MECHANICS AND USEFUL ARTS. 31 



the engines and boilers, to be subsequently isolated for a space of 

 three or lour seconds at a time, within a cylinder lagged, it is true, 

 at the sides, but wholly exposed to the atmosphere at the ends. The 

 cylinder was three feet in diameter, the area of each lid was over 

 seven square feet. It requires no very abstruse calculation to point 

 out the value of this area as a refrigerator during each tedious stroke. 

 Then we have the* valve chests and nozzles all aiding the same work. 

 Kor is this all. Mr. Isherwood, on his own showing, proves that the 

 loss due to clearance and nozzle space in the Michigan's engine, 

 amounted to a positive reduction of average pressure equal to 12 per 

 eeiit when the steam was cut off at one-sixth of the stroke, and to 

 nearly eight per cent when the cut-off took place at one-fourth of the 

 stroke. Some men are mentally so constituted that they only regard 

 any fact from one point of view. Instead of gathering from his ex- 

 perience that it was advisable that clearance of all kinds should be 

 reduced to a lower limit than that found in the particular engine ex- 

 perimented on, Mr. Isherwood, with a strange perversity, takes this 

 very loss of pressure as evidence that expansion is wasteful in prac- 

 tice and should not be employed. Our readers can form their own 

 estimate of the value of conclusions so arrived at. 



It is doubtful if the history of nations can show a more astounding 

 instance of folly in a case where the safety of the country was involved, 

 and that country actually at war, than that presented by the recent 

 proceeding of the Bureau of American Marine. On the evidence af- 

 forded by a series of experiments on a single engine in an old and 

 small steamer on an inland lake, conducted by four engineers, far re- 

 moved from supervision of any kind; the engine being, on the showing 

 of those most interested in proving the reverse, totally unsuited in 

 every respect for the application of expansion, the piston moving at 

 but 176 ft. per minute, and the steam not superheated in the slightest 

 degree, those in authority have determined, in their wisdom, to set 

 aside all the teaching of the last fifty years. They have wilfully shut 

 their eyes to the work of improvement going on daily in Kngland and 

 France, and have, with a temerity almost without parallel, staked the 

 future of a great navy and enormous sum of money on the truthfulness 

 of a single obscure experiment, bearing but a remote analogy in its 

 conditions to those under which steam should properly be employed. 

 It is as though the American engineering world had retrograded the 

 third part of a century. We shall expect, next, to have war steamers 

 denounced, and the old liner pronounced just the thing to defend the 

 interests of the people, or push on a war of aggression on distant 

 shores. 



Americans are very clever. They have taught us many new things. 

 This time, in the attempt to teach the world something new, they have 

 overshot the mark, and only repeated an old story in our ears, the 

 story of human lolly." From Ike. London Mechanic's Mayazinc, Jan. 

 1864. 



IMl'KOVKMKNTS IN STKAM IJOIJ.KltS. 



At the last meeting of the. British Association, Mr. Zerah Colburn, 

 the well-known American engineer, read a paper, giving a rcsumf of 

 the latest information and improvements concerning steam boilers ; 



