DISTRIBUTION OF SOILS. 
211 
<ihat this variation is confined between the limits of a southeast and a southwest course, 
with a few interesting exceptions which will be given in the sequel. The number of re¬ 
corded observations which go to establish the general fact of a southerly distribution of the 
soil and boulders, is extremely great, and is gathered from the whole extent of country 
between the Atlantic ocean and the base of the Rocky mountains ; and no instance has 
happened in which a boulder has travelled northwardly, or been found in a situation with 
its parent rock towards the south. The two great facts, then, which geologists have been 
able to establish on this question as general, are, first, the transportation of rocks and soils ; 
and, secondly, the southerly direction in which they have been uniformly carried. Ac¬ 
cording to this general announcement, a soil occupying any given situation, if out of place, 
lies south of the rock which gave it origin; and the pebbles which are large enough to be 
readily distinguished, indicate the origin of the soil, or the rock to which it belongs. If 
we find many limestone pebbles, or if lumps of earth are found to effervesce with vinegar 
or other acids, it shows that the soil is formed of the debris of a calcareous rock. 
A soil which contains many pebbles, or rolled stones like paving stones, is frequently 
called drift , a term which is convenient, as well as short. All soils which have been 
transported, may be termed drift; but where cobblestones make up a large proportion of 
a formation, the evidence of its having been drifted is obvious, and hence the term is 
usually confined to beds exhibiting these sure marks of transportation. The term drift , 
however, would not be properly applied to a pebbly beach. 
Scored surfaces. The second phenomenon above mentioned, which is believed to he 
somehow connected with the transportation of soils, is an effect observed upon hard sur¬ 
faces over which the drifting soil has passed. The upper surface of most hard rocks, of 
whatever age they may be, is scratched, grooved, or sometimes polished. These effects 
differ at different places, according to the nature of the materials which have passed over 
the surface. If these materials were coarse and heavy, deep scorings seem to have been 
the only result; if of a finer texture, the surface is slightly scratched, or it may be polished, 
an effect which can not be produced by coarse substances. The markings vary in degree, 
from the slightest scratch, to-a groove four or five inches in depth. The direction of these 
scratches or grooves is southerly; and it is a curious fact that they are not made in vary¬ 
ing directions, and without order, but always correspond to the direction which, from other 
considerations, we find the soil to have taken in its transportation: in other words, the 
grooves run in a southerly direction, and are parallel in sets; and, as a general rule, their 
directions are confined within the limits of the southeast and southwest points of the com¬ 
pass. From this correspondence between the direction of the grooves, and that of the 
transportation of the boulders and soil, we are legitimately authorised to associate the two 
phenomena as cotemporaneous effects of one common cause, whatever that cause may 
have been. This interpretation seems to be borne out by the fact, that in uncovering a 
rock of its soil, which we usually denominate drift , the bottom boulders are frequently 
found each occupying the groove it had made, like a plough left in its furrow; and like 
27' 
