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Sec. II, Ch. 1: The Diamond

Sec. II, Ch. 1: The Diamond Page of 366 Sec. II, Ch. 1: The Diamond Text size:minus plus Restore normal size   Mail page  Print this page
56                                 The Diamond.
to the conclusion that the Australian Diamonds are harder and tougher than the stones from India, Borneo and Brazil, while these again have a hardness superior to that of most of the stones from South Africa.
Optical Properties.—Refraction.
The conditions which the Diamond presents in rela­tion to light are very remarkable. It is one of those bodies which refract light most strongly—that is to say, when a ray of light enters a Diamond, it is turned from its original path to a much greater extent than if it had entered a Topaz, or a Rock-Crystal, or a piece of glass, or, in fact, any other transparent medium. Hence the magnifying power of a Diamond is much greater than that of glass. It is said that if a Diamond and a piece of plate-glass be ground into lenses of similar form, the magnifying power of the Diamond will exceed that of glass in the ratio of 8 to 3. It was this that induced Mr. A. Pritchard, many years ago, to apply the Diamond as a microscopic lens ; but owing to the great difficulty of manipulating it, so as to adapt it to the purpose, as well as its intrinsic value, its use was extremely restricted.
As the Diamond is found in nature as a crystalline solid substance, of distinct form, it has naturally been generally assumed to be a mineral production. Probably the first philosopher to throw doubt on this conclusion was Sir Isaac Newton. In his remarkable optical researches he had established a definite relation between the refractive power of a body and its density. The power of refraction in each body is expressed scientifically by a certain number, or numerical ratio, called the index of refraction.
Sec. II, Ch. 1: The Diamond Page of 366 Sec. II, Ch. 1: The Diamond
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