_ bate ensu 
Se 
wae : 
ie , , a. 
174 Association of American Geologists. 
Dr. Jackson stated that the mass of infusorial deposit found 
under peat bogs is hydrate of silica, which loses by being heated 
to redness from 12 to 15 per cent., principally vegetable matter. 
Great abundance of this material occurs at Newfield, in Maine, 
where it covers many hundred acres, and is five or six feet thick. 
After burning, it is so white and beautiful that it has been fraud- 
ulently sold for magnesia alba. The ammonia which is evolved 
in its destructive distillation, is probably derived from the creni¢ 
and apocrenie acids which it contains. Phosphate of lime and 
manganese are found in it in small quantities. As a fertilizer of 
land, it is considered of use when containing in large quantity 
the juices of plants. ae 
A memoir from M. Alexandre Vattemare was presented, pro- 
posing a general system of exchange of objects of nature and 
art among all nations. It was by motion laid on the table. 
The subject of bowlders and diluvial scratches was then 
bronchi discussion by Prof. Mather, and a protracted de- 
ed, in which many of the members joined. ; 
__ Prof. Mather inferred from the facts in the case, that the 
bowlders and diluvial scratches had, in general, come from the 
north ; those on the east of the Hudson from the northwest, 
those on the west from the northeast, as by the result of two 
forces. = 
The diluvial furrows are, in general, parallel to the valleys in 
_ which they are found—thus in the small transverse valleys, the 
# 
scratches are found parallel to the direction of the valleys—and 
not coincident with those of the main valleys. All the bowl- 
ders seem to have been brought from the northwest, both at the 
east and beyond the river’ St. Peter’s at the west, and very few 
are found below 38° or 39° of north latitude. 
The chairman (Prof. Silliman) cited the recorded observa 
tions of Mr. C. Darwin, naturalist to H. M. ship Beagle, that 1 
South America no bowlders occur nearer the equator than about 
40° south latitude. : id re 
Prof. Mather had not seen any bowlders in the coal region of 
Ohio, and very few in Kentucky. He thought that the bowl 
ders mentioned by Mr. Hodge in the gold region of North Caro- 
lina, were not transported masses, but were composed of granite 
which had suffered decomposition in situ by atmospheric agenCY: 
: ~ * 
