PRESIDENTIAL ADDRESS. 11 
However, slow as the process of condensation is, it is not 
endless. In time all the meteoritic dust will be collected 
into stars or planets, and in time the law-of dissipation of 
energy will bring all these bodies to a uniform temperature. 
So. at last, the movements due to the original unequal dis- 
tribution of matter will cease, and the life of the universe 
will come to an end. We know of no process of rejuvenes- . 
cence by means of which dissipation of energy, and the force 
of gravitation, might be counteracted. Several attempts 
have been made to refute the theory of dissipation of energy. 
but all have failed. The ether, which pervades space, is 
the only part of the Universe which shows no sign of evolu- 
tion. It alone remains unchanged. 
A casual glance at the stars gives us the impression of im- 
mutability. We still speak of the fixed stars in much the 
same way as our forefathers used to speak of the everlasting 
hills. But we know that they are not fixed. We know 
that the nearer stars, including the sun itself, are in swift 
movement; and we infer that all are so. But we can see 
no connection between their movements. Single stars, or 
small groups of stars, are rushing through space in various 
directions, and we cannot detect any common centre of 
gravity which holds them in control. The stars have not 
yet attained the regularity of movement that gravitation 
must bring about in a very ancient system, and this idea of 
the comparative youth of the Universe is strengthened when 
we remember that large numbers of the primitive meteor- 
ites are still wandering in space uncondensed into stars. If 
it be true that the sun is one of the oldest stars in the Uni- 
verse, and if, as geologists think, the earth is not more than 
a hundred millions of years old, then it may very weil be 
that the creation of the cosmic dust out of which the stellar 
Universe has been formed, took place less than two hundred 
millions of years ago. But, although it may be possible 
to place a limit to the age of the Universe, we can fix no 
time for its duration. It is impossible to form an estimate 
of the hundreds of millions of years that will pass before the 
end approaches. Still, a time must come when all energy 
will be equilibrated ; and when, possibly, the visible Universe 
may resolve itself into invisible, motionless ether. 
In the Solar System we can study the development of a 
meteoritic swarm in greater detail. Here we find that the 
whole of the meteorites did not collect into a single mass. 
but that several planets, as well as the sun, were formed 
simultaneously. It has been shown by’ Professor G. H. 
Darwin that the effect of many collisions among a swarm 
of meteorites would be to gradually eliminate orbits of great 
