PHYSICAL AND MATHEMATICAL SCIENCES. 291

high refractive power ; hence he hazarded the conjecture(so completely verified by modern discoveries), thatthe diamond “ is an unctuous substance coagulated.”

It appears highly probable that, about the period ofthe researches to which we have alluded, Newton wasengaged in repeating and varying the experiments ofGrimaldi on the inflexion of light before mentioned,and most probably before Hooke had communicated tothe Royal Society his experiments, which was in 1 f>74-.The account of these researches was not published till itappeared in the “ Optics ” in 1704; and he then speaksof them as investigations carried on long before, andput together out of scattered papers. His attention wasdirected entirely to the fringes formed externally alongthe edges of the shadows of bodies in light divergingfrom a single point; and having subjected these to veryprecise measurements, he framed a theory to explainthe manner in which the rays might be inflected inpassing by the edge of an opaque body. He also showedsome curious forms which' the fringes assume whenopaque edges are made to approach each other, so as toform an aperture through which the light passes: inthis case the effect is considerably complicated, especiallywhen the sides of the aperture are inclined to eachother, which was one case of which he has given a veryparticular account. He has also mentioned some otherresults, which are of a nature hardly intelligible, butwhich were left, as he tells us, in an unfinished state.“ I designed,” he says, “ to repeat most of them withmore care and exactness. ... But I was then interruptedand cannot now think of taking these things into con-sideration.” We have occasion on all grounds to de-plore the loss of his further examination of the subject,but on none more than the probable reason suggestedby Sir J. Herschel;—“ doubtless owing to the chagrinand opposition his optical discoveries produced to him ;an unmeet reward, it must be allowed, for so noble awork, but one of which unhappily, the history of scienceaffords but too many parallels.” (On Light. Art. 742.)u 2