umably of liquid water,
from Mars. It is true that the spectroscopic argument is purely
negative, and this may be due to the extreme delicacy of the
observations required; but that dependent on the inability of the force
of gravity to retain it is positive scientific evidence against its
presence, and, till shown to be erroneous, must be held to be
conclusive.

This absence of water is of itself conclusive against the existence of
animal life, unless we enter the regions of pure conjecture as to the
possibility of some other liquid being able to take its place, and that
liquid being as omnipresent there as water is here. Mr. Lowell however
never takes this ground, but bases his whole theory on the fundamental
identity of the substance of the bodies of living organisms wherever
they may exist in the solar system. In the next two chapters I shall
discuss an equally essential condition, that of temperature, which
affords a still more conclusive and even crushing argument against the
suitability of Mars for the existence of organic life.

CHAPTER V.

THE TEMPERATURE OF MARS--MR. LOWELL'S ESTIMATE.

We have now to consider a still more important and fundamental question,
and one which Mr. Lowell does not grapple with in this volume, the
actual temperatures on Mars due to its distance from the sun and the
atmospheric conditions on which he himself lays so much stress. If I am
not greatly mistaken we shall arrive at conclusions on this subject
which are absolutely fatal to the conception of any high form of organic
life being possible on this planet.

_The Problem of Terrestrial Temperatures._

In order that the problem may be understood and its importance
appreciated, it is necessary to explain the now generally accepted
principles as to the causes which determine the temperatures on our
earth, and, presumably, on all other planets whose conditions are not
wholly unlike ours. The fact of the internal heat of the earth which
becomes very perceptible even at the moderate depths reached in mines
and deep borings, and in the deepest mines becomes a positive
inconvenience, leads many people to suppose that the surface-
temperatures of the earth are partly due to this cause. But it is now
generally admitted that this is not the case, the reason being that all
rocks and soils, in their natural compacted state, are exceedingly bad
conductors of heat.

A striking illustration of this is the fact, that a stream of lava o