This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1843 Excerpt: ...as the carbonates of lead, baryta, strontian, potash, and ammonia; the bicarbonate of ammonia, and that variety of carbonate of lime called arragonite; the nitrates of potash, ammonia, and silver; the sulphates of magnesia, zinc, baryta, and strontian, and bisulphate of potash; Rochelle salt (tartrate of potash and soda) and emetic tartar (tartrate of potash and antimony). To the above must be added the following substances: topaz, dichroite, citric acid and morphia. Properties.--The crystals of this system present the following properties: they have three rectangular axes all of different lengths: they are doubly refracting with two optic axes; and are tri-unequiexpanding. Consequently they have three rectangular unequal elasticities. On the ellipsoidal hypothesis, their atoms are ellipsoids, with three unequal axes. They present no crystallographical character by which the principal axis can be distinguished from the others called secondary axes; so that in a geometrical point of view the choice of this axis is altogether arbitrary. But considered optically the principal axis is the middle point between the two nearest poles of no polarization. It corresponds with what is called by Mr. Brooke the prismatic axis; that is, the axis which passes through the centres of the terminal planes of the prism. If you examine one of the simple or primary forms of this system--say this unmodified rectangular prism (the outer prism of figure 39), you observe there is no single line around which the figure is symmetrical; nor any square plane, or plane which can be inscribed within the circle. But let each of the two opposite terminal edges be replaced by a square plane, both equally inclined to the prismatic axis, and the line which passes through the centre of each of ...
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