268 Mr. White's Design for the New London Bridge, 



Specific Gi-avity, Sfc. of Cement. — Specific gravity of Roman 

 cement made up a Ion <r time was 1*16, which was also that 

 of mineral cement the same as the bricks were made of. 



100 parts of Roman cement stone absorb of water 15. 



100 parts of mineral cement absorb of water 17*6 to IBS. 



A cubic foot of Roman cement forms |rds of a foot of 

 stone, shrinking ^rd by its being mixed with water, of which 

 it takes 47 of its own weight. 



A bushel of mixture composed of 3 measures of cement 

 and 2 of sand forms 1 cubic foot of stone. 



A cubic foot of cement brick-work weighs 105 pounds. 



VII. Memorandum of an Experiment made by Mr. Southern, 

 November 12, 1800, 'with a close brick box made WiVA Parker's 

 a7id Wyatt's Cement. 

 The box is 5 inches square within, 17 inches long, and the 



brick-work round it 4^ inches simply joined. The valve, of ly^ 



Valve. 

 \ 1t\ diameter. 



inch diameter, was loaded with 58lbs. 

 3oz,, and a forcing-pump was em- 

 ployed to force water into the box till 

 the valve and its load were lifted, and 

 the water issued out. This pressure 

 is equal to a pillar of water of 120 feet 

 in height, and is equal to 2 tons upon 

 the inside surface of 5 inches wide, 

 and 17 inches long : 

 62 X 4^ = about 280 inches, equal to the square of the sec- 

 tion of the brick-work. 44,000lbs. -r- 280 = nearly to 16lbs. 

 per square inch. The box did not fail with this pressure, but 



Leatlier pipe to the forcing- 

 pump, which was 2 inches dia- 

 meter, exactly worked by a lever 

 of 5 to 1, which 42 lbs. forced 

 down pretty readily. 



the pipe which conducted the water to the box was forced out 



of the pipe. 



This 



