Last of the Paddle Liners 8 7 



in describing in detail what compounding 

 is, beyond saying that the essence of the 

 compound system is to use steam as 

 expansively as possible. 



Still another very important factor may 

 be mentioned that greatly affected the 

 growing power of the steamship the 

 introduction of a much higher steam pres- 

 sure. If we remember that boilers were 

 worked at as low a pressure as 6 Ibs. in 

 the earliest marine engines, we shall appre- 

 ciate the extra power and efficiency which 

 was obtained when a pressure of 160 Ibs., 

 and even greater, was regularly used. 



What this really means is that when the 

 steam came to be used a second or third 

 time in compound working, there was not 

 only a. vast increase in power, but a very 

 substantial saving on the coal bill, as 

 much as 25 per cent being saved in many 

 cases where the same ship was converted 

 from simple to compound working. 



So far as I am able to trace, the first com- 

 pound engines were fitted to two paddle 



