422 Scientific Proceedings, Royal Dublin Society. 
enable one to forecast the degrees of natural fertility which should 
be expected in different localities. ‘To a certain extent this hypo- 
thesis holds, but, in our latitudes at least, it is subject to consider- 
able modification, which it is one purpose of this paper to define. 
Few in this day will dispute that soils are derived from the 
solid rocks which form the crust. When, however, one examines 
the detritus (mingled clay, sand, stony particles, etc.) resulting 
from rock decay throughout the country, and finds materials 
obviously derived from limestone strata, overlying granite, as 
in parts of the county of Dublin, and covering Silurian grits, 
as in parts of Wicklow and Wexford; débris of metamorphic 
rocks over limestone in Sligo, and over granite in Donegal, 
etc., it is not unnatural that some would question whether 
the disposition of geological strata has any direct bearing 
upon the local character of their earthy covering. Nor are such 
questions confined to the uninstructed. The lucid and well- 
informed author of a work on the “ Principles of Land Valua- 
tion,’ signing himself “Aleph,” apropos of this, says: ‘“ The 
relation between the soils and the underlying rocks is such, that 
any classification of the rocks, as, for instance, the division of 
the limestone into four descriptions, can be of no agricultural 
importance whatever.” The circumstances alluded to are, I 
believe, to be accounted for by transplacement of rock detritus, 
which have obtained on a grand scale through the agency of 
land ice, and possibly of icebergs ; and such departure from what 
may be regarded as the natural order of things, has been attended 
with marked advantages to the agricultural interest, such as— 
(1). A greater extension than would otherwise obtain of 
fertilizing materials. 
(2). A mixing of materials drawn from different sources, 
which generally conduces to fertility. 
The transplacements mentioned above have resulted in the 
present distribution of soils and subsoils, which we may speak of 
combinedly as Drift; and in this aggregate view of it we may 
conceive of an extensive covering made up of a confused mixture 
of stones and earth, robing two-thirds of the country or more; 
1 E. Ponsonby, Dublin, p. 68. 
