882 NEW YOEK STATE MUSEUM 



occurs Lecaiise of methods or materials used in tlie actual man- 

 ufacture of the cement, or, as seems certain in some cases, be- 

 cause of treatment after burning, it is a decided defect in the 

 cement, and is not guarded against by the present specifications. 

 The long time tests advocated above would go far toward pre- 

 venting the acceptance of such cements, but a more direct method 

 of attaining the same result would seem to be preferable. This 

 might be done by changing the last two paragraphs of § 35 of 

 the present specifications so as to read: 



Briquets composed of three parts by weight of standard crushed 

 quartz and one part of weight of Portland cement, mixed in the 

 same manner and kept seven days under the same conditions, 

 shall show a least average tensile strength of 125 lb per square 

 inch. 



Briquets of three parts by weight of standard crushed quartz 

 and one part by weight of Portland cement, mixed in the same 

 manner and kept 28 days under the same conditions, shall show 

 a least average tensile strength which shall be at least 50/^ greater 

 than that shown by briquets from the same lot, tested at seven 

 days, and shall in no case be less than 220 lb per square inch. 



Results of the tests 



The results obtained durins; the four vears noted have been 

 tabulated in the following pages. A few tests have been omitted, 

 where the circumstances seemed to render it advisable to take this 

 action. 



On pi. 1-12 are shown the average results obtained in the tests 

 for fineness, time of setting, and tensile strength, the cements 

 having been grouped according to locality. From these diagrams 

 it will be seen that the E'ew York Portlands have for three years 

 out of the four given the highest results for fineness; that in 

 tensile strength they are about on an equality with those manu- 

 factured in Pennsylvania, the product of both states averaging 

 lower than do the two E^ew Jersey brands; while the results 

 shown in the tests for time of setting are the most variable. 



