HYDRAULIC LIMESTONE. 79 



and a structure somewhat granular ; it contains organic remains, and occasionally nodules of 

 calcareous spar and sulphuret of zinc, with alternating layers or masses of hornstone. On 

 analyzing a fragment of this rock, I found it to consist of carbonate of lime, with a minute 

 portion of oxide of iron and bituminous matter, and with about eight per cent, of argil, or silica 

 and alumina. It does not contain even a trace of magnesia, although so closely associated 

 with the magnesian stratum above described. 



Water limestones occur in Albany County, in the Helderberg;* in Montgomery County, 

 about ten miles northwest of Schenectady, where it is of a drab colour, and resembles those 

 found fartiier west ; also in Herkimer County, some of which Mr. Vanuxem thinks would 

 aflbrd cements equal to any elsewhere made ; while according to the same geologist, they 

 arc found in immense strata in Oneida County. t 



Schoharie County. In the iirunediate vicinity of Schoharie Court-House is a stratum of 

 hydraulic limestone, which, according to my analysis, has the following composition, viz : 



Carbonic acid, 40 . .34 



Lime, 31 . 75 



Magnesia, 14.91 



Silica and alumina, ,,.. 11. 50 



Peroxide of iron, 1.50 



So that it does not differ essentially from the specimens obtained in Ulster county and else- 

 where. A remarkable fact connected with the water limestone of Schoharie, is the abundance 

 of sulphate of barytes and carbonate of strontian which it contains. These will be noticed in 

 the succeeding part of this work. 



Madison County. The hydraulic limestone of this county has long been in high repute. 

 One of the most important localities, and I believe one of the first, if not the very first, dis- 

 covered in the State, is situated about a mile and a half southwest of the village of Chitte- 

 nango. It has usually a drab colour, sometimes striped with reddish bands, a conchoidal 

 fracture, an earthy texture, and is covered by layers of the calciferous slate of Eaton. The 

 process of burning and grinding is similar to that heretofore described. When this cement 

 is used in the construction of works, it is mixed with from two to three parts of sand. 



It is computed that 100,000 bushels of hydraulic lime are annually sent from this town. 

 The average price is fourteen cents a bushel, which therefore yields a return of $14,000. 



The following are the results of two analyses of hydraulic limestone from this county ; the 

 first, by Mr. H. Seybcrt ;t the second, by myself: 



* According to an analysis of Prof. Eaton, wiiicii, liowevcr, ho did not deem veiy accurate, this limestone contains 25 per cent 

 carbonic acid, 26 lime, 28 silica, 18 alumina and magnesia, 1 iron and 2 water. Transactiom of the Albany Institute. Volume I. 

 Appendix, 53. 



i New-York Gcuhgical Repiirts, 1838. t Transactions of the American, Philosophical Society. New Series, 11.229. 



