Geology and Mineralogy. 1538 
= Is visible; and finally to masses, “ batholiths,” which never 
the surface in fluid condition but which solidified in the 
depths, and of which evidence is sometimes had in the altered 
strata which formed a part of the original covering. The author 
thus passes from the ash deposits of the present to the granite. 
masses of the Erzgebirge and the Drammen granite of Norway, 
and to the complex relations of the granites of the Alps. 
The concluding chapter is devoted to the different classes of 
earthquakes, and their relation to earlier and more extensive 
movements in the earth’s crust. 
This memoir by Professor Suess promises, when completed, to 
be an important contribution to geological science. The author's 
extensive reading, together with his personal observations, gives 
im a wide and varied range of illustrations, which add much to 
the interest of his writings. 
4. Unconformability between the Upper and Lower Silurian 
Formations in New Jersey, bearing on the question as to the limits 
of the Green Mountain disturbance. (Letter from Prof. G. H. 
00K to J. D. Dana, dated New Bruns vick, N. J., Jan. 12, 1884.) 
~I notice in your comments on the Pennsylvania Geological 
w Jer 
1868, p. 135, is a wood cut made to show the unconformability 
of the two rocks at Otisville. This was made from a sketch 
drawn on the spot in 1867. The various localities about Rondout 
ave undoubtedly the best exposures for seeing the unconform- 
ability of these Upper and Lower Silurian rocks. Professor 
Smock and myself examined them in 1867, when we were looking 
for good examples to show the relation of these rocks to eae 
other in New Jersey. 
5. General Geological Map of the area explored and mapped 
¥. V. Hayden, from the surveys under his charge, 1869 to 
°F 41°03 miles to the inch. gee ae 
8 Emeralds from North Carolina.—At a recent meeting ee 
7 
