196 
Relief process was also illustrated. He pointed out the great 
value of such processes to the naturalist, who would in this 
way be able to have preserved in permanent pictures, repre- 
sentations true to nature of the objects of his study. Some 
of Mr. Rockwood’s specimens were of a very remarkable 
character, as, for instance, a complete copy of the London 
Times reproduced in a page only 4$ by 34 inches, and 
Harper's Weekly only 3 by 2 inches, and which latter can 
yet be easily read by means of a lens. 
The President expressed his earnest hope that scientists 
would have in this or some similar process, the long-looked- 
for means of representing objects of natural history, in a 
cheap and truthful manner. It would seem as if we were 
on the eve of the accomplishment of this great end, and 
that perhaps we were about to enjoy what those who had 
gone before us had unsuccessfully longed for. The pictures 
exhibited certainly held forth great promise for the future. 
Pror. H. Wurtz called attention to some analyses, made 
by Dr. P. Schweitzer, of Sandstones from New Jersey. They 
were as follows: 
ScHWEITZER. Cook. 
a. | b. { c. | Bergen Hill. 
Si 08 67°4 T77 73°8 526 
Al?02 } 16°63 a is3 es eT 
Fe203 § ? 1:9 3°8 8-7 
CaO | 06 Leh 78 
MeO : 0-4 ns 10°6 
MaOask fiinte 6-9 6-9 1:3 
KO ‘ny I s 0-9 
HO ——_ 0°8 iy 
a. and b. are from Newark, the latter being one of the 
specimens procured by Prof. Edwards, c. is from Haver- 
straw, 100 feet beneath the Trap rock. Prof. Cook's analysis 
is given for comparison. In Dr. Schweitzer’s analyses the 
operations were conducted with great care, and the portions 
soluble and insoluble in boiling Hydrochloric acid determined. 
It is noticeable that the amount of Alumina present cor- 
responds to 58-4 per cent. of Albite or normal Soda Felspar. 
