THE OLD AND THE NEW. 45 



ing gold than of promoting those industries npon which the 

 production of food depends. Tliey manipulated the earthy 

 and metallic substances, in tlieir efforts to turn lead, iron, 

 &c., into gold, and utterly neglected to examine the proper- 

 ties of vegetable and animal substances. They knew noth- 

 ing of the constitution of air or water, or any gaseous body ; 

 and hence, if they had turned to the investigation of organic 

 structures, the obstacles in the way of success would have 

 been too formidable for them to have encountered. When 

 Dr. Priestley came upon the stage of action, his brilliant 

 discoveries and experiments brought in a new order of things. 

 Evelyn, Boyle, and specially Hales, had made some valuable 

 discoveries in regard to plants before Priestley's time ; but it 

 was he who laid the foundations of agricultural chemistry. 

 Dr. Black came to the aid of Priestley in his great discovery 

 of carbonic-acid gas ; and he soon pointed out that plants 

 had the property of purifying the air by decomposing the 

 carbonic acid, appropriating the carbon, and restoring back 

 to the atmosphere the oxygen, — a principle necessary to the 

 processes of combustion and respiration. 



These were great discoveries, and stimulated inquiry into 

 the mysteries of organic life to a degree never before 

 known. But, up to the close of the last century, nothing 

 of importance was known regarding the food of plants, the 

 chemistry of their growth, nourishment, &c. The coming- 

 in of the present century witnessed intense activity in this 

 field of research; and the labors of Humboldt, Berzelius, 

 Gay-Lussac, Lavoisier, Prout, and many others, served to 

 present a very accurate knowledge of the nature and com- 

 position of organic bodies. The dawn of a new science had 

 burst upon the world, that of vital chemistry ; and the en- 

 thusiasm and zeal awakened among investigators was very 

 great. 



The first chemist (if he may be called such) who ever 

 wrote upon agriculture, was one J. G. Wallerius, who, so 

 early as 1774, published a book on " The Cause of Fertility." 

 It abounds in crude speculations, and affords but little real 

 knowledge based upon experiment. Eleven years before, 

 another book upon agriculture appeared, called " The Ra- 

 tional Farmer," which is indeed a curiosity, and well worth 

 looking over iu this age of advanced scientific knowledge. 



