The American journal of science and arts . e,having the acute lateral solid angles replaced by tangent planes. The *Dr. Wollaston, in the Annals of Philosophy, Vol. V, p. 237, describes iodine asforming octahedral crystals, whose axes are to each other in the proportion of thenumbers 2, 3, and 4: also in rhombic plates, bevelled at their edges by two narrowplanes, inclined to each other under an angle of 120° 30, from the frequent occur-rence of which he remarks, that some crystallographers may be disposed to regardthis rhombic plate (of which the acute angle is about 53°) as a modification of
The American journal of science and arts . e,having the acute lateral solid angles replaced by tangent planes. The *Dr. Wollaston, in the Annals of Philosophy, Vol. V, p. 237, describes iodine asforming octahedral crystals, whose axes are to each other in the proportion of thenumbers 2, 3, and 4: also in rhombic plates, bevelled at their edges by two narrowplanes, inclined to each other under an angle of 120° 30, from the frequent occur-rence of which he remarks, that some crystallographers may be disposed to regardthis rhombic plate (of which the acute angle is about 53°) as a modification of arhombic prism, whose diagonals are 2 and 4, and its height 3:—the modification ofthe octahedron being derivable from either Mith equal facility.—Ed. On the Transition Rocks of the Cataraqul ^85 inclination of one of these secondary, with one of the adjacent planes,was determined by the reflective goniometer; but no more of theangles could be measured by this instrument, on account of the va-por from the crystal affecting the P on n 120° reflective goni-[o on P 120° common F on 11 120° Plane angle at a 44° h 136° From these, the plane an-gles, and the inclination of theSplanes to each other, werecalculated. P on V 142° 08 20 Pon/ 73° 1050 Plane angles at A 38° 56- a u a g 62° 29 I 78° 35 The axis is to the greater diagonal of the base, :: 3 :2, and tothe shorter diagonal, :: 3 : 15 or more accm-ately, A A : EE: II:: 1 : .497 : .355. These measurements must not be considered asperfectly accurate; but rather as approximations. p a Art. XVIII.—Ok the Transition Rocks of the Cataraqui; byCapt. R. H. BoNNYCASTLE, R. E. Canada. (Communicated for this Journal.) TO THE EDITOR. Sir—Conceiving that any circumstances tending to throw light onthe ages of rocks, must prove interesting in the present state of geo-logical science, and also apprehending that there are few which pre-sent more singular appearances than those I am about to undertakea feeble exa
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