512 
GEOLOGY OF THE FIRST DISTRICT. 
tang i (D -E) = t^g.Y (D+E)_(e-^) _ EC . sin C _ 
(e+a) ' sin D 
The ratios of the three edges of the defect on the primary plane P, are, 
CD : CE : DE : : 1015-57 : 1010-93 : 1470*00. 
The ratios of the two edges CD and CE are so nearly equal, that we may infer the law of 
decrement on the edge CA^ to be one row of molecules; and that the line DE is parallel to 
the diagonal of P, and consequently the edges of the primary form, on the plane P, bear the 
same ratio as the lines DC and EC, viz. 1015-57 : 1010-93. The angles of the plane (/) 
are too uncertain to attempt the determination of the law of decrement on that edge, and the 
ratio of the remaining edge of the primary form. This is still a desideratum. 
2 . HIGHLANDITE, ALLANITE? (Supposed to be.) 
It has not been analyzed, unless Prof. Beck has procured specimens and analyzed it. 
This mineral occurs at the white augite and coccolite locality near Mr. Potter’s, about one 
mile northwest of Fort Montgomery. It also occurs on the east side of the Hudson, on the 
neck of land on which the “old silver mine” is located, about five miles south of West-Point. 
Characters. It is black, and dark-bottle green; lustre resinous on the fracture, but on the 
surface of crystals it is strongly shining, almost splendent, and semi-metallic. It does not 
yield to the knife, and scratches glass. It has much the aspect of dark colored crystals of the 
oxide of tin, but its specific gravity does not exceed 4. It is fusible with much intumescence 
into a greyish slag on charcoal, and does not become magnetic. With borax it fuses and gives 
a slightly colored yellow globule, with an undissolved skeleton within; I have often observed 
this mineral in connection with the limestone and augite rocks, between West-Point and the 
Dunderberg mountain, on both sides of the Hudson. 
The following angles were measured with the reflective goniometer. 
The planes were brilliant, and gave good reflections, except the small 
plane (6). a on c, 129°04' 
a on d, 128 10 
a on e, 150 00 
a on e', 119 42 
a on h, 159 00. This plane (Jb) is striated, and a 
good reflection was not obtained. The common goniometer gave a on h, 161°. 
These measurements were made in June, 1833. 
3. RED TABULAR MINERAL. (Probably new.) 
This was sent to me by Dr. Young, in October, 1832. 
It is found in the white limestone near Amity, Orange county. It is in small tabular masses 
