428 
Agricultural Chemistry. 
" The view which assumes that the saline substances which manures con- 
tain, are their only really useful constituents, would lead to advising farmers 
to burn their manure heaps in order to diminish the carriage, always such an 
inconvenience and so costly. I question whether this advice would ever be 
followed. Moreover, careful observation has shown that the organic sub- 
stances in manure exert a very marked effect. Thirty square metres of in- 
fertile clay soil were manured with farm-yard manure, and yielded a very good 
crop of oats. By the side of this, on an equal surface, were spread the ashes 
(the salts therefore) of an equal quantity of the same manure ; by so doing 
the produce was not sensibly increased." — Economie Eurak, vol. ii. p. 81-2 
(Translated). 
Another able French writer, M. Puvis, in his ' Traite des 
Amendements,' says (we give the passages translated) — 
" Humus, in a soluble state, would be the peculiar food of jilants, and 
would, moreover, furnish tnem with an incessant supply of carbonic acid, as 
the illustrious chemist of Giesseu himself admits, though at the same time he 
calls in question the necessity of animal manures." — p. 423. 
" The illustrious chemist of Giessen, having formerly admitted, in common 
alike with practical men and theorists, that ammonia is an essential and ne- 
C(!ssary constituent of manure, novf regards it (ammonia) as one of the con- 
stitueut principles of atmospheric air, aud maintains that plants will derive it 
thence according to their requirements, as they do carbonic acid." — p. 623. 
" He then goes on to express a hope that the time may come when saline 
matters in small bulk will be substituted for animal manures." — p. 624. 
" In his new system he would almost exclude nitrogen, which however 
practical experience teaches us to look upon as one of the most active agents 
of production." — p. G24. 
" Since the chemist of Giessen, Liebig, has proposed to replace the manure 
heap by small quantities of saline substances, and has himself set the example 
of the sale of these substances, propositions for new manures have rained upon 
us in all parts of Europe ; in iVance, much more than elsewhere, manufac- 
turing processes have risen rrp in all directions, to replace stable and other 
powerful manures by substances either in powder or in the liquid state, of a 
bulk fifty or one hundred times less than even the smallest quantities of 
manures which experience had sanctioned. Since 1842 we may reckon eighty- 
six patents of inventions for new manures, aud all promise the highest produc- 
tiveness." — 1"). 627. 
" The chemist of Giessen has adopted the fundamental principle of the system 
of Duhamel, namely, that plants derive from the atmosphere all the volatile 
principles which enter into their composition ; but considering that plants also 
contain fixed mineral principles which are not found in the atmosphere, and 
that successive crops would soon deprive the land of these substances necessary 
to vegetable organization, he has thought it necessary to add to the system of 
Duhamel, as a necessary condition, that we must give to the soil the mineral 
substances according to the composition of the crop that we wish to produce. 
Convinced of the justice of his theory he thought to profit by it, and accord- 
ingly artificial manures modified to suit the nature of the soil, and the kind of 
crops, were sold under his name in Germany and England ; the name of the 
distinguished chemist ensuring in these two countries a great number of 
trials, to which nothing in general was wanting but success." — p. 632. 
" After the failures resulting from the use of the Liebig manures they were 
soon abandoned, and the analogous composts to which they had given rise, 
also quickly fell into discredit." — p. 635. 
In Germany, — numerous writers have told us how they under- 
