From such measuring of distant objects on the surface of the earth, the passage was easy to an attempt to measure the distance of heavenly bodies. How far is the moon from us? It was soon found that a base of ten miles or of a hundred miles was entirely too short to give satisfactory angles. The moon was too distant. A far larger base was required. Suppose two places to be selected on the same meridian of longitude, and therefore agreeing in time, and situated sixty degrees of latitude apart. The distance between them will be equal to a radius of the earth. At each station, and at the same hours, the angles are taken which the moon makes with the zenith, or, better still, with some star near it, coming to the meridian at the same time. In such a case, the angles are, satisfactory. The base is large enough. The result of such observations, and of others which we need not dwell on, is that, when nearest to us, the centre of the moon is distant from the centre of the earth 222,430 miles; when at her greatest distance, 252,390 miles. These numbers are based on the fact that the equatorial radius or semi‐diameter of the earth is 3962.57 miles. This value, however, may in reality be a quarter of a mile too short. The mean distance of the moon is roughly stated at 60 semi‐diameters of the earth. When observers essayed to apply to the sun the same procedure which had proved so successful in regard to the moon, they encountered disastrous failures, partly because the base, even the largest practicable one, was found to be comparatively very small; partly because, when the sun shines, no star is visible near by from which to measure an angle; and also because the atmosphere is so disturbed by the rays of solar heat that, when seen through a large telescope, the sun’s edge is quite tremulous. Hence a very large element of uncertainty is introduced when angles are taken with the zenith. No astronomer would look with confidence on the result obtained under such circumstances. Two hundred years ago, their instruments were much less perfect than those we now have; yet, even with our best instruments, to‐day, too much uncertainty remains. That mode of ascertaining the sun’s distance has been abandoned.