528 Agricultural Possibilities. [September, 
furnished by the soil. The ammonia and the oxides of nitro- 
gen present in rain-water are obviously insufficient to account 
for such a surplus. But, on the other hand, repeated attempts 
have been made to verify experimentally this supposed assi- 
milation of free nitrogen by plants, and the result has been 
in every case negative. Some undetected source of error 
must therefore have been present, either in the experiments 
of M. Ville or in those of other chemists of eminence, many 
of whom investigated the question without any reference to 
his views. 
Phosphoric acid M. Ville prescribes in the form of super- 
phosphate ; whether he considers that it is equally beneficial 
if combined with bases other than lime, such as potash or 
magnesia, it does not appear. 
Potash he recommends in the forms of nitrate, sulphate, 
or potassium chloride, and here, as in the case of phosphoric 
acid, he insists on restoring to the soil, year by year, as much 
as has been removed by the crops. So far, therefore, he 
agrees substantially with the views of other chemists on the 
inorganic elements of plant-food. He differs from' them in 
the -importance which he ascribes to lime. In every one of 
his manurial formulae, no matter for what plant it is intended 
or to what kind of soil it is to be applied, gypsum — sulphate 
of lime — is present. The gypsum which he thus prescribes 
is, further, in addition to that formed in the manufacture 
of the superphosphate, and which amounts to no for every 
100 lbs. of pure tricalcic phosphate which has been used in 
the manufacture. It is also independent of the lime existing 
in the superphosphate in combination with phosphoric acid. 
M. Ville represents this unusual addition as having been 
proved itself in his experiments distinctly advantageous. 
But Messrs. Lawes and Gilbert in their experiments find 
gypsum a mere diluent. No one, of course, disputes that 
lime is for most plants an absolute essential, but in many 
soils it is present in quantities varying from 15 up to 90 per 
cent. Surely such a supply ought to be sufficient. If it be 
replied that the lime present in the soil exists in the state of 
carbonate, which is but very slightly soluble in pure water, 
it must not be forgotten that the water of rain and dew con- 
tains a supply of free carbonic acid, and is thus enabled to 
hold the carbonate of lime in solution. Besides many soils 
contain lime also in the state of sulphate. M. Ville, in 
maintaining that the other mineral constituents of the plants, 
including of course magnesia, maybe dispensed with in arti- 
ficial manures, asserts that even “ the worst soils are super- 
abundantly provided with them,” If this is the case, either 
