146 Association of American Greologists and Naturalists. 
Half way up the mountain large masses of the slate, many upwards of 
100 Ibs. weight, were found imbedded in the granite ; further up was a 
breccia. of granite and slate, in which the latter is found varying in size 
from a diameter of several feet to less than one inch, mixed up with 
the granite in the greatest possible confusion ; the slate standing in ev- 
ery. possible position was aptly compared on the spot to the books of 
an extensive library scattered about. Passing over this breccia for the 
eighth of a mile, we find a finer breccia; at the summit only fine scales 
of the slate are found in the granite. We learn from this locality that 
the changes effected by the granite are very slight; the angles of the 
fragments are preserved, and there is no appearance of fusion. At the 
lower part of the mountain, changes in the structure are evident, but 
none in the form. The conclusion forces itself upon the mind, that 
here the granite was not intensely heated, or else that it is a very poor 
conductor of heat; that it was not liquid, but in the state of a thick 
paste. is leads to a consideration of the absence of vesicles, for the 
formation of which a pasty state is not favorable. The density of the 
paste. may be estimated from the fact of magnetic iron in masses of 
several inches in diameter being found imbedded in it. . If the granite 
had been in a liquid state, the iron would have sunk to the bottom. . Dr. 
J. exhibited a hand specimen showing the drift scratches, which would 
be appreciated by those who knew the difficulty of obtaining small 
characteristic specimens. The mountain was coyered with these 
scratches ; they were from. N. 10° W. to S. 10° E.. The occurrence 
of metamorphic rocks is frequent in New Hampshire, Maine, and Ver- 
mont. An examination of the line of junction between the slate and 
granite shows that the eruption took place immediately after the depo- 
sition of the oldest argillaceous slate, and that it is much older than the 
granites of Switzerland. . 
_ Prof. E. Emmons then exhibited specimens, showing the ef 
fects of alteration by artificial heat, producing a columnar struc- 
ture resembling basalt in a piece of the Potsdam sandrock, which 
had for many years been used as the hearth of an iron furnace; 
also a mass of sand altered by similar means. He instanced a 
trap dyke passing through the calciferous sandrock of Eaton, and 
converting the adjoining portions into a rock resembling white 
crystalline limestone. Prof. E. adverted to these as. instances of 
_ change effected by dry heat. He then showed other specimens 
which he supposed to have been altered by the aid of heat and 
‘Water conjointly ; among these are specimens of calcareous spat; 
coated with chalcedony and other Rossie specimens. Prof. E. 
would divide the effects of heat under two heads ; first, dry heat j 
and second, the conjoined effects of heat and water. | 
