248 



Mr. Ewart on the Phcenomena attendins. 



ticity of the steam was equal to sixty pounds (including the at- 

 mosphere) on the square inch, and, consequently, the interior 

 temperature about 290° of Fahrenheit, I applied the bulb of 

 a thermometer close to the opening of the safety-valve, while 

 the steam issued from it in great quantity, and it stood steadily 

 at 160°. The engine being in motion, and the steam, after 

 having passed through the cylinder, escaping to the atmo- 

 sphere by a perpendicular pipe four inches diameter, and five 

 feet in height, I applied a thermometer to the steam as it issued 

 from the top of that pipe, and found the temperature to be 212°. 

 Finding the temperature of the issuing steam only 160° at 

 the safety-valve, close to the boiler, and 212° after it had passed 

 to the distance of five feet from the boiler, I constructed 

 an apparatus (tig. 1.) for the purpose of ascertaining whether, 

 under certain circumstances, the temperature of the steam 

 increases after it has issued from the boiler. I had an oppor- 

 tunity (in March 1823) of applying this apparatus to the high- 

 pressure steam-boiler of Mr. Philip Taylor, at Bromley, near 

 London. A is an iron pipe of three quarters of an inch bore, 



Fig.l. 



212* 



232° 



connected with the boiler, and terminated by a stop-cock B, 

 the area of the opening of which was the same as that of the 

 pipe. The end of a copper tube C, two inches diameter and 

 sixteen inches long, was screwed to the cock B, so as to be 

 steam-tight. To this tube was adapted a thermometer D, so 

 that the bulb stood directly opposite the centre of the open- 

 ing of the cock B, and at the distance of an inch and a half 

 from it. The opening in the side of the copper tube, through 

 which the stem of the thermometer passed, was made steam- 

 tight. Another thermometer E was fixed in the same man- 

 ner, near the extreme end of the copper tube, which end was 

 quite open to the atmosphere. The elasticity of the steam in 

 the boiler being equal to fifty-eight pounds, including the at- 

 mosphere, on the square inch (the internal temperature con- 

 sequently about 285°), and the cock B fully open, the ther- 

 mometer D stood at 212°; while E stood at 232°, sliowing an 



increase 



