502 The Storage of Farmyard Manure 



The second notable advance was made about 1800 by von Thaer^, 

 the most distinguished agricultural chemist of his day. It is true 

 that he was still adopting Columella's recommendations already given ; 

 but he made some experiments,^ — only on a very small scale, using a 

 few ounces of manure, and with the old analytical methods of dry 

 distillation, — which, he considered, showed the necessity of excluding 

 air from the heap : he supported, therefore, the practice known, but 

 not common, of sending bullocks or carts over the heap to compress 

 it, and then covering it with a layer of earth. Boussingault^, who took 

 many of his ideas from von Thaer, adopts this one in toto ; but he also 

 re-examined the Columella recommendations that von Thaer had ac- 

 cepted, and promptly dismisses the idea that various manures should 

 be kept separate. But Boussingault's great achievement was to 

 reveal the true nature of manure by demonstrating the connection 

 between food and dung, and he showed that the composition of the dung 

 was simply that of the litter + the food, less anything retained or 

 breathed out by the animal. Thus, when the necessary physiological 

 data were available, the composition could be calculated by simple 

 arithmetic. This constitutes the greatest advance of all for it afforded 

 the basis on which all modern work has since developed. 



We may now briefly summarise the results of the 50 years' work 

 which began with Young and ended with Boussingault : 



1. Farmyard manure represents the litter + that portion of the 

 food which the animal does not retain or breathe out ; its composition 

 is therefore directly related to that of the food (Boussingault, 1840). 



2. The manure gives the best results when it is used in its unaltered 

 state and without any preliminary rotting : the manure heap is, there- 

 fore, only a matter of convenience and not of necessity (Young). 



3. If a heap has to be made it must be done so as to exclude as 

 much air as possible (von Thaer, 1800). 



4. It must be protected from rain : if no cover is available a layer 

 of earth affords useful protection (Mortimer, 1707, but may be older). 



' A. von Thaer, OruiuJsdtze der rationellen Landwirfschaft, 1810, Bd. 2, pp. 87 et seq. 

 The experiments are described in a paper by Thaer and Einhof entitled "Versuche und 

 Beobachtimgen iiber die Excremente vom Hornvieh, und ihre Fanlniss," published in 

 Hermbstadt's Archiv der Agriculturchemie, 1804, 1, 255-304. Nothing illustrates more 

 vividly the enormous strides made by agricultural chemistry during the period 1804 to 

 1840 than a comparison between this and Boussingault's papers. 



* Economie Rurale. Boussingault thought that some of the nitrogen was actually 

 exhaled: it was not till physiologists had proved this not to be the case that the full 

 value of his work was appreciated, 



