Proceedings of the British Association. 239 



munication in the French language, first proceeded to show that a 

 drop of water projected upon a red-hot plate does not touch it ; but 

 that a repulsive action is exerted between the plate and the fluid, which 

 keeps the latter in a state of rapid vibration. At a white heat, this 

 repulsion acts with the greatest energy, whilst it ceases, and the 

 ordinary process of evaporation takes place at a brown-red heat. The 

 temperature of the water whilst in the spheroidal state is found to be 

 only 96°, and this temperature is maintained so long as the heat of 

 the plate is kept up. To bring this water to the boiling point (to 

 212°), it is therefore necessary to cool the plate. These phenomena 

 are explained by M. Boutigny on the supposition that the sphere of 

 water has a perfect reflecting surface, and consequently that the heat 

 of the incandescent plate is reflected back upon it ; and some experi- 

 ments have been made, which show that this is the case, the plate 

 becoming visibly redder over those parts on which the vibrating glo- 

 bule played. Several experiments were made in proof of this necessary 

 cooling to produce ebullition. The red-hot plate, with its spheroidal 

 drop, was removed from the spirit-lamp, and after a minute or two, 

 the water began to boil, and was rapidly dissipated in steam. Am- 

 monia and ether were shown, although so exceedingly volatile, to act 

 in the same manner ; the ether, however, being decomposed whilst in 

 the vibratory condition, in the same manner as it is by the action of 

 platina wire, forming a peculiar acid. Iodine put upon the heated 

 plate became fluid, and revolved in the same manner as other fluids, 

 no vapours escaping whilst the high temperature of the metal was 

 maintained ; but when allowed to cool to the point of dull redness, 

 it was immediately dissipated in violet vapours. The nitrate of am- 

 monia fused on the glowing hot plate, and vibrated with great energy ; 

 but on cooling the capsule, the salt entered into vivid combustion. 

 The repulsive action was shown by plunging a lump of silver at a 

 glowing red heat into a glass of water. As long as its bright redness 

 was maintained, there was no ebullition ; but as it slowly cooled, 

 boiling took place. In this experiment, it appeared as if the glowing 

 metal formed around itself an atmosphere ; and the contiguous sur- 

 faces of the water appeared like a silvered plate. The application of 

 the principles involved in these phenomena to the tempering of 

 metals was then explained. If a metal to be tempered is in a highly 



