72 On the Production of Steam from heated Iron. 



become attached and finally disappear, amidst a rapid ebullition and 

 a violent hissing noise. 



In the use of his generators, somtimes at the temperature of red- 

 ness, Mr. Perkins had occasion to notice the fact above described, 

 and to observe that the repulsion, between the metal and the water, 

 sometimes becomes intense, amounting to a force greater than that of 

 the elasticity of the steam, and that a small pipe heated red hot, might 

 become entirely choked up, so to speak, with caloric, and incapable 

 of transmitting any water or steam. 



It may also be mentioned, that Klaproth has performed some ex- 

 periments on a small scale, illustrative of one part of the subject now 

 under consideration. But they seem to have given rise to some 

 erroneous deductions in regard to the action of metal. It appears to 

 have been Inferred, that, as in cooling his spoon down from a white 

 to a black heat, he passed from the time of AO" to O''' in the evapora- 

 tion of six drops, — he had actually arrived at a point where the action 

 of metal upon water would be instantaneous. 



From his experiments, and those of Perkins, it has likewise been 

 inferred that the point of incandescence is that from which the repul- 

 sion of water from the surface of metal commences ; and that above 

 redness, the augmentation of temperature is always attended by a cor- 

 responding diminution in the rapidity of evaporation. An opportunity 

 will perhaps be embraced in a future paper to recur to these opinions. 



The mode of performing the first of the following courses of ex- 

 periments, was by procuring a basin of wrought iron about eight 

 inches broad, one inch and three fourths deep at the center, and one 

 fourth of an inch thick, made from a piece of rolled iron, and weigh- 

 ing three pounds and a half. This was heated, either over a spirit 

 lamp, with an argand burner, in a stove of anthracite, capable of 

 maintaining a heat near whiteness, or at a forge fire, urged by a pow- 

 erful bellows. When deemed sufficiently hot, it was withdrawn from 

 the fire, and care being taken that no dust or ashes adhered to the 

 surface, a measured portion of water was laid upon the center, the 

 time from the moment it struck the metal till the last drop dis- 

 appeared being carefully noted from an accurate time keeper, and 

 recorded by an assistant. The temperature of the water was marked 

 by a good thermometer, or was kept boiling by remaining constantly 

 over the fire during a whole series. The trials were continued as 

 long as the metal remained hot enough to produce vapor of atmos- 

 phoric elasticity. The proceeding has rendered it highly probable, 

 that the rate of cooling after the period of most rapid action has 



