Dormant and Active Ingredients of the Soil- 
237 
capable of juds^ing what would be improvements; because he 
would only have to pay for part of what he had got ; and, in 
such case, if there were no improvements, there could be none 
to pay for. 
23, Alexander Square, Brampton, 
near London. 
XVI. — On the Distinction between the Dormant and Active Ingre- 
dients of the Soil. By Dr. Daubknv. 
In the Bakerian Lecture for 1845,* I took occasion, whilst 
treating of the Rotation of Crops, to insist upon the distinction 
between what may be termed the dormant and the active ingre- 
dients of a soil with reference to the plants that grow in it. 
When we consider, I remarked, the nature of a soil in an agri- 
cultural point of view, or in reference to its suitableness for the 
growth of various kinds of vegetables, two questions naturally 
come before us ; namely, what amount of ingredients capable of 
being assimilated in the course of time by the crops does it con- 
tain ; and secondly, what is the amount of those which are present 
in a condition to be actually available for their purposes, at the 
precise moment when the examination is undertaken. 
Both the above points are obviously quite distinct from that 
relating to the total amount of ingredients which exist in it, and 
hence some might be disposed to add to the labour of the two 
preceding investigations, that of ascertaining the whole of its con- 
stituents, whether in a state to be affected by the ordinary agents 
of decomposition, or not. 
The latter question, however, seems to me to possess, with re- 
ference to the agriculturist, only a speculative interest, and when 
introduced into a report intended for his use, may be more liable 
to mislead than to instruct, unless due caution be taken to point 
out to him, how much of each ingredient is to be regarded 
as inert, and how much of it as applicable to the future or present 
uses of the plant. 
Let us take the case of a natural soil, composed of certain kinds 
of disintegrated lava, or even of granite, in which it is evident, 
that an actual analysis, conducted by means of fusion with barytes, 
or lead, or by any of those other processes which chemists employ 
for decomposing compounds of a refractory nature, would detect 
the presence of a large per centage of alkali, not improbably of a 
certain amount of phosphate of lime, and in short of all those 
ingredients which plants require for their support in sufficient 
abundance. Nevertheless, land of this description, in conse- 
* Philosophical Transactions, Part ii., for 1845. 
