THE PRINCIPLES OF BIOLOGY. 
45 
this seems an insufficient cause to account for the circum¬ 
stance, and the theory described above offers a very simple 
and sufficient explanation. In the daily contraction of a 
glacier, the small strength of cohesion of the ice, and the very 
great friction of the bed, will not only absolutely prevent the 
whole glacier being pulled back as one mass, but will 
necessarily result in its being pulled asunder transversely, 
and pulled to pieces, thus forming the transverse crevasses. 
Another important point that has to be referred to is the 
scoring and grooving in longitudinal lines that takes place in 
the bed of glaciers, and that has left such remarkable records 
of the ancient glaciers of the “ Great Ice Age.” These are 
great scratches, amounting in many cases to definite grooves, 
that have been formed by the scraping along of hard stones 
under the enormous pressure of the great mass of glacier; 
but when the amount of force is considered that must have 
been employed in ploughing out such grooves in hard rock, it 
is seen that this cannot have been effected by the simple 
passage over it, once for all, of a stone embedded in the ice. 
If, however, the glacier descended by a long-continued series 
of oscillations, according to the theory here named, so that 
the stone passed a great many times over the same spot, 
backwards and forwards, the result becomes intelligible. 
The above-named theory of glacier motion, which 
originated with Canon Moseley, was further developed after 
his death by the late Mr. Walter Browne, from whom I 
obtained most of the information given in this paper. 
THE PRINCIPLES OF BIOLOGY.* 
BY HERBERT SPENCER. 
Exposition of Part IV., Chapters XII. and XIV. 
BY F. J. CULLIS, F.G.S. 
To the evolutionist all things are as they are, simply 
because the natural forces to which they are and have been 
subject have been and are, such as could produce just this 
and no other result. 
Mr. Spencer, in the fourth part of his Biology, shows this 
to be true of organic forms, and those of his pages in which 
lie applies the doctrine to the morphology of plants have been 
* Birmingham Natural History and Microscopical Society, Socio¬ 
logical Section, March 18th, 1886. 
