Page:Popular Science Monthly Volume 60.djvu/304

296 as illustrated by the photographs themselves (compare Fig. 3 with Fig. 4). The small cluster, which in reality contains several thousands of stars, is resolved by Mr. Ritchey's photograph taken with the large telescope into all its constituent parts, stars less than one second of arc apart being clearly separated on this great scale.

Having seen this illustration of the superior power of the large telescope you may perhaps be interested to become more closely acquainted with the instrument itself (Fig. 5). The great weight of the 40-inch lens, amounting with its cell to half a ton, requires that the tube which supports it, here taking the place of the camera box of the previous instrument, shall be of immense rigidity and strength. This