CHAPTEES ON THE CEMENT INDUSTEY 851 



are fullers' earth, kaolin and lime. Tliey are tlioronglily ground 

 and mixed together in suitable proportions by the Avet process, 

 although much less water is used than in the English works or in 

 those at Boulogne. The mixture when completed is in a rather 

 stiff semiliquid state. In this condition it is run out upon a floor 

 underlaid with warming flues, where it is dried to the stiff of 

 tempered brick clay. It is then passed through a brick machine, 

 and subsequently burnt in common continuous upright kilns with 

 anthracite coal. 



Specimens -of this cement have been tested several times by 

 the writer with excellent results. On the last occasion the method 

 adopted with the cements in the exhibition was stricth^ followed. 

 li inch cubes, seven days old, composed of equal parts of dry 

 €ement and sand, gave a' crushing strength of 3335 lb. per cube, 

 as an average of 20 trials, being a little higher than the best Port- 

 land cement exhibited, as shown by the table. 



Succeeding this, in point of date, was a small plant at Low 



Point, Dutchess co., erected by the engineer and contractor for 



the first Poughkeepsie bridge. Some cement was made here, 



and used in the tower foundations, but the failure of the bridge 



project also ended the cement experiments. 



Wallkill Portland cement co. 



During the winter of 1877-78 Messrs J. Gardner Sanderson 

 and T. T. Crane carried on a series of experiments at Croton on the 

 Hudson. A small upright kiln was in use, with a Bogardus mill, 

 and the power which, during the summer, was used in brick- 

 making. These experiments, and the analysis of a large number 

 of specimens of possible materials convinced the experimenters 

 that the Hudson river limestones generally contained too high 

 a percentage of magnesium carbonate, and the clays too much 

 free sand, to be suitable ingredients of a Portland cement. Cer- 

 tain strata of limestone, however, belonging to the Helderberg 

 ;groups'^ (the outcrops of which extend approximately north and 



1 Limestone from the same horizon is now being used in the manufacture 

 of Portland cement by two companies, the Catskill cement co. and Alsen'a 

 American Portland cement CO., both plants being situated a short distance 

 south of Catskill. 



