The Progress of Scientific Agriculture. 425 



liad notliing mncli to record which woukl have lod any one to 

 expect that the chemist was soon to prove the farmer's best 

 friend. But we were able to show that his face was at length 

 set in the right direction; and that, though his many failures 

 had disgusted the men of practice, a few successes might easily 

 produce a revulsion of feeling in his favour. As early as 1770 

 the scientific world appeared uneasy and dissatisfied, as 

 though some occult influence was at work to force men for- 

 ward in the path of research. A faint perception was dawn- 

 ing upon their faculties that what they breathed could be 

 made to render up some great secret of nature, if only they 

 persevered in its analysis. Nobody continued to imagine that 

 when he grasped at the air his fingers closed over nothing at 

 all.^ In fact, the whole attention of the Royal Society was 

 now concentrated on the discovery of what the component 

 parts of the atmosphere might be. Priestley gained the gold 

 medal of the Society in 1773 for his Observations on the Varia- 

 tions of Air^ and Sir John Pringle, the learned President, de- 

 voted his ii] augural address to an historical review of the same 

 subject. He traced the progress of research from the time of 

 Galileo to the latest date. To Bacon he ascribed the discovery 

 of the so-called artificial air, to Newton of permanent air 

 arising from fixed bodies by heat and fermentation, to Brown- 

 ing of the quality of mephitic air, to Black of fixed air, and 

 to Cavendish of inflammable air. Turning lastly to Priestley's 

 prize essay on the same subject, he proceeded to point out 

 certain facts so intimately connected with oxygen that its 

 discovery trembled in the balance. He showed how the small 

 flame of an ordinary candle consumes^ as it was called, about 

 a gallon of air per minute, and he demanded of his audience 

 an explanation of the change made in the atmosphere by this 

 process. The next step was for Priestley to discover some 



* Men little thought that slightly over a ceuturj' afterwards air in 

 liquid shape would be visible to the naked ej-e. Could some old alchemist 

 but rise again he would be horrified to learn that the Goldsmith's Com- 

 pany, in whose industry he had been specially interested, was apparently 

 wasting its time and wealth in promoting, not the manufacture of gold, 

 but the liquefaction of valueless atmospheric gases. 



