316 Afjricultiu^al Chemistry. 



That organic materials are jiarts or remains of plants and ani- 

 mals. 



Tiiat organic manures are such as contain parts of plants or 

 animals. 



That inorganic manures are vianures from ichich all parts or 

 remains of plants and animals are excluded. 



These doctrines were admitted as truths by all scientific men, 

 by all chemists, vegetable physiologists, botanists, and are still 

 regarded as true. 



How, then, did Mr. Lawes begin to raise doubts of the accu- 

 racy of my doctrines ? From what position did he endeavour 

 to persuade the farmer that the truths I had taught were errors ? 

 He did this in the simplest possible way. — (Journal, vol. viii. 

 p. 240.) 



" Organic manures are those which are capable of yielding to the 

 plant., by decoynposition or otherivise, organic matter. Carbon, hy- 

 drogen, oxygen, nitrogen. 



" Inorganic manures are those substances which contain the mine- 

 ral ingredients, of which the ashes of plants are found to consist." 



So that water (oxygen and hydrogen), ammonia and ammo- 

 niacal salts are, according to Mi'. Lawes, organic matters ! ! 



phosphorus (phosphoric acid), alkalies, earths, salts, and metals, all derived from 

 the soil." (Gregory's ' Outlines of Organic Chemistry,' 1843.) 



I have quoted this passage to show that in 1843, and indeed long prior to that 

 period, I had learned from Baron Liebig, and understood and taught precisely as 

 he does in the text, his doctrine of the food of plants. I must also express my 

 surprise that any one should not be aware that the atmosphere and all its consti- 

 tuents, including carbonic acid, water, and ammonia, are always regarded as 

 mineral substances, and, as such, have their place in every system of mineralogy. 

 The distinction made in the food of plants is not between inorganic and organic, 

 for the whole is inorganic or mineral, but between atmospheric (gaseous) and ter- 

 restrial (solid). The term organic is only with propriety applied to such manures 

 as contain parts of dead animals or plants. But even these, before they can serve 

 as food for plants, must take inorganic forms. 



It is true that chemists sometimes speak of the organic food of plants, meaning 

 thereby carbonic acid and ammonia. But this, which is not a strictly correct 

 mode of expression, has reference, not to the nntiwc of these substances, but to their 

 origin, which is generally, but not always, from tlie decomposition of organic sub- 

 stances. The more accurate term would be the ijascvis food of plants, synonymous 

 with atmospheric. It is well known that springs from great depths often contain 

 both ammonia and carbonic acid, and that these substances are also poured into 

 the air from volcanic sources, both active and extinct. To such supplies the term 

 organic could not with propriety be applied, any more than to the carbonic acid 

 and ammonia on which the first created plants must have fed. The passages 

 above quoted from my ' Outlines ' show plainly the opinions I have always held 

 on these points, and prove incontestably that, in speaking of ammonia as an inor- 

 ganic or mineral constituent of the food of plants. Baron Liebig, in his ' Principles,' 

 has not had recourse to a manoeuvre or ruse, but has simply stated the fact as it is 

 understood among chemists. The error is on the side of his opponents, who have 

 misapprehended the occasional use of the term organic, as applied to the gaseous 

 food of plants, and have not clearly imderstood the distinction between the terres- 

 trial and atmospheric food of vegetables. — W. G., Translator. 



