uite homogeneous. The p 
terial appeared to ae 
could be selected containe 
as follows ae 
Silicic acid, - . . - 1632, 39 
Alumina, . - rs . rs ‘ -  144tom 
Ferric oxyd, . - . e . . 0°88 
Maguay ee 
Lime, - Be scunket i Sa ee oo 
Potash, - : i j : ; : 401 
Ignition, - - - - - - - 0°64 
10001 
It will be observed that the composition of Bunsen’s toni 
constitution of trachyte, to which the porphyries belong, closely 
resembles the above, containing : 
i Al, Pe Ca Mg KNa 
4667 1423 1:44 0:28 38 
11, Staurotide ? : 
I have examined the mineral, that Prof. C. U. Shepard, 12 
his Report on the Canton Mine, first noticed as Staurotide of 
supposed Partschine, and of which Prof. W. J. Taylor found a 
of quite pure material, using the utmost care to obtain pér 
fectly correct results. 
It occurs in minute crystals, rarely of 4 of an inch in length, 
of a yellowish brown or cinnamon brown color, apparently right 
rhombic prisms, similar to those of staurotide with the planes 
ages I have not observed any others, Sp. gr. at 
Associated with the copper and lead ores of the Canton Mine, 
and very characteristic for this locality. I obtained: ~ . ; 
iL Il. TL aY. Oxygen. 
Mean result. ‘ 
1°91. 1°25 136... 3 (ae, 
28°72 28°87 2888 28°82 contains 14-96 } 15°29 = 580 
0°88 0-70 “ 0°33 % 
2 4942 4920 4991 « 923-00 05°85 =9 
9-34 6 955 2°85 ‘e 
649 Ve 
rr eS: 
e3 66 "1g. « 1-41 a 
det, brat 015 O15 « oo} 273=1 
eo BOY fe 
