Fig. 37.
Note 162, [p. 106]. Analytical formula or expression. A combination of symbols or signs expressing or representing a series of calculation, and including every particular case that can arise from a general law.
Note 163, [p. 106]. Fig. 38 is a perfect octahedron. Sometimes its angles, A, X, a, a, &c., are truncated, or cut off. Sometimes a slice is cut off its edges A a, X a, a a, &c. Occasionally both these modifications take place.
Fig. 38.
Note 164, [p. 107]. Prismatic crystals of sulphate of nickel are somewhat like fig. 62, only that they are thin, like a hair.
Note 165, [p. 108]. Zinc, a metal either found as an ore or mixed with other metals. It is used in making brass.
Note 166, [p. 108]. A cube is a solid contained by six plane square surfaces, as fig. 39.
Fig. 39.