s affecting the
surface features of the Earth are accompanied by one entitled _The
Abundance of Life._ This originated amidst the overwhelming
presentation of life which confronts us in the Swiss Alps. The
subject is sufficiently inspiring. Can no fundamental reason be
given for the urgency and aggressiveness of life? Vitality is an
ever-extending phenomenon. It is plain that the great principles
which have been enunciated in explanation of the origin of
species do not really touch the problem. In the essay--which is an
early one (1890)--the explanation of the whole great matter is
sought--and as I believe found--in the attitude of the organism
towards energy external to it; an attitude which results in its
evasion of the retardative and dissipatory effects which prevail
in lifeless dynamic systems of all kinds.

_Other Minds than Ours_? attempts a solution of the vexed question
of the origin of the Martian "canals." The essay is an abridgment
of two popular lectures on the subject. I had previously written
an account of my views which carried the enquiry as far as it was
in

xiii

my power to go. This paper appeared in the "Transactions of the
Royal Dublin Society, 1897." The theory put forward is a purely
physical one, and, if justified, the view that intelligent beings
exist in Mars derives no support from his visible surface
features; but is, in fact, confronted with fresh difficulties.

_Pleochroic Haloes_ is a popular exposition of an inconspicuous but
very beautiful phenomenon of the rocks. Minute darkened spheres--a
microscopic detail--appear everywhere in certain of the rock
minerals. What are they? The discoveries of recent radioactive
research--chiefly due to Rutherford--give the answer. The
measurements applied to the little objects render the explanation
beyond question. They turn out to be a quite extraordinary record
of radioactive energy; a record accumulated since remote
geological times, and assuring us, indirectly, of the stability
of the chemical elements in general since the beginning of the
world. This assurance is, without proof, often assumed in our
views on the geological history of the Globe.

Skating is a discourse, with a recent addition supporting the
original thesis. It is an illustration of a common experience--the
explanation of an unimportant action involving principles the
most influential considered as a part of Nature's resources.

The address on _The Latent Image_ deals wit