Searles V. Wood—The Cause of the Glacial Period. 301 
those parts of Britain where the land-ice which glaciated our island 
was engendered is larger than that over the glaciated area of Hastern 
North America. 
As regards the isolated ice of the mountain regions of the world 
which underwent a great extension, and to explain which an increase 
of precipitation has been similarly assumed, the question presents 
itself whether this extension could not have taken place by an in- 
crease of the cold, though with a diminished precipitation. I can 
see no reason why it would not. So long as the snowfall on the 
mountains is more than the sun can melt in the year, the excess, 
whether great or small, must go on accumulating until the onward 
movement of the resulting ice-mass becomes balanced, and the lower 
limit of the mass defined by the wasting power of either the at- 
mosphere or sea; and as by the lowering of the sun’s heat during 
the Glacial period this excess of unmelted snow increased, notwith- 
standing that the actual snowfall may have diminished, the glaciers 
of the mountains increased in thickness as well as advanced. It was, 
I think, to the long duration of the major glaciation that the magnitude 
of the land-ice of that glaciation was due; for though I can see no 
indication of the cold of the minor glaciation in England having 
been less, the evidence which the land ice of this glaciation has left! 
indicates that the volume of this ice was very much less than was 
that of the major glaciation here. 
The advocates of the dynamical theory of the sun’s heat, finding 
their hypothesis inconsistent with the great lapse of time involved 
in the slow and gradual evolution of organic life, have called upon 
Geologists and Evolutionists to “hurry up their phenomena”; but 
the view that the sun’s heat is maintained by chemical action upon 
material diffused through the medium, in which are moving the sun 
and all the other members which make up the sidereal agglomeration 
of which the Milky Way affords a longitudinal view, involves no 
such inconsistency. Thus while on the one hand the chemical 
theory does not clash, as the dynamical does, with the reasonable 
inferences to which the study of Geological and Biological phenomena 
have led us, it is on the other, the only one which is consistent with 
the conclusion to which it seems to me all the phenomena of the 
Newer Pliocene period point, viz. a variation during that period in 
the heat emitted by the sun; for it is reasonable to suppose that the 
material thus diffused may vary in different parts of space, and the 
chemical action vary in its intensity accordingly. The many instances 
which have of late years been observed of coruscations or changes in 
the brilliancy of several stars (as distinguished from the periodical 
changes of many, such as Algol), and the short duration of some of 
these changes, strengthen the chemical theory. That theory has 
had the support of more than one chemist of reputation,’ though they 
1 See pp. 714 and 716 of my Newer Pliocene Memoir, in Q. J. G. 8. vol. xxxviii. 
2 It seems to have originated with Grove 40 years ago, and been recurred to by 
him in his Address as President of the British Assoc. in 1866. It has been made the 
subject of an aaa by W. Mattieu Williams on “The Fuel of the Sun,” and in 
a 
another form was last year advanced by C. W. Siemens. Sterry Hunt has also 
supported it. 
