PROGRESS OF FARMING. 53 



be as well established in nature as that 4 is the square of 2 in 

 numbers. The doctrine was more than 2,000 years old, and 

 found in the creed of every naturalist who treated of the 

 atmosphere. 



There are those now living who were present at the experi- 

 ments of Professor Black, of Edinburg, upon lime and char- 

 coal, and saw the processes by which the air, then called fixed 

 air, was brought out and shown to be a permanently elastic 

 fluid, and in connection with other airs, went to make up the 

 atmosphere. Thus the notions, — that the air was a simple and 

 the only fluid permanently elastic, although they were old as 

 the world, and had received the forms and sanctions of a 

 scientific proposition, — were exploded in an hour. Experiments, 

 suggested by an acquaintance with the constituents of vege- 

 tables, their composition and organs of growth, proved that the 

 aeriform state of carbon, and other constituent substances, was 

 one of the conditions of vegetation. Multiplied experiments 

 wrought multiplied revelations and revolutions in practice. 

 The gas family became numerous, respectable, and very useful. 

 Fertilizing substances innumerable were found readily suscept- 

 ible of conversion to that form and many unavailable in any 

 other. 



One discovery, where the relations are many and involved, 

 always has wrapped up in it the germs of a thousand more, and 

 agriculture is gathering the harvests that come of them. The 

 relative partialities, which the material elements have for each 

 other, and the strength of those partialities, are not among the 

 small discoveries of modern naturalists. They have intimate 

 relations to health, as well as production. Nitrogen, fatal 

 when free, entering largely into vegetation at maturing ; 

 ammonia, volatile and offensive, but without a peer among 

 the fertilizers, if the books tell the truth ; can through their 

 affinities, be gathered, stored, and kept for use, by gypsum, 

 muck, and other very common substances, which absorb and 

 retain them. 



These mutual affinities cannot be overvalued. They are as 

 available for life and health as for fertility. They do the 

 unclean work of scavengers — purify our surroundings — catch 

 and fix the exhalations — offensive and pestiferous, unavoidably 

 rising from the precincts of the mansion and yard, and turn 



