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Rh them are not merely double in appearance, but must be allowed to be real binary combinations of two stars, intimately held together by the bond of mutual attraction."

Herschel's first catalogue of double stars was presented to the Royal Society in a memoir of fifty pages on January 10, 1782. It was a work of enormous labour to be undertaken and carried out by a hard-working musician during the nights, that followed days of absorbing business. Of the number 269, contained in this catalogue, 227 had not been noted by any astronomer before him. It was not only a new field of research he may be considered to have opened up. He had also two distinct ends in view, which may be said to have been equally novel. One of them was, by means of these double or triple systems, to discover the distances of the stars from our sun, and the other to ascertain whether "small stars revolved round large ones." He failed in the former, he was successful in the latter. The arithmetic of the one was too hard for him; the poetry of the other was reduced to the commonplace of fact, after a waiting period of twenty-five years.

Everyone knows that if a tree and a house be in the same line of sight from a distant spectator, the eye of the spectator may imagine the tree to be at the same distance as the house, but cannot measure the space between them. We cannot see distance; it is an acquirement gained by experience from the sense of touch, and gained so insensibly that we think we see distance in front of us, height or depth, it may be, while, in fact, we only see length and breadth. An observer, seeing two stars so close that, to the naked eye, they seem only one, may consider