COMPARATIVE VALUE OF VARIOUS KINDS OF STONE. 4 1 



Conway tubular bridges, when fears were entertained of the 

 security of the masonry to support, upon the given area, the 

 immense weight of the tubes, upwards of 1,500 tons, resting 

 on one side of the tower. To ascertain how far the material 

 (Angiesea limestone) was calculated to sustain this load, the 

 following experiments were instituted by Mr. Latimer Clarke. 

 " Results of experiments made with actual weight on the 

 materials used in the Britannia bridge, January, 1848. 



Brickwork. 



tt>j. per square 

 Inch. 



No. I. — 9in. cube of cemented brickwork (Nowell 

 and Co.), No. I (or best quality) weighing 

 54 lbs., set between deal boards. Crushed with 

 19 tons 18 cwt. 2 qrs. 22 lbs = 551.3 



No. 2. — 9in. cube of brickwork, No. 1 weighing 

 53 lbs., set in cement. Crushed with 22 tons 

 3 cwt. qr. 17 lbs = 612.7 



No. 3. — 9in. cube of brickwork, No. 3 weighing 

 52 lbs., set in cement. Crushed with 16 tons 

 8 cwt. 2 qrs. 8 lbs = 454.3 



No. 4. — 9Jin. brickwork, No. 4 weighing 55£ lbs., 

 set in cement. Crushed with 21 tons 14 cwt. 



1 qr. 17 lbs = 568.5 



No. 5. — 9in. brickwork, No. 4 weighing 54J lbs., 



set between boards. Crushed with 15 tons 



2 cwt. qr. 12 lbs = 417. 



Mean 521. 



Note. — The last three cubes of common brick continued 

 to support the weight, although cracked in all directions; they 

 fell to pieces when the load was removed. All the brickwork 

 began to show irregular cracks a considerable time before it 

 gave way. 



The average weight supported by these bricks was 33.5 



