The composition of a nebula as disclosed to us by these researches is very instructive. Here we are looking at an object which seems to lie at the very limits of the visible universe—an object so remote that our attempts to fathom its distance are quite unsuccessful; yet in this inconceivably distant part of our system we find at least one ingredient which we know well on the earth. Previous to actual trial no one would have expected, I think, to find the Great Nebula largely constituted from such a familiar element as hydrogen. This gas enters into the composition of water, and is thus an element of extreme abundance on the earth. That an element so common with us here should also be abundant in these awfully distant regions of the universe is one of the most astonishing facts that modern science has revealed. As the eye follows these ramifications of the Great Nebula, ever fading away in brightness until it dissolves in the blackness of the sky; as we look at the multitudes of bright stars which sparkle out from the depths of the great glowing gas; as we ponder on the marvelous outlines of a portion of the nebula, we are tempted to ask what the true magnitude of this object must really be. Here, again, we have to confess that science is unable to satisfy this very legitimate curiosity. The only means of learning the true length and breadth of a celestial object depends upon our first having discovered the distance from us at which the object is situated. Unhappily we are, as I have said, entirely ignorant of what this distance may be in the case of the Great Nebula in Orion. Our ordinary methods of conducting such an inquiry are hardly applicable to such an object, and its position so near the Equator introduces fresh difficulties into the problem. We shall, however, certainly not err on the side of exaggeration if we assert that the Great Nebula must be many millions of times larger than that group of bodies which we call the Solar System. COLORED, DOUBLE, MULTIPLE, BINARY, VARIABLE AND TEMPORARY STARS. —J. E. GORE