402 



GEOLOGY OF EASTERN WISCONSIN. 



tained from the average of separate tests of two samples taken from 

 widely different parts of the outcrop on the Milwaukee river, and cal- 

 cined, one four, and the other three hours, and from a mixture of 

 these calcined for two and a half, three, three and a half, four, and four 

 and a half hours, respectively. The results indicate a convenient lat- 

 itude in calcination, which is an important consideration in securing 

 a uniformly reliable commercial product. 



To ascertain the breaking stength of the cement, rectangular bars 

 one inch square, in cross section, and four inches long, were prepared, 

 from the several samples tested, in a precisely similar manner, and al- 

 lowed to set under an end pressure of 32 pounds; when they were 

 removed and kept one day in air and ninety-nine in water. They 

 were then broken by resting them upon supports four inches apart 

 and applying weight gradually at the center. The results are given in 

 the following table: 



BREAKING STRENGTH OF CEMENT MORTARS. 



From the above, it will be seen that the average breaking strength 

 of the Milwaukee cement is 16 per cent, higher than the best result 

 obtained from the six commercial samples tested, when the propor- 

 tions were two of cement to one of sand, and 22 per cent, when the 

 proportions were one of cement to two of sand. The average of the 

 Milwaukee cement exceeds the average of the commercial cements by 

 56 per cent. That this difference is not due to inferiority in the com- 

 mercial cements used by Mr. "Whittemore appears from a comparison 

 with the results of tests made by Edward Yardley, C. E., reported in 

 the transactions of the American Society of Civil Engineers for 1872, 

 and given in the table above. Mr. Yardley's specimens were of sim- 



