Review of the New York Geological Reports. A7. 
ue; of the former many thousand tons are annually excavated. 
Several acidulous springs issuing from these deposites, have been 
found to contain free sulphuric acid. 
Water Lime Group. (A part of No. 6 of the Pennsylvania 
survey. )—For better distinction known also as the ‘‘ Manlius wa- 
ter lime,” since the terminal division of the last group, according 
to Hu, assumes, in the region around Cayuga Lake, the charac- 
ter of a water lime, and is employed, like the rock now to be de- 
scribed, as a hydraulic cement. 
The Manlius water limestone consists of drab colored layers 
interstratified in a mass of darker blue limestone. The thick- 
ness of the whole varies from thirty to a hundred feet, but only 
a few feet of this is suitable for hydraulic purposes. ‘The layer 
most highly esteemed for cement, is from four to five feet thick, 
of a drab color, and fine grained, traversed by oblique cracks in 
at least three directions, which causes it to break into irregular 
fragments. At some localities siliceous nodules are interspersed ; 
then it is no longer fit fora water lime. An interlamination of 
shale is also destructive of its economical value, since an excess 
of argillaceous matter is very injurious to such cements. 
The individual layers are not unfrequently interlocked by a 
notched surface not unlike the sutures of a skull; this appearance 
Vanoxem attributes to crystallizations of sulphate of magnesia. 
On the chart, the water lime is represented by a grayish blue 
band, narrow and rather tortuous in its course, whose general di- 
rection is nearly west and east, from Niagara river to Schoharie, 
thence with a southerly curve along the Helderberg range to the 
ating Valley. It exists also out of this general range in 
the base of Becraft’s Mountain and Mount Bob, outliers of the 
Helderberg, east of North River, near the city of Hudson. 
The typical fossils of the group given in the Reports, are em- 
braced in the following wood cut. 
Vanuxem’s Report, p. 112. 
Fig. 1. Delthyris plicatus. 2. Avicula rugosa, Conrap. 3. Tentaculites orna- 
tus, Sil. Res., p. 12, fig. 25. 4. Littorina antiqua, Conrap. 5. /trypa sulcata, 
Vasuxem. 6. Cytherina alta, Conrad. 
