taken 
place during the Tertiary Period.—One of the best regions 
in the British Islands for the study of the changes which 
have taken place since the commencement of the Tertiary 
Period is to be found in the Inner Hebrides. It is true that, 
in regard to the sequence of glacial events, these islands do 
not afford us evidence quite as satisfactory as do other regions 
to the east. This, I think, is probably owing to the fact that 
the influence of the complex conditions known as the “ Gulf 
Stream” (whether in the bodily transfer of warm water, or 
in the northward transfer of aqueous vapour, which, by its 
condensation into rain, warms the air—matters not in the 
present connection), was maintained close to the edge of 
the present 100-fathom line west of Europe all through the 
