[ 264 ] 



XXXVIII. Papers relating to a Design for the Neto Lotidon 

 Bridge, on the Principle of Cement itious Architecture: — ex- 

 hibited to the Committee of the House of Commons, on the 

 1 Uh of April ] 823. By John White, Esq^. 



[Continued from p, 194.] 



VI. To John Wiite, Esq. 

 My dear Sir, — 

 T HEREWITH send you the papers I mentioned, which 

 -■■ I shall be obliged to you to return at your convenience, 

 and I wish you may find them of any use in your new project. 

 It would have given me pleasure to have had an opportunity 

 of conversing with you on the subject of cement previous to 

 your attendance on the Committee ; but I am on the Grand 

 Jury this week, and cannot get excused. 



I beg leave to offer my best wishes for your success; and am. 



Dear Sir, very faithfully yours, 

 Stamford-street, April 7, 1823. James Wyatt. 



Experiments for ascertaining the Strength of Cements. 



For making these experiments, a wooden mould was made, 

 20 inches long, 1 inch wide, and 1 inch deep.- for the purpose 

 of forming the cement into sticks or bars, all of which were 

 made under the same circumstances, except when otherwise 

 mentioned. The cement was found to set in 6^ minutes, and 

 the quantity required for making a bar of the above dimen- 

 sions was 1 5'6 ounces, taking also 7'3 ounces of water to make 

 it moderately stiff. 



On the 10th of October, 1811, a number of bars were made, 

 which were disposed of as follows: — 



1st. Some were left in an airy room without being touched 

 afterwards. 



2nd. Others were laid down in a spout, and were occasion- 

 ally wetted by the rain. 



3rd. Others were put at the bottom of a cistern, and con- 

 stantly kept covered by water. 



These three dispositions of the bars were intended to show 

 the difference or effect of having them kept constantly dry, 

 occasionally wet and dry, and constantly wet. The method 

 of trying the strength was by seeing what weight it required 

 to break the bars when suspended at one inch from the ful- 

 crum, which was accurately ascertained by a machine made 

 for the purpose. 



On the IGtli of October (the bars being six days old), the 

 26th of Novembei', 1811, 24th of January, and 15th of April, 



1812, 



