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in the latter region were those of Professor Rees of Columbia University, New York, and of Professor Doolittle, first at Lehigh, and later at the Flower Observatory, near Philadelphia.

The variation which we have described was originally demonstrated by S. C. Chandler, of Cambridge, in 1890 by means of a great mass of astronomical observations not made for this special purpose. Since then investigation has been going on with the view of determining the exact curve described. What has been shown thus far is that the variation is much wider some years than others, being quite considerable in 1891, and very small in 1894. It appears that in the course of seven years there will be one in which the pole describes the greater part of a comparatively wide circle, while three or four years later it will for several months scarcely move from its central position.

If the earth were composed of a fluid, or even of a substance which would bend no more than the hardest steel, such a motion of the axis as this would be impossible. Our globe must therefore, in the general average, be more rigid than steel.

The atmosphere is astronomically, as well as physically, a most important appendage of the earth. Necessary though it is to our life it constitutes one of the greatest obstructions with which the astronomer has to deal. It absorbs more or less of all the light that passes through it, and thus slightly changes the colour of the