Dormant and Active Ingredients of the Soil. 
•239 
any kind of plant after fallowing, must be assumed to possess in 
itself an adequate supply of all the ingredients necessary for its 
support in an available condition ; but it is plain that these could 
not have existed in an active one, or such an interval of rest would 
not have been required for rendering them efficient. 
Accordingly it is quite possible, that after ten years' cropping, 
the soil of my experimental garden might still retain plenty of 
alkaline salts and phosphates, although what was ready to be 
applied to the uses of the plant had for the most part been ab- 
sorbed by the crops previously obtained. 
With a view then to this branch of the inquiry, I first ascer- 
tained the nature and amount of the ingredients separable from a 
given weight of the soil by means of muriatic acid, and 2ndly, 
those obtained from the same by a definite quantity of water im- 
pregnated with carbonic acid gas. By a careful analysis it was 
ascertained that the soil of the Botanic Garden at Oxford con- 
tained, within an area of 100 square feet, and a depth of 3 feet 
from the surface, 3 5 lb. of phosphoric acid, 6*9 lb. of potass, 
and 2 • 9 lb. of soda, all in a state to be separated from the general 
mass by muriatic acid. 
That the above, however, were for the most part in a dormant 
condition, appeared from the much smaller amount of the same 
which could be extracted by water containing carbonic acid, for 
it was found that of alkaline sulphates* not 1 1 lb. could be pro- 
cured by these means, whereas 
6' 9 lb. of potass would have formed 12' 7 
2- 9 lb. of soda . . .6-5 
Together . 19-2 lb. 
Extracted by carbonic acid water . 1 1 • 0 „ 
Difference . 8'2 „ 
and that of phosphate of lime only 7134 gr., or less than 14 
ounces were obtainable ; whereas 3*5 lb. of phosphoric acid, 
equal to near 7"0 lb. of phosphate of lime, had been taken up by 
muriatic acid from the same. 
By operating in a similar manner upon soils of the same qua- 
lity as the above, which had been exhausted by several years' 
previous cropping, it appeared, that whilst the amount of the 
ingredients alluded to as dormant in the soil did not much vary in 
the two cases, that of the active ones was beyond all comparison 
greater in the sample of unexhausted soil. 
This will appear from the following table : — 
* The alkalies were estimated as sulphates, as it was found convenient 
to unite them with sulphuric acid, in which state they admitted of being 
heated and weighed without incurring loss. 
