510 
GEOLOGY OF THE FIRST DISTRICT. 
The crystallized serpentine also occurs at Warwick in the white limestone (Vide American 
Journal of Science, Vol. 9, p. 212). Professor Nuttall makes the angles 96° and 84° (Vide 
Robinson’s Catalogue of American Minerals, p. 296). 
October 11 , 1834. Another crystal of serpentine, obtained from Hustis’s quarry, measured 
with the reflective goniometer, gave the following angles. The planes were tolerably brilliant, 
but did not give a perfect reflection. The whole of the measurements are given. 
Fig. 27. 
m on T, 93°04^; 
m on i, 136 40 ; 
T on i, 135 50 ; 
93°00'; 92°58'. 
136 50; 136 50; 
135 40; 136 09; 
136°40'; 137°00'. 
136 04; 136 05. 
MEAN. 
93°00'40^' 
136 48 00 
135 59 36 
These mean angles exhibit a small error, the sum of w on T and the 
supplements = 180°12'4'''= to 12'4" excess. Correcting for this 
excess, the angles would be about m on T, 93°00' 
m on i, 136 54 
T on i, 136 06 
Dr. Barratt found a large weathered crystal of serpentine at Hustis’s quarry in 1821 or 
1822. His measurements of this rough crystal, with the common goniometer, are 115° 15' 
and 64° 45'; and Professor Shepard’s measurements of the same crystal, 115° and 64°; and 
others as follows : 
Fig. 28. 
Prof. Shepard’s and Dr. Barratt’s measurements of the same crystal differ more than ten 
degrees in one of the angles, and more than five degrees in another ; but this is not surprising, 
in consequence of the great irregularity of the faces, having been long weathered, and much 
worn and rounded. These measurements, of course, are too imperfect to be admitted in any 
investigations concerning the primary form. Prof. Shepard classes serpentine as a right rec¬ 
tangular prism {Treatise on Mineralogy, p. 168). The measurements that have been given, 
which were made with the reflective goniometer, may be depended on within a few minutes 
of a degree, and they indicate a doubly oblique prism, of which the following angles are ele¬ 
ments, viz : P on m = A = 99°26' 
P on T = B = 95 20 
m on T = C = 93 00 
