. Annals of the Lyceum of Natural History of New-York. Science. of the Trimetric System. TABLE III. Angle of Vertical Prism, near 109° 28'. 59 I. Marcasite, . . II. Mispickel, . . Leucopyrite, . Aurotellurite, . Prism /. 106° 5' 111° 53' 1110 30' 110° 48' Dome Axes b : 1 : 1,7588 : 1 : : 1 : The angle of the vertical prism in Table III. is near the angle of a regular octahedron (109° 28'). As this prism is a cleavage prism, and the only distinct one in the species, it ap- pears to be the true vertical prism. But if we give the species another position, w
. Annals of the Lyceum of Natural History of New-York. Science. of the Trimetric System. TABLE III. Angle of Vertical Prism, near 109° 28'. 59 I. Marcasite, . . II. Mispickel, . . Leucopyrite, . Aurotellurite, . Prism /. 106° 5' 111° 53' 1110 30' 110° 48' Dome Axes b : 1 : 1,7588 : 1 : : 1 : The angle of the vertical prism in Table III. is near the angle of a regular octahedron (109° 28'). As this prism is a cleavage prism, and the only distinct one in the species, it ap- pears to be the true vertical prism. But if we give the species another position, we may exhibit a relation to sections II. and III. of Table II.; and as they are all related to the species of those sections in composition, this relation is of fundamental interest. Making the brachydome 11 the vertical prism, then the angle given above for the vertical prism is the new macrodome, and the supplement of that for the macrodome is the new brachydome. This gives for Mis- pickel the angles /: /= 99° 52'; li : li ?= 111° 53'; It : 11 = 120° 46'. If we now double the length of the vertical axis, the dome 1110 53' becomes §t, and 120° 46' ii; and the three angles will be 1:1= 99° 52' 5 H : U = 72° 58'; It : It = 82° 40', which are almost identical with the angles in Orpiment. The following table presents the angles and axes of the species thus changed in position, and also those referred to on Table II. It appears from the table that Marcasite, Fe S2, is very near Sul- phur in its angles and axes ; while Aurotellurite (Ag, Au), Te2, and Mispickel, Fe (S, As)2, to which Leucopyrite, Fe As4, should be added, have the form nearly of Orpiment. It is a question, therefore, whether Table III. should not be suppressed, and the. 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
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