184 M. F. C. Henrici on the Action of Solid Bodies 



vessel In such case, in addition to the attraction between the 

 liquid and the air or gas, there is also an attraction between 

 both of these and the solid sides ; and it is a question which of 

 these two attractions will prevail. There are three cases to be 

 considered : — 



1. The attraction between a liquid and air or gas has the pre- 

 ponderance; m this case the solid sides produce no chance, and 

 there is no separation of gas. 



2 The attraction between the solid and the gas has the pre- 

 ponderance; m such case gas attaches itself to the solid, but 

 does not escape. 



3. The attraction between the solid and the liquid has the 

 preponderance, in which case there is a condensation of cas on 

 the solid surfaces, and, if the liquid is sufficiently supersatu- 

 rated, an escape of gas (the quantity depending on circumstances). 

 I he last case applies to Mr. Tomlinson's experiments, and also 

 to my own. fhe first condition in such an inquiry is doubtless 

 the most perfect cleanliness of the solid surfaces employed; for 

 with unclean surfaces definite results cannot be obtained* I 

 have adopted the following method for obtaining clean surfaces— 

 namely rubbing them with fine pumice-stone powder sprinkled 

 on soft leather. Surfaces so cleaned are well adapted to galvanic 

 experiments ; and their purity may be tested by the facility with 

 which water wets them. The solids used were metal/glass 

 and bone : the supersaturated liquid, to begin with the simplest! 

 was freshly drawn spring- water in small cylindrical glasses^ and 

 also ,n ordinary test-glasses. The observations were assisted bv 

 a double convex lens. The first experiments were with newly 

 cleaned wires of different thicknesses of platinum, silver, brass, 

 copper, plated copper, zinc, and steel, a strip of platinum, glass 

 and bone rods. These were usually attached to a cork, and so 

 sunk in the water to the depth of about two inches. No sooner 

 were the solids in contact with the water, than they, as well as the 

 side of the glass, were immediately dotted over with minute air- 

 bubbles, which constantly increased in number and size until after 

 some time, the surfaces were more or less covered with them oc- 

 casionally quitting hold and ascending. No difference of action 

 worth mentioning was to be observed between the different solids. 

 With h.ghly impregnated water, the bubbles reappeared more 

 or less numerously next day on immersing the solids. These re- 

 sults were obtained, however often the experiments were repeated. 

 My next experiments were with water supersaturated with 

 carbonic acid. The gas was generated bv means of common 

 effervescing powders, which enabled me to impregnate the water 

 * I have not made use of the terms " active" and « passive » since thev 

 are calculated to excite false ideas as to the mode of action * 



