Experimental Inquiries respecting Heat and Vapor. 307 



At temperatures considerably below that of most rapid vapori- 

 zation, there was constantly exhibited, in the various series of experi- 

 ments, a decided tendency in the water to adhere to the metallic 

 surface, and when by contact with a given portion of surface, and by 

 receiving and rendering latent in vapor, the heat which the latter had 

 possessed, the temperature of that portion was somewhat reduced, 

 the stratum of water was observed to glide away to other, hotter 

 parts of the surface, even against the force of gravity. 



This effect was observable in the cylinders with which the second 

 course on variable rapidity, was performed. Towards the conclu- 

 sion of each series, the water, after ceasing to boil in the bottom of 

 the cylindrical cavity, ascended in many instances quite to the top of 

 the cylinder, and even spread outward on all sides wherever it met 

 with a higher temperature than 212°. 



The same phenomenon was noticed in the basin already described, 

 and in the bar above mentioned. To make this effect the more dis- 

 tinct, a broad shallow pan of extremely thin iron, commonly called 

 by the tin plate workers, " black tin," was procured. In the centre 

 of this, a slight elevation, about one tenth of an inch high, was made, 

 with a corresponding cavity on the under side, or bottom of the pan.. 



A lamp being applied beneath the elevated part, the iron soon ob- 

 tained a dull red heat in the dark. Water was then laid upon the 

 basin so as to surround completely the centre, and form a sort of 

 island of heated surface. As the heat extended by degrees, and 

 reached the line of water, the latter was observed to start upwards 

 from its line, and moisten a portion of the surface not before wetted. 



By agitating the water with a hair pencil, and creating a wave 

 towards the centre, the line of vaporization became distinct. By 

 raising the waves still higher, that of repulsion was manifest, and by 

 causing a surge high enough to break quite over the insulated eleva- 

 tion, the alternate attractions and repulsions were seen in the drops 

 and masses which, having been driven forcibly beyond the first line 

 of vaporization, or that which they encountered on their ascent, were 

 subsequently rolled quite over the centre of the elevated embossment, 

 but arrested with great promptitude as they rolled down and reached 

 the line of vaporization on the opposite side. 



3. In order to ascertain the influence of certain lubrications in re- 

 ducing the rapidity, I placed the bar over a spirit lamp in such a 

 manner as to bring two of the mercurial reservoirs, and their adjacent 

 cups at equal distances from the centre of flame. Having allowed 



