774 Transactions of the American Institute. 



Beton-Coignet, best 7>495 



Beton-Coignet, average 4 > 670 



Concrete, Ransome 6 > 720 



Frear Stone 4, 500 



Brick, first quality, hard 4> 368 



English Portland cement, consisting of 1 vol. sand and 1 vol. 



cement, age six months 3>455 



English Portland cement, same mixture, age 3 months. . . . 2? 518 



The strength of the Beton-Coignet was determined by Michelot, 

 that of Ransome's concrete by Ansted, the one of English Portland ■ 

 cement by Grant, and that of the other stones by General Gillmore. 



The principal business of the Union Stone Co. up to the present 

 time has been the manufacture of emery wheels. Regarding the 

 tensible strength of the material, General Gillmore says that it may 

 be inferred from the fact, that in the proof trials the wheels are 

 made to revolve with a velocity of from two to three miles per minute 

 at the circumference. They do not usually begin to break until a 

 velocity of from four to five miles per minute is attained. 



Durability. 



In order to test the durability of building materials under exposure 

 to the vicissitudes of the seasons, the so-called frost test, indicated by the 

 French chemist, M. Brard, is very generally followed. In this test the 

 crystallization of the sulphate of soda (Glauber salt) is substituted for 

 the freezing of water. The specimens of stone are immersed into a 

 saturated solution of this salt, and after being withdrawn are left to dry. 

 The solution is kept boiling for half an hour each time, and the test 

 is made daily for a week, when the specimen is weighed and the loss 

 determined. Dr. C. T. Jackson, one of the State assayers of Massa- 

 chusetts, has made these tests with the Sorel stone, and reports as 

 follows : 



" From this test it is evident that your stone will withstand the 

 action of frost more perfectly than any sandstone or ordinary building 

 stone, now in use. I see no reason why it will not stand as well as 

 granite." 



Dr. Ott doubted the reliability of this test, and, in support of his 

 view, read a passage from a work by Prof. Fuchs, written in 1829. 

 But, said he, whatever may be the case, it is a fact that, in Boston, 

 building blocks made of Sorel stone have resisted two winters, and at 

 the present time appear, it is said, harder and stronger than before 

 they were touched with frost. 



