Proceedings of the British Association, 285 



ground above the solid slate rock it was reduced to 9 inches. 

 Nothing can better prove the superiority of the principle of this 

 invention, of getting the momentum by a heavy weight moving with 

 small velocity over the same momentum, as got, on the old principle, 

 by a light weight moving with great velocity, than the state of 

 the heads of the piles as driven by each process. Dr. Greene drew 

 attention to a sketch of two heads of piles, one 56 feet long driven by 

 a monkey of 12 cwt., falling from a great height, and making only 

 one blow in five minutes, and requiring 20 hours to drive it ; this, 

 though protected by a hoop of iron, is so split and shattered on 

 the head, that it would require to be re-headed to drive it any 

 further. The other, although 66 feet long, was not even supported 

 by an iron hoop, and the head is as smooth as if it were dressed 

 off with a new plane. It was driven with a hammer 50 cwt. and 

 only 3 feet fall, making 70 blows a minute. 



Mr. Fairbairn read a communication on the subject of Railway 

 Gradients, — the object of which was to show the importance of 

 economizing the first cost of railways, by introducing steep gradients 

 in difficult districts, whereby the expenses attendant on tunnels, 

 viaducts, and lofty embankments, would be avoided ; whilst the 

 author showed that the desired speed might be obtained by increas- 

 ing the power of the locomotive. Originally, cylinders only of 10- 

 inch diameter had been used, but at the present time, the engines are 

 furnished with cylinders of 14, 16, and 18 inches diameter. The 

 maximum speed which had been originally calculated on, was 10 miles 

 per hour, whereas, at the present time, the ordinary speed on the 

 Great. Western, with first-class gradients, is 40 miles. The paper 

 was illustrated by many experiments which had recently been made 

 with regard to gradients on the Manchester and Leeds Railway. 



Mr. Whishaw confirmed these views by the results of practical 

 experiments to the extent of nearly 4,000 miles, on nearly all the 

 lines of British railways. — From the Athenaeum. 



