Diamonds and precious stones, a popular account of gems .. (1874)
Dieulafait, Louis, b. 1830, Sanford, Fanchon, tr · New York, Scribner, Armstrong, and Company · leaf 44
be evident. If the experiment is made at night, instead of apin a lighted candle may be used, the candle beingplaced beyond the reach of currents of air, so thatits flame may be pure and regular. The pheno- OPTICAL PROPERTIES. 23 menon will be exactly the same, and have the aspectpresented by Fig.… … Fig. 18.—Aspect of a candle seen through a doubly-refractive crystal. metric) system, possesses simple refraction. Thestone experimented on, therefore, is no doubt oneof those with which the diamond is sometimes con-founded, such as the sapphire and the zircon, whichpossess double refraction.…
Precious stones · Diamonds · Gems
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