394 



Foreign and Miscellaneous Intelligence. 



the scale-beam, and the water and vessel raised to 212 by heaters. 

 On making the experiments, the hot metal was introduced either at 

 once or more gradually, covered over with a perforated cover, and 

 the metal always withdrawn upon the cessation of ebullition ; the 

 loss of weight was then ascertained. As it was difficult to ascertain 

 temperatures above the boiling point of mercury, a barely red heat, 

 in daylight was chosen as a standard of comparison between the 

 different metals and different masses of the same metal ; and as it is 

 probable that the heated parts of boilers are seldom raised above a 

 dull red heat, it was thought that, for practical as well as theoretical 

 purposes, that point would be most interesting and important. The 

 experiments to determine the period of greatest activity show that, 

 just below the point of visible redness in daylight, the greatest quan- 

 tity of steam is generated in a given number of instants; such, at 

 least, is the case when the experiment is performed under ordinary 

 atmospheric pressure, and this point, therefore, has been termed the 

 comparable temperature. 



The following is a table of experiments with rolled iron boiler- 

 plate, 25J inches long by 7J broad and -j^ths thick, exposing 395 

 square inches of surface, and rolled into an open coil. The water 

 was at 212, the barometer at 29.9 inches: the room was from 80 

 to 85. 



The coincidence of the second, third, fourth, and fifth experiments 

 is remarkable, and proves that, at the temperature of comparison, 

 9 Ibs. of wrought-iron will generate 1 Ib. of steam under atmospheric 

 pressure. In after experiments it was found that, but for the caution 

 taken to avoid waste and error, this effect might have been produced 

 in 25 or 30 seconds instead of the times noted. 



A second series of experiments were then made with wrought- 

 iron cylinders 6 inches long, 1 . 7 in diameter, having a surface of 

 38 square inches, including the hook ; the water being, as before, 

 at 212. 



