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those which refer to the other modifications of universal force — heat and 
light. It is shown that, by the mutual co-operation of these various 
influences on the one hand, and the organized germ of the plant on the 
other, the latter eventually assumes its definitive form. Numerous experi- 
ments are cited to prove the doctrines laid down ; and the author then 
proceeds to the subject of radication , or the nature and form of roots, which 
has hitherto been too much neglected, especially by our English agricultural 
chemists, who have fallen into serious errors that a thorough knowledge of 
botany would have enabled them to avoid. Stress is laid upon the fact that 
one class of plants obtains its food from the subsoil, while another derives 
it from the arable surface ; the former being represented by the turnip, and 
the latter by the cereals. In Chapter II. we are treated to a history 
of soils, of their varied compositions, and their relations to the roots of 
plants. Here the author dwells upon the circumstance that soils possess 
the power of abstracting the mineral food of plants from its solution in 
either pure or carbonic acid water, and of then retaining it. It is showm, 
too, that a crop may fail from the absence in the soil of some one parti- 
cular form of food, although the other necessary constituents may be 
present ; and the reason why wheat may flourish on the same ground 
which refuses to grow rye, is given in the clearest manner. The third 
chapter embraces the description of the various classes of manure, their 
chemical and agricultural qualities, and the reasons why it is necessary to 
have a uniform distribution of the food-elements of manures. The more 
important feature of this portion of the text — indeed, we may almost say of 
the entire volume — is that, here, the errors of Messrs. Lawes and Gilbert are 
unsparingly exposed. Clover- sickness, as it is termed by farmers — to 
whom, by the way, its cause has always been an enigma — was taken in 
hand some years since by the two English chemists referred to. They 
made it their especial hobby, and trotted it out on every possible occasion, 
as one of their triumphs in the chemico-agricultural direction. It turns 
out, however, that their hypothesis is a sham, a wild speculation, unsup- 
ported by the results of experience, and, as Baron Liebig convincingly 
demonstrates, overthrown by the very experiments of its originators. 
Clover, the author shows, is one of those plants whose roots descend to 
considerably greater depths than others, and, in reality, obtains most of 
its nourishment from the subsoil. But this is not all. Owing to the small 
quantity of nutritious material which the seed contains, it is obliged, even 
in the early stages of its growth, to abstract food from the soil, and there- 
fore it robs the arable surface as well as the deeper strata ; and when its 
roots reach the subsoil, those of them which still lie in the upper layer 
become so suberous in character as to lose the power of removing mineral 
elements from the earth ; hence in its later days it feeds upon the subsoil 
exclusively. It sometimes happens that a crop of clover which during 
winter looked remarkably well, becomes sickly as spring advances, and, in 
course of time, perishes entirely. This is what is designated clover sick- 
ness, and what Messrs. Lawes and Gilbert took upon themselves to explain ; 
and this is their explanation : — Clover feeds upon organic matter of a 
complex kind, whilst cereals live upon minerals chiefty. Now, it is a most 
remarkable circumstance that these experimentalists, in operating upon two 
