No. 275.] 
S3 
It should be observed that a great improvement has been introduced 
into the process of burning lime, which consists in the use of refuse 
screenings or dust of anthracite for fuel, instead of wood, and the em- 
ployment of a perpetual kiln. The coal dust is said to have cost $1 .75 
per ton in the city of New-York, while from fifty to seventy-five cents 
per ton were paid for its transportation to Thomason. 
Here, then, we have the singular fact that fuel is transported from 
the city of New- York to Thomason, and the lime procured by its 
agency again transported to the city. Now, the lime thus obtained 
must be greatly superior to that which is produced from our limestones, 
or else our citizens have been strangely neglectful of their interest in 
this respect. I have reason to believe that the counties of Westches- 
ter, Orange and Dutchess, contain limestones which would yield lime 
equal to any elsewhere manufactured. And with the improvements 
already introduced into our limekilns, as well as in those of Maine, 
one would suppose that our lime could be afforded at a much cheaper 
rate in the city of New- York, than that which is transported from a 
distant part of the United States. This subject commends itself to the 
enterprise of our fellow-citizens. 
As my object is to notice the useful minerals of the State, I shall 
proceed to offer a few remarks upon a subject closely allied to the above, 
and the importance of which will, I think, be generally acknowledged. 
It is 
The Hydraulic, or Water Limestones. 
32. It is well known that the lime obtained by the calcination or 
burning of the different kinds of limestone, differs greatly in its pro- 
perties. When the limestone is pure, the resulting lime is also of uni- 
form purity. Upon the addition of water to such lime a high degree 
of heat is produced, its bulk is greatly increased, and it at length falls 
to powder. This powder, when mixed with water, and a due propor- 
tion of sand, and afterwards exposed to the air, gradually acquires a 
stony hardness; but this result is not produced when the mixture is 
submitted to the action of water. Now these are designated by the 
name of air limes, and their relative value depends in some measure 
upon the kind of limestone, and the particular mode of calcination. 
But certain impure limestones when subjected to calcination afford 
limes which, while they do not undergo much change by simple expo- 
sure to the air, do not slake when moistened with water, but when 
reduced to powder, absorb this liquid without producing much increase 
