and its Contact Phenomena. - 381 
stratification. This arm is shown in fig.4. The impregnation 
: of the schists with tourmaline 
has been much more effectual 
below than upon the summit. 
Two hundred feet below the 
summit the schists distant 100 
feet from the contact contain 
as many tourmalines as at 
fifteen feet from the contact 
upon the top. The mixed 
zone steadily ven biggest in 
iia. ge _ width as it descends, and at 
nstion of schist and Albany grant he base of the huge cliff it 
the schist. Scale 75 feet to one inch. is more than twenty feet 
wide 
These are the main features of this remarkablecontact. I think 
schists, and that the main portion of its mass had not erystal- 
lized at the time of eruption. The inclusion of such varied 
products in the mixed zone indicates that it moved no incon- 
siderable distance through fissures in very diverse rocks. The 
kind of impregnation indicates that it was accomplished by 
vapors and solutions that emanated from the fissures filled by 
the granite; but the impregnation of schists embedded in the 
granite, and the impregnation of the schists attendant with a 
dehydration of the same, indicates the action of very hot 
vapors which accompanied the eruption; not the action of 
vapors subsequently emanated through the cleft.* 
The line of division forming the contact is microscopically 
fine. Over this line the minerals of schist or granite do no 
pass except in the form of inclusions. There is therefore no 
other areas of Albany granite as far as observed, the effects of 
the contact are found upon the edges of the granite. At 
Ft cavities in the quartz of the granite contain most variable amounts of fluid. 
are full and some are empty. The calculation of temperatures and pres- 
ei measured size of bubble and cavity can be of little value when, as 1s 
Plain, other unknown quantities beside those commonly considered are 
