42 MR. W. FAIRBAIRN ON THE 



tons per square foot, equal to a column 583.69 feet high, of 

 such brickwork. 



Sandstone. 



fibs, per square 

 inch. 



No. 6. — 3in. cube red sandstone, weighing 1 lb. 

 14g oz., set between boards (made quite dry by 

 being kept in an inhabited room). Crushed 



with 8 tons 4 cwt. qr. 19 lbs = 2043. 



No. 7. — 3in. cube sandstone, weighing 1 lb. 14 ozs., 

 set in cement (moderately damp). Crushed 



with 5 tons 3 cwt. 1 qr. i lb = 1285. 



No. 8. — 3in. sandstone, weighing 1 lb. 15 J ozs., set 

 in cement (made very wet). Crushed with 



4 tons 7 cwt. qr. 21 lbs = 1085. 



No. 9. — 6in. cube sandstone, weighing 18 lbs., set 

 in cement. Crushed with 63 tons 1 cwt. 2 qrs. 



6 lbs =3924.8 



No. 10. — 9 Jin. cube sandstone, weighing 58 J lbs., 

 set in cement (7 7 \ tons were placed upon this 

 without effect, = 2042 lbs. per square inch, 

 which was as much as the machine would carry) 



Mean 2185. 



All the sandstones gave way suddenly, and without any 

 revious cracking or warning. The 3in. cubes appeared of 

 ordinary description; the 6in. was fine grained, and appeared 

 tough and of superior quality. After fracture the upper part 

 generally retained the form of an inverted square pyramid 

 about 2 Jin. high and very symmetrical, the sides bulging 

 away in pieces all round. The average weight of this mate- 

 rial was 130 lbs. 10 ozs. per cube foot, or 17 feet per ton. 



The average weight required to crush this sandstone is 

 134 tons per square foot, equal to a column 2351 feet high of 

 such sandstone. 



