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Rh deserved, and they only became an object of especial interest to students of physics when they were again studied by the famous German optician, a generation later.

Incidentally the experiments are of interest, as yielding us a measure of the excellence of telescopes, and a measure which is quite independent of the keenness of his vision. From them we may be sure that the efficiency of the nine-inch mirror used was not sensibly less than that of the highest theoretically attainable excellence. In this connection, too, we may refer to the Philosophical Transactions for 1790, pp. 468 and 475, where gives observations of both Enceladus and Mimas seen in contact with the ball of Saturn. I have never seen so good definition, telescopic and atmospheric, as he must have had on these occasions.

The spectroscope was applied by to the study of the spectra of the fixed stars