. Annals of the Lyceum of Natural History of New-York. Science. of the Trimetric System. 53 axes, angles (measured over the extremity of the other axis) nearly alike, this other axis is the true vertical, and the vertical prism is near 90° in angle. Polymignite is near Wohlerite in its crystallization. With the fundamental form adopted, the known octahedron is 22 (2P2), and the occurring prisms are IS = 109° 46', 21 = 70° 50', 4a = 39° 9'. Polycrase affords angles in three directions near 90°, which- ever position be taken. In the figure annexed, the position and lettering correspond to the di
. Annals of the Lyceum of Natural History of New-York. Science. of the Trimetric System. 53 axes, angles (measured over the extremity of the other axis) nearly alike, this other axis is the true vertical, and the vertical prism is near 90° in angle. Polymignite is near Wohlerite in its crystallization. With the fundamental form adopted, the known octahedron is 22 (2P2), and the occurring prisms are IS = 109° 46', 21 = 70° 50', 4a = 39° 9'. Polycrase affords angles in three directions near 90°, which- ever position be taken. In the figure annexed, the position and lettering correspond to the dimensions given in the table. Should we change it, and make the brachydiagonal the vertical axis, then : 1 = 93° 52', U = 91° 29', IS = 95° 2'. And, again, if we make the macrodiagonal the vertical axis:. /= 91° 29', 11 = 84° 58', It = 86° 8'. The symbols of these planes in these three positions (which we may call A, B, C,) are as follows : A (figure) 1 13 21 il iS ii B 1 3 ^:2 0 (base) Si il C 1 13 hi il \% O(base) The form is near to Bournonite. It is also related dis- tantly to the Columbite species, the prominent difference being, jive degrees in the angle of the vertical prism. The species of Table II. fall into four sections, depending'on the angles of the unit domes. MARCH, 1854. 5 Ann. Lyc. Nat. Hist. Vol. 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 Lyceum of Natural History (New York, N. Y. ). New-York :
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