HAMILTON CEMENT ROCKS. 



403 



ilar form, composition and age, but were made plastic like mason's 

 mortar, while Mr. Whittemore's were all made stiff. Making all due 

 allowance for this, it still appears evident that Mr. Whittemore used 

 a superior selection of commercial cements. 



For determining the crushing strength, cylinders of mortar having 

 a base area of one square inch, and a height of one inch, were formed 

 from the several cements, and kept under a pressure of 32 pounds 

 until set, when they were kept in a dry room one day, and then im- 

 mersed for 89 days in water, when they were crushed, several samples 

 of each being used. The following table gives the results obtained: 



CRUSHING STRENGTH, 

 In pounds per square inch, of cement mortars, 90 days old, the last 89 in ivater. 



By an inspection of the above table, it will be seen that in the 

 strength of the clear cement, the commercial articles Nos. 7 and 11 

 surpass the Wisconsin product, but as the admixture of sand is in- 

 creased, the relative superiority of the latter becomes very conspicu- 

 ous. It appears that the larger the proportion of sand, the greater 

 the relative value of the Milwaukee cement. Since cement is usually 

 used with at least an equal quantity of sand, the columns in the above 

 table that give the proportions of 1 to 1, 1 to 2, and 1 to 3, indicate 

 the practical value of the products examined, and they therefore are 

 combined in the sixth column of the table. The last column gives in 

 a more convenient form the value of the several cements for the pro- 



