WESTERN DISTRICT. 
275 
The above analysis represents the composition of the western hydraulic limestone. The 
same series exist, however, in Ulster county. Their analysis was made by Dr. Jackson, 
and gave the following result: 
Water ___ 1*182 
Silicic acid____ 10*087 
Carbonic acid.... 41 *200 
Sulphuric acid_ 0*606 
Lime .. 25*087 
Alumina_._ 3*395 
Peroxide of iron_ 3*274 
Magnesia. 12*890 
Oxide of manganese_ 0*606 
Potash_...._ 0*700 
Soda... 2*182 
100*000 
One hundred grains of the powdered rock give one grain of soluble matter ; of which 
there remains after ignition, 0*56 of a grain, leaving 0*44 for vegetable matter princi¬ 
pally.* 
From the several analyses, it will be observed that magnesia is an important and con¬ 
stant constituent of the shales and hydraulic limestones. The superior rocks contain a 
larger proportion than the inferior or gypseous deposits. There is no doubt this element 
exerts a beneficial inlluence on the crops, especially maize and the cereals. The question 
has been agitated whether magnesian rocks were favorable to vegetation. It seems to be 
set at rest by observation in New-York, where magnesian rocks are so prevalent. No part 
of the State is more fertile than those underlaid with the magnesian rocks. The same 
view is supported by observations in Berkshire (Mass.), where the dolomites prevail. 
Here the most fertile lands are underlaid by magnesian deposits. When, however, a 
magnesian limestone is burnt and converted into a caustic condition, the magnesia remains 
a long time, and if used before it is nearly saturated with carbonic acid and water, it injures 
vegetation ; but when slacked, it is equally harmless with the air-slacked lime. Without 
doubt it is an advantage to use the two alkaline earths together, if proper precautions are 
observed ; for magnesia seems to be as essential to the composition of many grains as lime, 
and may undoubtedly replace it when the lime is wanting. 
In the western counties, we pass from the Hydraulic or Magnesian limestones to the 
Onondaga limestone i the reason of this has been already explained. This limestone is a 
hard gray crystalline rock below, but passes upward into a dark shaly cherty rock, which 
is usually described under the name of Corniferous limestone. It extends from the Hudson 
river to Blackrock on Lake Erie, forming a belt from three to six miles wide. 
* Jackson’s analysis of the Ulster county cement stone, in the Proceedings of the American Geologists and Natu¬ 
ralists. 
35' 
