140 Mr. C. Tomlinson on the so-called 



Exp. 6. Iron-filings shaken up with spirits of wine, gently de- 

 posited on a fresh quantity of soda-water sank without liberating 

 any gas. 



But it will be said that the filings in exp. 5 were full of air, 

 which was absent in the filings used in exp. 6. Now let us see 

 whether air has really the function assigned to it of liberating 

 gases from their solutions. 



Among the apparatus of this College is a closed cylinder of 

 fine wire gauze 2J inches long and 2 inches in diameter. Attached 

 to the centre of one end is a wire stem 7 inches long, which is 

 used for a handle. By means of this piece of apparatus a beau- 

 tiful experiment on the adhesion of water to a solid is shown. 

 The cylinder can be completely filled with water and carried 

 about without its escaping. It is, however, necessary to the 

 success of this result that the wire cage be chemically clean ; 

 accordingly we are in the habit of washing it in a weak solution 

 of caustic potash before attempting to use it. 



Exp. 7 . The wire cage was washed in spirits of wine, then 

 plunged several times into clean water, and placed, empty but 

 wet, in soda-water. There was no escape of gas. The cage was 

 lowered to the bottom of the solution so as to have a mass of air 

 in the midst of it ; but still no escape of gas, except from that 

 portion of the wire handle that had not been dipped into the 

 spirit and was not chemically clean. Soda-water gradually filtered 

 into the cage,,which was taken out three-fourths full of liquid, from 

 which there was no escape of gas. It was repeatedly immersed 

 in the solution, and when at length it was taken out and shaken, 

 the stream of liquid falling into the liquid in the glass produced 

 a slight effervescence. 



I must claim for this experiment the conclusion that the pre- 

 sence of air is not concerned in liberating the gas from its 

 solution. 



Now let us see what is the action of the cage when not che- 

 mically clean. 



Exp. 8. About half a drop of oleic acid was rubbed between 

 the palms of the hands, and these were brought into contact with 

 the cage. No sooner did the cage touch the soda-water than 

 there was an audible boiling effervescence, which became more 

 abundant on lowering the cage ; even the sides and bottom of 

 the glass, which before were chemically clean and were quite 

 free from bubbles, became covered with large adhering bubbles. 



But the action of heat, it is said, renders solids inactive by 

 removing the gas from them by expansion. Of course, according 

 to my view, the action of flame is to burn off impurities and so 

 render the solid chemically clean. If the theory which I am 

 opposing be true, a body raised in any way to a high temperature 



