a fruitful field for genius and perseverance to cultivate. "Its causes and laws are hid for the present in almost equal obscurity," was the judgment of Dr. Maskelyne, then Astronomer-Royal; but it pointed to changes among the stars, which a shrewd observer would endeavour to ascertain and account for. Herschel undertook the work. Availing himself of a catalogue of 2884 stars published in 1723 by Flamsteed, the first Astronomer-Royal, he compared the heavens of his own day with the appearance they presented then. He had no star charts such as astronomers have since constructed, and which, when compared with a revised edition a century hence, may reveal much that is at present dark regarding the motions and destiny of the small but beautiful home of our shortlived race. He had no photographic plates to expose or consult. From beginning to end it was eye-labour and hand-labour with this intrepid traveller among these far-away suns. So laborious was the comparison that he had "many a night, in the course of eleven or twelve hours of observation, carefully and singly examined not less than 400 celestial objects, besides taking measures of angles and positions of some of them with proper micrometers, and sometimes viewing a particular star for half an hour together, with all the various powers of his telescope." During that interval of sixty years he found that stars had been lost or had vanished, that they had undergone some capital change of position or magnitude, or had come into sight where they were not previously seen, although "it is not easy to prove a star to be newly come" into any part of the sky. If a star suddenly shone out so as to attract the eyes
