106 ON THE STEAM BOATS OF 



result, that a greater speed might be attained ia a given vessel by using steam expansively, 

 was Adam Hall, at that time the director of the workshops of the West Point Foundry As- 

 sociation. He, at all events, entered very fully into the practical investigation of this subject, 

 and drew up a paper exhibiting his views, which was communicated to the writer of this 

 essay. The same views had been previously exhibited theoretically by the writer in a public 

 course of lectures delivered in February and March, 1830. These were soon after made 

 public in a treatise on the steam engine, which it is believed had some influence in the im- 

 provements that have since been made in navigation by steam. It was therein demonstrated, 

 that the power of a given engine might be doubled by loading the safety valve with 5 7 IDS. per 

 square inch, and cutting off the steam when one-eighth of the cylinder had been filled, and a 

 saving of two-fifths of the fuel effected at the same time. 



In the subsequent improvements of which we shall hereafter speak, the excellent work- 

 manship of the West Point Foundry, with which, however, Mr. Hall ceased to be connected, 

 and the high scientific attainments of the Messrs. Kemble, its president and agent, had a very 

 important influence. 



While the contests of which we have spoken were going on, Stevens was busily engaged in 

 building a new steam boat, to which he gave the name of the ' North America.' As this vessel 

 embodied all the improvements either in the original structure, or derived from experience in 

 his former steam boat, we shall give a concise description of her form and arrangements. 

 The dimensions of the 'North America' were as follow : 



Beam ..... 30 feet. 

 Draught of water ... 5 feet. 



Diameter of water wheel . . 21 feet. 



Length of bucket . . .13 feet. 



Depth of ditto .... 2 feet, 6 inches. 



The engines were two in number, and with the boilers, were placed upon the wheel guards, 

 thus leaving the deck free from incumbrance from stem to stern. The cabins beneath could 

 also be opened, so as to afford a clear view from the sternpost to the cutwater. The engines 

 worked with beams, and had the following dimensions : 



Diameter .... 44-^ inches. 



Length of stroke ... 8 feet. 



Strokes per minute . . .24 



The steam was usually raised to a tension, over and above an atmosphere, of lOtbs. per inch, 

 and was cut off at half stroke. The velocity through the water, as ascertained from the 

 average of a great number of passages, was 19'8 feet per second, or about 13 1 English miles 

 per hour. The relative velocity of the outer circumference of the wheel was 6*6 feet per 

 second. 



Another vessel, intended for a different navigation, namely, that from New York to New- 

 port R. I., was built shortly after the ' North America,' and was considered as successful an 

 application, taking the difference of circumstances into account, as that steam boat. In this 

 navigation it is necessary not only to pass the wide and often stormy sestuary, known as Long 

 Island Sound, but to enter the open ocean. It was therefore considered expedient to sacrifice 

 speed, for the purpose of rendering the vessel more fit for the navigation of agitated and tem- 

 pestuous waters. 



