WITH REFERENCE TO HORTICULTURE. 25 



Exhausting land of the manure which it contains by over-cropping, is 

 like depriving a commercial man of his capital. 



In consequence of the great value of manures in increasing the 

 amount of the produce of land, many ingenious persons have contrived 

 mixtures, which, in small bulk, they allege will produce extraordinary 

 effects ; and this idea seems to have been long since indulged by some 

 writers. Lord Kaimes, nearly a century ago, thought the time might 

 come when the quantity of manure requisite for an acre might be 

 carried in a man's coat-pocket ; a recent author speaks of " a quart of 

 spirit sufficient to manure an acre ;" and even Liebig says, that 

 " a time will come when fields will be manured with a solution of 

 glass (silicate of potash), with the ashes of burned straw, and with 

 salts of phosphoric acid prepared in chemical manufactories, exactly as 

 at present medicines are given for fever and goitre." (' Organic Che- 

 mistry,' p. 188.) To those who believe in the homeopathic hypothesis 

 of medicine such speculations will not appear unreasonable ; and 

 there may be some truth in them, on the supposition that 

 these small doses of spirit, or of silicate of potash, are to act as 

 stimulants to the organic matter already in the soil ; but to 

 ordinary apprehensions it seems difficult to conceive how bulk and 

 weight of produce can be raised without the application of a certain 

 degree of bulk of manure. Since the introduction of guano, and the 

 more general manufacture of artificial manures, in the shapes of phos- 

 phates, sulphates, &c., we have daily proofs, however, of what can be 

 eilV-cted by small quantities of concentrated manures. 



With the exception of such manufactured manures, easily applied 

 as to their bulk, but to be used careftilly and sparingly owing to their 

 strength, all the manures mentioned in this section are easily obtained 

 by the possessors of suburban gardens. Soot and ashes are produced on 

 their own premises ; compost may be formed by the mixture of various 

 articles collected or procured ; liquids abound, and have only to be 

 collected and properly fermented ; and street manure may in general 

 be purchased from the nearest town. It cannot be too strongly im- 

 pressed on the possessor of a country residence who wishes to make 

 the most of it, that no particle of organic matter, whether animal or 

 vegetable, and no drop of water, with whatever it may be discoloured, 

 ought to be left uncoliected or allowed to run to waste. 



CHAPTER III. 



THE ATMOSPHERE, CONSIDERED WITH REFERENCE TO 

 HORTICULTURE. 



THE atmosphere on every part of the globe consists of the same consti- 

 tuent parts, to wit, nitrogen 78 parts, oxygen 21 parts, and carbonic 

 acid gas and vapours of water about 2 parts. It likewise contains slight 

 traces of ammonia and other gases. Its main constituents are always 



