302 : The Atlantic 



of efficiently using such steam pressure as the boilers could safely gen- 

 erate. The first engines introduced steam on only one side of the pis- 

 ton, but John Watt in Scotland soon discovered that he could in- 

 crease the efficiency of his engine by introducing steam alternately on 

 both sides of the piston, thus creating the double-acting engine which 

 became the standard practice; but engines were still single cylinder 

 affairs that exhausted the steam before it had been fully utilized. 



As early as 1824 an American engineer by the name of John P. 

 Allaire recognized this defect and built up the first engine with two 

 cylinders, using the steam first in a high pressure cylinder and then 

 passing it to a larger low pressure cylinder before it was exhausted 

 to the condensers. While his engine was right in principle it was not 

 a great success because he could not get a sufficiently high pressure 

 out of his boilers. It was not until 1854 that John Elder of Birken- 

 head built the Brandon, the first eflfective double-expansion engine. 

 Up to this time coal consumption had been at the rate of four or five 

 pounds for each horsepower developed in the engine, but the record 

 in the Brandon was 3'/^ pounds per horsepower. Operation of this 

 vessel made it clear that a triple-expansion engine would be an 

 improvement on the two-cylinder engine, just as the two-cylinder 

 engine was an improvement over the old single cylinder; but it was 

 not until 1874 that the first triple-expansion engine was built and put 

 into the steamer Propontis. In the meantime in 1857 the Thetis had 

 been built, which demonstrated that boilers and cylinders could safely 

 carry a steam pressure of 115 pounds per square inch, and that under 

 these conditions it required a little less than two pounds of coal per 

 horsepower. Higher steam pressures were developed only after the 

 old-fashioned oblong boiler was replaced by the cylindrical boilers 

 in 1862. Also adding to the strength and efficiency of boilers was the 

 introduction of the water tube principle. The French Belleville was 

 developed between 1880 and 1889; the Scotch Yarrow in 1889. 



Another change that came in the 1850's related to the position or 

 structure of the steam engine. Naturally the designer of a vessel wishes 

 to keep the heavy weights of his mechanism set low in the hull to 

 insure a low center of gravity. This was particularly desirable in the 

 days of the large and cumbersone engines put in rather small 

 wooden hulls. Therefore, the early steam engines had the heavy cylin- 

 ders at the base of the engine with the pistons operating vertically 

 upwards, and the connecting rods and driving mechanism above 

 that. This was a perfectly satisfactory arrangement for driving paddle 

 wheels which had an axis that of necessity was elevated above the 



