100° T. 8S. Hunt on Lithology. 
manganese reaction. From the residue after the action of the 
nitric acid, a solution of carbonate of soda removed a portion of 
silica ; and the remainder, dried at 300° F., was free from iron 
and from manganese. Its ivan is given "under 1x, while that 
of the matter dissolved by nitric acid and a of soda 
from 100 parts of the rock will ie found under 1x 
A dike of trachyte near to the last, and very esa to it in 
appearance, was submitted to the action of nitric acid, but the 
insoluble residue was not treated by carbonate of soda, Its 
analysis is given under x, while that of the soluble matters is to 
be found under xa. A white trachyte from a dike at Lachine 
resembled the preceding, but was somewhat earthy in its aspect, 
and effervesced with nitrie acid, which removed a portion of lime 
equal to 7-40 per cent of carbonate. On boiling the pulverized 
rock with nitrate of ammonia, an amount of lime equal to 5°33 
per cent.of carbonate was dissolved. An accident prevented the 
complete determination of the alkalies in the feldspathic residue 
of this trachyte; and the soluble silica was not removed pre- 
vious to the fs ea whose result is given under xI. The pro-' 
portion of the potash to the soda was however found to be, by 
weight, nearly as two to —_ The matters dissolved by nitric 
acid will be found under 
Another dike of eclivts “from Lachine was concretionary, 
and stained by infiltration; the interior of the concretions was 
white and earthy. The substances removed from 100 parts of 
the rock by nitric acid and carbonate of soda, are given under 
analysis of the insoluble residue showed it to 
feldspar see to those of the preceding trachytes; the quantities 
of potash and soda were however nearly in the ratio of four to 
é 
ree. 
A large dike of trachyte in the limestone quarries at the Mile . 
End, near Montreal, is remarkable for the amount of carbonates 
which it contains. It is grayish-white, with dark gray spots, ) 
granular, sub-vitreous in lustre, an holds a few erystals of horn- 
blende. By ignition it loses 11-0 per cent of its weight. In 
powder it effervesces freely with nitric acid, disengaging carbonic 
acid, and, when heat is applied, red fumes from the peroxyda- 
tion of the iron. One hundred parts of the rock yielded in this 
way the soluble matters given under x11a. The composition 
the residue, from which the soluble silica was not removed, is 
ay under XIL 
Tx. x. x. xi, 
ne _ Silica, - - - - *68°26 62:90 53°50 61°62 
