can be seen more frequently and studied more satisfactorily on a photographic plate.  These granules have an obvious resemblance to clouds; and clouds, indeed, we may call them.  There is, however, a very wide difference between the solar clouds and those clouds which float in our own atmosphere.  The clouds which we know so well are, of course, merely vast collections of globules of water suspended in the air.  No doubt the mighty solar clouds do also consist of incalculable myriads of globules of some particular substance floating in the solar atmosphere.  The material of which these solar clouds are composed is, however, I need hardly say, not water, nor is it anything in the remotest degree resembling water.  Some years ago any attempt to ascertain the particular substance out of which the solar clouds were formed would at once have been regarded as futile; inasmuch as such a problem would then have been thought to lie outside the possibilities of human knowledge.  The advance of discovery has, however, shed a flood of light on the subject, and has revealed the nature of that material to whose presence we are indebted for the solar beneficence.  The detection of the particular element to which all living creatures are so much indebted is due to that distinguished physicist, Dr. G. Johnstone Stoney.

In the whole range of science, one of the most remarkable discoveries ever made is that which has taught us that the elementary bodies of which the sun and the stars are constructed are essentially the same as those of which the earth has been built.  This discovery was indeed as unexpected as it is interesting.  Could we ever have anticipated that a body ninety-three millions of miles away, as the sun is, or a hundred million of millions of miles distant, as a star may be, should actually prove to have been formed from the same materials as those which compose this earth of ours and all which it contains, whether animate or inanimate?  Yet such is indeed the fact.  We are thus, in a measure, prepared to find that the material which forms the great solar clouds may turn out to be a substance not quite unknown to the terrestrial chemist.  Nay, further, its very abundance in the sun might seem to suggest that this particular material might perhaps prove to be one which was very abundant on the earth.

[Illustration:  THE SUN’S CORONA.

From a photograph taken by Professor Schaeberle, at Mina Bronces, Chili, in April, 1893, and kindly loaned by Professor E.S.  Holden, director of the Lick Observatory.]

I had occasion to make use of the word carbon in a lecture which I gave a short time ago, and I thought when I did so that I was of course merely using a term with whose meaning all my audience must be well acquainted.  But I found out afterwards that in this matter I had been mistaken.  I was told that my introduction of the word carbon had quite puzzled some of those who were listening to me.  I learned that a few of those who were unfamiliar with this