Annlijscs of the, Ashr.-^ of Plants. 
Ill 
The total sulphur removed in a ton of hay, and the quantity of 
sulphuric acid to which it is equal, are as follows : — 
Reii Clovei' . . 7-3 lbs. == 18-2 lbs.* sulpliuiic acid. 
White Clover . 9-3 lbs. = 23-2 „ „ 
It will be asked, do the foregoing analyses throw any light upon 
the cultivation or peculiarities of clover? 
Of course any observations that can be made here have 
reference only to the mineral matters of the plant, and are there- 
fore in no way to be considered as comprehendmg the whole 
question. Taken solely in reference to its mineral composition, we 
should be induced to call clover an exhausting crop — that is, when 
the produce is removed in the state of hay. A fair crop of red or 
while clover would, indeed, with the exception of silica, carry off 
fully^'as much of the mineral wealth of the soil as an average crop 
of wheat or barley ; but there is, it is conceived, nothing in the 
analyses of the clover here given that would justify us in attribut- 
ing the difficulty of its cultivation to any peculiarity in mineral 
constitution. It was hoped that the analyses might throw some 
light upon the use of gypsum to the clovers, although, amongst 
practical men, it is still a subject upon which very conflicting 
opinions are entertained. Granting, for the sake of argument, 
that gypsum is beneficial to clover, is its action referrible, as 
Boussingault maintains, to the lime of the compound ? Does it 
benefit the plant by the sulphuric acid or sulphur it supplies? 
or lastly, are we to believe, with Liebig, that it is simply as a 
vehicle for the collection and presentation to the plant of ammonia 
that we are to regard this substance when employed as a top- 
dressing to clover ? 
The only one of these theories which the results we have 
presented will allow us to speculate upon is that of the supply 
through gypsum of sulphur and sulphuric acid. 
At first sight we might be disposed to attribute some con- 
siderable share of this effect to the cause mentioned. A ton of 
white clover-hay contains, in one form or another, 9-3 lbs. of 
sulphur, which, in the absence of any proof that compounds of 
sulphur are derived by vegetation from the air, we must believe 
to have been supplied by the soil. ^ 
9-3 lbs. of sulphur are contained in about 23*2 lbs. of sul- 
phuric acid, which quantity would be furnished by 50 lbs. of pure 
gypsum, or, in round numbers, by \ cwt. of the common com- 
mercial article. This is certainly a large quantity ; and it might 
be doubted whether, in all cases, the natural supply of sulphuric 
acid in the soil would be adequate to meet the demand ; but we 
shall have occasion to show that many crops, to which no one 
w-ould think of applying gypsum, do in reality carry off far more 
* Dry sulphuric acid (S O^). 
