150 



periods per second should not exceed 9 

 centimeters, with a saturation of 7,000 

 C.G.S. units. 



Mr. A. A. Campbell Swinton said there 

 seemed to be an impression amongst 

 engineers generally, that very high-speed 

 machines like the Parsons must sacrifice 

 durability. At Sir "William Armstrong's 

 works at Newcastle there were three 

 Parsons machines, two of which ran at 

 about 9,000 revolutions per minute, and 

 the other at about 17,000. They had 

 been running for three years, and neither 

 the bearings nor the spindles had 

 appreciably worn away. He thought 

 that the brushes and the commutators 

 were the only parts which had been re- 

 newed. Of course the Parsons machine 

 was a special machine, and the bearings 

 were specially designed to suit the high 

 speed. The fact that high speed had 

 not received much attention was not the 

 fault of electricians, but of engineers. If 

 engineers had produced engines that 

 would run at these high speeds, no 

 doubt electricians would have produced 

 dynamos for them. 



