354 On Steam-Engines. [Nov. 



a memorial of the gratitude of the new world, for the services 

 he had rendered it. 



In Philadelphia, the saving in fuel by the substitution of one 

 of Evans's high pressure engines for the low pressure one pre- 

 viously employed, amounted to about 1250/. per annum. This 

 engine raises 20,000 tons (tonneaux) of water, about 98 feet in 

 height, every 24 hours, and consumes about 1535 cubic feet of 

 wood per diem. The prime cost of the machine was rather 

 more than 5000/. ; whereas, according to M. Marestier, a low 

 pressure engine, of equal power, would cost considerably more 

 than 8000/. 



Evans's engines work with a pressure of from eight to ten 

 atmospheres ; several of them have been constructed in Ame- 

 rica- and in 1814 the Congress of the United States extended 

 Mr. Evans's patent 10 years beyond the usual period, as an 

 acknowledgment, on the part of the republic, of the benefit his 

 invention has conferred on his country. A similar extension 

 was granted in England, to Messrs. Boulton and Watt, for 

 their condensing engines. 



" More lately Mr. Perkins, an American, well known by his 

 ingenious processes for employing steel plates instead of copper 

 in engraving, has surpassed all his predecessors by the boldness 

 of his conceptions. He employs, for his moving powers, steam 

 vuider a pressure of more than 30 atmospheres, and apparently 

 with great advantage. 



" With respect to economy of fuel, we must, therefore, con- 

 sider the high pressure engines, hitherto constructed, as not 

 having attained the maximum. The use of condensed steam is 

 yet in its infancy; and, notwithstanding the services it has 

 already rendered us, we must consider them as far below what 

 may still be expected, when we shall be more capable of avail- 

 ing* ourselves of the full benefit of its effects." 



Second Part. — Measures of Safety. 



Habit reconciles us to danger. Hundreds of sailors perish 

 annually by the power of the wind on the sails of our ships, and 

 we think nothing of it, because we are become familiar to that 

 mode of navigation. But if a steam-boat be blown up, or burnt, 

 the accident is reported in the public prints to every corner of 

 the world ; the alarm is given, and that is looked upon as the 

 most dangerous of all mechanical powers, which perhaps is the 

 least so in the common course of navigation, and especially on 

 nearing the land. 



But destruction in some shapes is more appalling to the ima- 

 gination than in others. Death from explosions, accompanied 

 with noise and confusion, seems more horrible than when it 

 comes in a more tranquil form ; and in all our discussions on 

 the relative dangers of different machines, we should divest 



