for supplying energy, namely the breaking up of an atom, of which no suspicion had entered any one's head till recently. If, as we seem entitled to think, there is this kind of power-house available in the Sun, he need not be shrinking so rapidly—indeed he need not be shrinking at all. The calculations of Lord Kelvin are, in fact, rendered so much waste-paper, since they start with an assumption which may not be correct at all.
I am sure you would all like to see just one experiment with radium, as you have heard so much about it. We will charge up this electroscope so that the gold leaves stand apart from each other. If now I bring a little radium near it, they close together, showing that the electric charge has been removed, and yet you see I have not actually touched anything. The fact is that little particles are shooting out from the radium: they hit the gold leaves and carry off the electricity.
I must now come to the third reason for the Sun's great importance. The first is that he gives us light, heat and life in such profusion as led to its worship in old days. The second reason is that our Earth and the other planets are actually parts of the Sun, who must be regarded as our parent (as the Moon is our child), and the third reason is that he is the nearest star to us. The Sun is really a star: other stars are a very long way off; but the Sun is comparatively near. The actual distance is 93 millions of miles, and you may think that that is not very near; and indeed it would not be very near if we were to go by an express train. Suppose we travelled in a train at the rate of sixty