Page:Sir William Herschel, his life and works (1881).djvu/220

198 that he clearly distinguished the essential differences of the spectra of these stars, and that he made these observations in support of his statement that the fixed stars, "like the planets, also shine with differently colored light. That of Arcturus and Aldebaran, for instance, is as different from the light of Sirius and Capella as that of Mars and Saturn is from the light of Venus and Jupiter."

Of course, no special discovery can be claimed for him on these few instances. We can see, however, a good example of the manner in which he examined a subject from every side, and used the most remote evidence exactly in its proper place and time.

It is certainly a remarkable fact that was the first observer to recognize the real importance of the aperture or diameter of a telescope. Before his time it was generally assumed that this element only