86 GEOLOGICAL SURVEY OF WISCONSIN. 



ical evidence, that the formation under consideration is the Water-lime 

 group of the Lower Helderberg, predicted from the lithological char- 

 acters of the rock, that the region would prove rich in hydraulic 

 cement. He did not then know that any discovery of the valuable 

 commercial properties of the rock had been made. An analysis of 

 specimens furnished Prof. Gustavus Bode, chemist of the survey, con- 

 firmed the conclusion and the prediction. The state of "Wisconsin 

 may be congratulated in a discovery that will add greatly to her re- 

 sources, to her industry and to her commerce. 



In the meantime, Mr. D. J. Whittemore, E. C., chief engineer of 

 the Chicago, Milwaukee and St. Paul Railway, a well known Wiscon- 

 sin scientist, had made a long series of careful experiments to test the 

 commercial value of the cement rock found in the Water-lime forma- 

 tion under consideration. He has demonstrated that it produces a 

 cement of better quality, consequently of higher value, than any 

 cement now produced, either in America or Europe, except the Port- 

 land., 



The following resume of the results of his experiments has been 

 kindly furnished by Mr. Whitteinore himself: 



MILWAUKEE, December 23, 1875. 

 DR. 0. "W. WIGHT, State Geologist of Wisconsin : 



MY DEAK SIR: In compliance with your request, I herewith make a condensed state- 

 ment of the principal results attained in my experimental inquiry as to the value of 

 hydraulic cement, made from the recently discovered stone deposit in the vicinity of 

 Washington street bridge, near this city. 



For the purpose of comparison, I selected from very many samples of commercial 

 cements those that, after a few days 1 trial, gave indications of good quality; therefore, 

 you will bear in mind, that the average strength of the commercial cement experimented 

 upon by me, is considerably above the general average of the cements in our market. 

 In both manipulation and testing, I availed myself of every experiment that I could 

 well devise to secure uniform treatment throughout my inquiry. 



I converted the natural Milwaukee stone into a cement by the usual method of calcina- 

 tion and grinding, and experimented upon the product from single stones separately; 

 also upon the mixed products of two stones selected from widely separated localities of 

 the ledge, each submitted to varied degrees of torrification in the preparation, and all 

 gave very similar results. This determines quite conclusively that within the limits 

 hereinafter mentioned the deposit has a uniform character, a matter of much import- 

 ance in determining its value. 



My experimental tests were directed to detennining the following features, viz. : 



1st. To ascertain the tensile strength in pounds per square inch of mortar, composed 

 of equal weights of cement and sand, at the age of ninety days, the last eighty-nine in 

 water. 



2d. To ascertain the breaking strength of mortars of cement mixed with definite por- 

 tions of sand, moulded into bars one inch square, and resting on supports three inches 

 apart, and broken by application of weight in the middle. Age of mortars one hundred 

 days, the last ninety-nine in water. 



3d. To ascertain the crushing strength in pounds per square inch of mortars of 



