Page:Herschel - A Preliminary Discourse on the Study of Natural Philosophy (1831).djvu/48

 there ought to be no darkness,—in fact, no shadow at that place; but, on the contrary, a degree of illumination precisely as bright as if the metal plate were away. Strange and even impossible as this conclusion may seem, it has been put to the trial, and found perfectly correct.

(25.) We shall now proceed to consider more particularly, and in detail,—