HARVARD

D

R DAY, in saying that I had come to take the place of the Secretary of Agriculture, reminds me of the remark of Oliver Wendell Holmes, on an occasion when by reason of the illness of Emerson he was sent to one of the lyceums to fill Emerson's appointment. The president of the lyceum stated that they had expected to listen to Mr Emerson, but by reason of illness they would not have that pleasure. However, Mr Holmes. had kindly consented to fill his place. Whereupon Mr Holmes on rising remarked that he hardly hoped to fill the place of Mr Emerson, but would attempt to rattle around in it a little; so to-day I cannot hope to fill the place of the Secretary of Agriculture, but will make as much noise in the large space unoccupied as possible.

ORIGIN OF THE SOIL

One of the oft-repeated theories concerning the origin of our earth is that at a remote period all the matter of which

JUN 29 1903

AMBRIDGE, MASS.

the earth consists at present was a part of the incandescent gas which filled the space now assigned to our solar system. As the cooling of this mass of gas progressed vortex rings were formed of gaseous matter. These on further cooling broke and rolled together, forming the sun, the planets, and the satellites of our present system. The next condition of the incandescent gas was incandescent liquid, which came in due season as the time rolled by. Finally, by the further process of cooling, a crust was formed upon the surface of these liquids which was the beginning of the solid surface of the earth. This crust would naturally be of the same composition as the liquid matter from which it was formed-practically homogeneous in character and consisting of the mineral matters which could only exist at that temperature.

In speaking of the soils of the United States, I would like to trace briefly their evolution from this primeval crust, which was the first ice formed on this

globe. What have been some of the more active forces which have broken up this congealed mineral matter and brought it into the present condition in which we see the surface of our globe? First of all I will speak of the action of water, which is and has been one of the chief disintegrating agents acting upon the earth's surface. At the time the first crust was formed over the surface of the earth all the water which now exists must evidently have been above the earth's surface in the form of steam. As the cooling progressed this steam tended to condense in the form of clouds and finally water. Thus the original rain falling upon the hot surface of the earth was at once converted again into steam, but not until it had started a certain solvent action. Water has been termed the universal solvent, and it is not difficult to see how active it must have been at the time of which I speak. The sudden cooling of the surface at the spot where a drop of water struck would tend to crack it, the hot water would dissolve quickly any of the substances soluble therein, and this continual bombardment of boiling water must have had a tremendous effect in disintegrating the original crust formed over the earth's surface. As the earth continued to cool and diminish in size, the original surface wrinkled and formed hills and valleys. The continual descent of water would finally permit some of it to remain in the liquid state upon the earth's surface, and this coursing down the valleys continued the disintegration, both by solution and attrition. The original mineral matters were thus brought into a form of solution or suspension, and, seeking their natural chemical affinities, began to form from the first igneous rocks the first sedimentary rocks. These are the rocks which we now see in strata, covering the greater part of the earth's surface. All these stratified rocks must have been laid down under the water, and thus we are convinced that the sur

face of the earth during the long period of the formation of the soil must have been alternately above and below the surface of the water collected upon the globe.

INFLUENCE OF ORGANIC LIFE

When organic life came upon the earth's surface a new disintegrating force was introduced. Organic life, even in its smallest forms, such as bacteria, acts with vigor in decomposing rocks. The larger forms, which produce rootlets, help this disintegrating process along. These roots find their way into crevices of the rocks, and tend to split them open and to admit water below their surface. Certain bacteria also tend to oxidize the nitrogen of the air and form nitric acid, known under the common name of aqua fortis, which has a vigorous solvent action on many kinds of rock.

DIFFERENT KINDS OF SOIL

In the process of further cooling, ice was formed, and this also tended to have a disintegrating influence. Water in passing into ice increases in volume, and this tends to break and disintegrate many bodies. Rock saturated with water thus tends to break up when the water becomes ice. During the period of the ice age when large glaciers moved over the earth's surface, the crushing and grinding effects of the ice had much to do with disintegrating the rock. The vast areas of glacial drift which form the soil of many of our Western States are evidences of the gigantic scale on which these ice mills of the gods slowly ground the stones of the earth into soil. When the soil is formed by the decay of rocks without the transporting action of water or ice being active, the soils are said to be formed in situ. When the products of soil disintegration are carried by water and deposited along the banks of the streams or at their mouths, the soil is called alluvial. When