202 PHILOSOPHICAL TRANSACTIONS. |_ANNO 1/82. 



of nature; why this method should not be more pursued in the art of seeing 

 does not appear. Theories are only to be used when proper data are assigned; 

 but the data are carefully to be re-examined, when new improvements may widely 

 alter the result of former experiments. Thus, we are told, that we gain nothing 

 by magnifying too much. I grant it; but shall never believe I magnify too 

 much till by experience I find, that I can see better with a lower power. Nor 

 is even that sufficient: a lower power may show more of the object; it may show 

 it brighter, nay even distincter, and therefore on the whole belter; and yet the 

 greater power may, in a particular case, be preferable: for if the object is so 

 small as not to be at all visible with the lower power, and I can, by magnifying 

 more, obtain a view of it, though neither so bright nor distinct as I could wish, 

 is it not evident, that here this power is preferable to the former ? 



The naturalist does not think himself obliged to account for all the phenomena 

 he may observe; the astronomer and optician may claim the same privilege. 

 When we increase the power we lessen the light in the inverse ratio of the square 

 of the power; and telescopes will, in general, discover more small stars, the 

 more light they collect; yet with a power of 227 I cannot see the small star 

 near the star following o Aquilae, when, by the same telescope, it appears very 

 plainly with the power of 460: now, in the latter case, the power being more 

 than double, the light is less than the fourth part of the former. In such par- 

 ticular cases I generally suspect my own eyes, and have recourse to those of my 

 friends. I had the pleasure of showing this star to Dr. Watson, junior, who 

 soon discovered the small star, which accompanies the other, with the power of 

 460 ; but saw nothing of it with 227, though the place where to look for it had 

 been pointed out to him by the higher power. The experiment has been too 

 often repeated to be doubtful, and has also been confirmed by others of nearly 

 the same nature: for instance, the smallest of the 2 that accompany the star 

 near h Aquilae, the small star near ^ Herculis, and the small star near « Lyrae, 

 are invisible with my power of 227, but visible with the same aperture when 

 the power is 460. Also the small stars near Flamsteed's 24th of Aquila, the 

 smaller of 2 near 0- Coronas, the small star near the star south of t Aquilas, the 

 small star near the second o Persei, the small star near the star which accom- 

 panies Flamsteed's 10th sub pede et scapula dextra Tauri, the small star near |3 

 Delphini, and the small star near the pole star, are all much brighter and 

 stronger, and therefore much sooner seen with 4fjo, than with 227. 



Great power may also, in particular circumstances, be favourable, even with 

 an excess of aberration. When two stars are so close together as to make the 

 scale for measuring the distance of their centres too small, if, by magnifying 

 much, we can enlarge that distance, we may gain a considerable advantage, pro- 

 vided the centres, or apparent bodies of the stars, remain distinct enough for the 



