238 Analyses of Books. [April, 
beds and sea, is in many districts accelerated by the “ adtion of 
burrowinganimals.” We have often noticed that in slopes infested 
by rabbits, their holes seem to give the rain a special point of 
attack. 
The following remark is true and sad: — “To the traveller 
through the Southern States, the pictures presented so often 
around the older villages and towns, of red clay hills, gashed and 
scored by unsightly gullies, are all too familiar.” 
The very same process has been carried on for a much longer 
time in all the countries of the Mediterranean Basin. It has 
been taken up in Central Europe, and in all European Colonies 
— British, French, Spanish, or Dutch. In short, desolation fol- 
lows wherever the forests have been generally removed, whether 
by war, by the adtion of goats and camels, by fires, or by human 
greed. An American observer has wisely remarked, not long 
ago, that if one-fourth of a country is allowed to remain covered 
with trees and bushes, the remaining three-fourths will yield more 
food for man than would the whole if denuded. 
As regards the exhaustion of soils, the author quotes from 
Mayer a very instructive remark explanatory of the fadt that 
phosphoric acid must be present in the soil in much larger quan- 
tities than is adtually needed for the present crop. The phosphates 
in the soil are insoluble, and must have come into diredt contadt ) 
with the capillary fibres of the roots before they can be assimi- 
lated. But as only a limited number of such particles can come 
into adtual contadt with the roots, only a small proportion of the 
phosphate present can be assimilated during one season. 
Dr. Smith gives particular prominence to potash, nitrogen, and 
phosphoric acid as the three elements of plant-food most likely 
to be exhausted. As regards lime, to which M. Ville assigns an 
almost equal rank, our author holds that when added it serves not 
so much as plant-food as to produce changes in the other ingre- 
dients of the soil which render them more easy of assimilation. 
The author’s explanation of the manurial effedts of gypsum is 
that it replaces the bases, especially potash, absorbed by the 
plants. He notices also the surmise of Heiden, that by a con- 
centration of the soil-fluids it diminishes the transpiration of 
moisture through the leaves of plants, so that a dressing with 
gypsum may enable a crop better to resist the adtion of drought. 
He admits, however, that no theory as yet put forward fully ex- 
plains the beneficial adtion of gypsum on leguminous plants and 
its uselessness for cereals. 
We regret that we cannot further pursue our examination of 
this work, which must be recognised as possessing no mere 
ordinary degree of merit. 
