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THE POPULAR SCIENCE MONTHLY. 



to illustrate the superiority of Milwaukee cement, shows that the 

 strength of the Milwaukee was three hundred and eighty-two 

 pounds per square inch at thirty days, and only three hundred 

 and fifty pounds per square inch at sixty days. This hardly 

 proves either the superiority of Milwaukee, or that natural 



cement increases in strength with age ; and, as it is the average 

 of seventy-five specimens, would rather seem to disapprove the 

 points mentioned. It is true that briquettes made of the same 

 cement, at the same time, kept under the same conditions, and 

 broken at the same time, show a groat variation in tensile 



