. Bulletin of the Department of Geology. Geology. Eakle.] Colemanite from Southern California. 43 It' with a radius of h = 1 = c-axis, a circle is described, then this circle would represent in ground plan a sphere of projection. The plane of projection would be tangent to this sphere at the end of the c-axis, 8 would be the pole of the projection, and 8Y the first meridian. Any faee pq would have the point of inter- section of its normal with this plane, located by the angle which it makes with the first meridian 8Y, and the distance from the pole df = tg p. (Figure 1). The face pq is further
. Bulletin of the Department of Geology. Geology. Eakle.] Colemanite from Southern California. 43 It' with a radius of h = 1 = c-axis, a circle is described, then this circle would represent in ground plan a sphere of projection. The plane of projection would be tangent to this sphere at the end of the c-axis, 8 would be the pole of the projection, and 8Y the first meridian. Any faee pq would have the point of inter- section of its normal with this plane, located by the angle which it makes with the first meridian 8Y, and the distance from the pole df = tg p. (Figure 1). The face pq is further defined by the two rectangular coordinates % y , whose values deduced from the right triangles are x — sin 4> tg p y' = cos 4> tg p. By means of the measured y angles and p, all forms can be plotted on cross section paper, and the co- ordinates x' y' give graph- ically the symbols for any form in terms of the ./ y/ of the unit form pq. In monoclinic crystals the projection of the base-normal lies in front of the pole at a dis- tance e = tg p, and the distances p'0 and q'0 are the coordinates for the unit pyramid pq reckoned from the base; therefore for any values of pq, / = pp'0 + (/ and y' = qq'0. Determination of /, p-, and P.—An average of twenty read- ings on the basal pinacoid gave p = 20°7, with = 90°; e' = tg p = This value of e/ was also obtained from the readings of the clinodomes. For these forms x = e', and an average of forty-four values of / for the domes 01 and 02 gave ,/ = ; thus agreeing with the direct measurements. Also ,/ = Cot p. = 6!)° 53' and j8 = 180° — /* = 110° 7'. Determination of //,, and tg p y = cos tg p the coordinates x' y' were calculated for all the best faces. For. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original University of California, Berke
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectgeology, bookyear1902
