268 



SEPORT OF NATIONAL MUSEUM, 1899. 



burning the composition. The chemical composition of the samples 

 as given are as follows: 



An impure limestone, forming a portion of the water-lime group of 

 the Upper Silurian formations at Buffalo, New York, forms a "natural 

 cement" rock which is utilized in the manufacture of the so-called 

 Buffalo Portland cement.^ 



The so-called Rogendale cerroent is made from the tentaculite or 

 water limestones of the Lower Helderburg group as developed in 

 the township of Rosendale, Ulster County, New York. According 

 to Darton*^ there are two cement beds in the Rosendale- Whiteport 

 region, at Rosendale the lower bed or dark cement averaging some 

 21 feet in thickness and the upper or light cement 11 feet, with 14 

 to 16 feet of water-lime intervening. In the region just south of 

 Whiteport the upper white cement beds have a thickness of 12 feet 

 and the lower or gray cement of 18 feet, with 19 to 20 feet of water- 

 lime beds between them. The underlying formation is quartzite. 

 The method of mining the material from the two beds, as well as 

 their inclination to the horizon, is shown in Plate 13. (See Specimens, 

 Nos. 63062-63086, U. S.N.M., from Ulster, Onondaga, and Erie 

 Counties, New York; Nos. 63090-63099, U.S.N.M., Cumberland and 

 Hancock, Maryland; No. 53173, from Lisbon, Ohio, and No. 53193, 

 from Sandusk}^, Ohio). 



Roman cement. — The original Roman cement appears to have been 

 made from an admixture of volcanic ash or sand (pozzuolana, pepe- 

 rino, trass, etc.) and lime, the proportions varying almost indefinitely 

 according to the character of the ash. The English Roman cement is 

 made by calcining septarian nodules dredged up from the bottoms of 

 Chichester Harbor and off' the coast of Hampshire, and from similar 

 nodules obtained from the Whitby shale beds of the Lias formations 

 in Yorkshire and elsewhere. The following analysis of the cement 

 stone from Sheppcy, near South End, will serve to show the character 

 of the material: 



^Cement Rock and Gypsum Deposits in Buffalo. J. Pohlman. Transactions of the 

 American Institute of Mining Engineers, XVII, 1889, p. 250. 

 2 Report of the State Geologist of New York, 1, 1893. 



