138 Mr. C. Tomlinson on the so-called 



come in contact with them. In like manner a glass rod made 

 chemically clean will act differently from a rod that has been ex- 

 posed to the air : the latter is said to be in an " active" condi- 

 tion ; what then is the former ? Is it " inactive " because it does 

 not always do the work that is expected of it ? But it may do 

 other work, and prove itself a more efficient agent than the so- 

 called "active" rod. This is particularly the case with the in- 

 teresting experiments on the supersaturated solutions of gases 

 already referred to. But what are the facts ? A glass rod or 

 other solid body put into soda-water or Seltzer-water disengages 

 gas provided it has been previously exposed to the air, but not 

 otherwise. It loses this property if kept for some time in the 

 solution, or if previously immersed in water or heated, and hence 

 it has been concluded that it is not the solids that disengage the 

 gases, but the air in contact with them. It is assumed that a 

 solid, whatever its polish, " is covered with roughnesses that form 

 a sort of network of capillary conduits into which the surround- 

 ing gases penetrate and condense," and " the gas-bubbles thus 

 imprisoned become the centres to which pass those which are 

 dissolved." It is supposed that a lengthened immersion in water 

 or exposure to heat renders the solids "inactive" by removing 

 the air from their surface. 



It is with diffidence that I venture to cast a doubt upon a 

 theory supported as this is by ingenious reasoning and experi- 

 ments, and the applause of the scientific world; but as the only 

 object with which we cultivate science is, or ought to be, the 

 discovery of truth, so the earnest student will not the less wel- 

 come her, even though she be not smiling on his pet theory. 

 One of the best and wisest of French philosophers says, " II ne 

 faut pas juger de la nature selon nous, mais selon elle." 



When a bottle of soda-water is uncorked and poured into an 

 ordinary drinking-glass"*, after the brisk effervescence is over, 

 the sides and bottom of the glass are more or less covered with 

 bubbles of carbonic acid. If the glass were chemically clean, 

 these bubbles would form in much less quantity, or not at all. 



Exp, 1. Two test-glasses, A and B, were selected and wiped 

 out with a clean cloth. A was then filled with methylated 

 spirits of wine, and rinsed out with water to get rid of the adhe- 

 ring spirit. A bottle of soda-water was then uncorked and 

 gently poured into the two glasses. B was profusely covered 

 with gas-bubbles. Not a single gas-bubble was seen on the sur- 

 face of A. 



* In opening a bottle of soda-water there is generally a waste of liquid at 

 the moment the cork flies out, in consequence of the retroactive motion of 

 the bottle. This may be prevented (unless the liquid be very highl} charged 

 with gas) by resting the bottle firmly and upright on a solid support while 

 removing the cork. 



