46 THE BOOK OF THE LANTERN. 



baryta would be restored to its former condition, ready 

 for a repetition of the action. It would thus seem that 

 there was at hand a process for obtaining from the atmo- 

 sphere an endless supply of its essence, so to speak. But 

 as we have before hinted, theory and practice are two 

 different things. The process would not work on a com- 

 mercial scale. All went well at first ; but for some reason 

 or other, the baryta lost its power of recovery, and would 

 not repeat its office of absorbing oxygen. 



" A few years ago, two of M. Boussingault's pupils, Messrs. 

 A. and L. Brin, resolved to carry through a series of ex- 

 periments to find out, if possible, why in this case, practice 

 would not endorse theory. They soon found that the reason 

 why the baryta lost its power of absorbing oxygen was due 

 to certain molecular changes, which ceased to occur if 

 the air supplied was absolutely free from impurities, and if 

 the heat employed for reducing the baryta to its first 

 condition were kept within certain limits. They further 

 found that the necessary temperature might be much 

 reduced if the material were heated in a partial vacuum. 

 Another advantage was found in supplying the air under 

 pressure, in which case the absorption of oxygen from 

 it was much increased. These new conditions were speedily 

 realised in apparatus which was erected in Paris, and which 

 for three years yielded oxygen of the purest description 

 without any renewal of the baryta with which the retorts 

 were charged at the commencement of operations ; and this 

 apparatus was exhibited at the Inventions Exhibition at 

 South Kensington a few years ago. 



" The process having thus been shown to be workable, the 

 inevitable Company was formed ; and oxygen can now be 



