THE MAGAZINE 
OF 
THE SCHOOL OF AGRICULTURE, 
COLO WL BO. 
tfffiti /Iffik <^E>_^^^_j|^h_ilttfc_jfl) 
Added as a Supplement monthly to the "TROPICAL AGRICULTURIST." 
The following pages include the contents of the Magazine of the School of 
Agriculture for October : — 
HOW DOES SCIENCE HELP AGRICULTURE? 
■ IV. 
By C. Driebebg, b.a., f.ii.a.s. 
Geology as an aid to agriculture treats of rook 
formation and the history of soils. All soils have been 
formed out of rock, by the process of weathering, 
which may be described as the work of the agents 
which assist in breaking up rocks and making them 
suitable for plant food and for fixing the plant, The 
weathering agents may be classified as follows :— 
I. Mechanical agents such as (1) glaciers, (2) stones 
and sand rolling down river beds and helping the 
water to produce greater erosion, (3) waves and tides, 
(4) sand blowing against the face of a rock, (5) wind, 
(0) rain drops, 
II. Chemical agents as (1) oxygen, (2) water as a 
solvent, (3) carbonic acid in water, (4) the juices of 
plant roots. 
III. Thermometric agents as (1) frost, a most 
powerful disintegrating agent, (2) heat. 
IV. Animal agents as earthworms, &c. 
The interesting manner in which each of these 
agents works — some, such as, earthworms doing an 
amount of work, which few credit them wilh— cannot 
be gone fully into in this series of articles, for it is 
not intended at present to bring together all the 
interesting facts which the sciences contribute to agri- 
culture, but merely to indicate how they do help, and 
in what branches of agriculture they step in as 
auxiliaries. 
When it is said that soils are derived from rock' 
it is not to be supposed that where a certain rock 
formation prevails, there a particular soil must charac- 
terize the locality, though this is exceptionally the 
case. In the latter instance, when the soil or weathered 
rock is found to overlie the living rock from which it 
was derived, we have sedentary soils ; while in the 
former, that is where the soil has no great resemblance 
to the underlying rock, and does not suggest that it was 
derived from it, we have transported soils. Transported 
soils_ are such as have been brought from a distance 
by various agencies, such as : — (1) glaciers, (2) the 
sea, (3) rivers, (4) wind, (5) volcanoes. 
The organic portion of rock in soil may have been 
derived in many ways. In the organically formed 
rocks — limeston for instance — we can understand how 
the remains of the organisms which help to build up 
the formation contributed a supply of organic matter. 
In a similar manner the remains of fossilized plants 
and animals add organic matter to rocks to some 
extent. In soils the growth and decay of generations 
of lower vegetable organisms have furnished the 
necessary supply for plants of a larger growth. Be- 
ginning' with the lowest forms of vegetable life these 
accumulations have gone on till natural forests have 
been enabled to thrive luxuriantly. 
Knowing therefore the composition of rocks, or 
rather the composition of minerals forming the rock, 
we get a fair idea of the composition of soils. 
Knowing also the history of a soil (as we should from 
a knowledge of geology), that is the manner in which 
it was formed and left where we find it, we get a 
still better idea of its nature and character. And 
thus we get information of economic value, for we 
will thus be able to decide what crops should be 
cultivated on certain soils, knowing what conditions 
both as regards mechanical texture and chemical 
composition favour particular families of plants. 
Again we would have a general idea as to what 
manures, if any, we should add. Where, moreover, 
we have facilities for studying the stratification of 
a country by means of the informatfon supplied by 
