Geology. 427. 
The sensitizing bath is _ 
6 grammes pure nitrate of silver 
1 x “ water. 
Albumenize with 
110 grammes albumen. 
s water, 
050 “ — iodid of ammonium. 
‘ *¢ —_bromid of ammonium. 
Shortly before exposing the plate it is again sensitized in a bath com- 
of— 
8 grammes pure nitrate of silver. 
8 “ glacial acetic acid. 
100 centimeters pure water. ' 
. - is afterwards slowly dipped in fresh water and set up in a dark place 
After exposure develop by a bath of— 
10 r. 
es water. 
05 “  pyrogallic acid. 
vy acetic acid. 
This developing bath should be heated to 120° Fah. Strengthen by 
re-development with pyrogallic acid. Fix as usual. E. E. 
II. GEOLOGY. 
which he described under the name of the Taconic system, and regarded as 
older than those supposed by his colleagues to represent the Silurian series. 
ccording to Dr. Emmons this system, which he divides into an upper 
and lower portion, has a thickness of 30,000 feet, and extends throughout 
the whole Appalachian chain. He has descri it as composed in 
ascending order of, 1. Granular quartz. 2. The Stockbridge limestone. 
ye esian slates. 4. Sparry limestone. 5. Roofing slates (grapto- 
litie). “6. Silicious conglomerate. 7. Taconic slates. 8. Black. slates. 
This is not their apparent order of superposition, but Dr. Emmons con- 
ceives that the whole series has been inverted since its deposition. In fact 
the schistose strata 5, 6, 7 and 8, pass successively beneath the magnesian 
slates and limestones, which in their turn are overlaid to the east by the 
