18 
THE GEOLOGIST. 
wall, had just realized. It amounted to the almost ftibulous sum of 
twenty pounds an acre, with a covenant, on the part of the lessor, that 
he should still reserve to himself the right of drawing one crop per 
annum. The richest market-garden land in the immediate neigh- 
bourhood of Loudon does not fetch (so far as I am aware) more than 
twelve pounds an acre. I was informed, too, this was no unusual 
price for many plots on the Cornish coast, and, though the price may 
not range so high as this in any of the Scilly Isles, there can be no 
doubt that the soil is equally fertile, and the advantages of climate 
perhaps even superior to those of the most favoured Cornish fields. 
It may seem strange that a group of granite rocks should supply the 
London markets with vegetables of a superior quality to those pro- 
curable from places apparently much more eligibly situate ; but, 
nevertheless, it is a curious fact, that large fortunes have been, and 
still are being made, by sending up to tlie metropolis innumerable 
baskets of early potatoes — the growth of which is fostered not more by 
the genial character of the winter in these lonely isles than by the 
valuable qualities and admixtures of soil which have resulted in the 
course of ages from the decomposition and disintegration of the 
granite. I think it probable, also, that from the very circumstance 
of much of the soil lying immediately above the granite, it would 
enjoy a double advantage, viz., that of the radiation of heat upwards 
from the solid rock, which would obviously retain any imparted 
warmth derived from the sun's rays for a longer time than a less 
compact subsoil ; secondly, the retention of a certain amount of 
moisture from the inability of the rain to sink very low beneath the 
surface. Certain it is, that with very slender means of manuring, 
except with burnt sea-weeds and crushed shells from the sea-shore, 
very abundant crops of cereals are continually reared, not only in 
St. Mary's, but in all the other inhabited islands, while even those 
which are now uninhabited afford, by their decaying stone-hedges and 
walls, proofs that most of them have been once fully cultivated, and 
are still capable of supporting a large number of inhabitants. « 
The various soils which are to be found superimposed upon the 
granite in the Island of St. Mary — and, so far as I could observe, the 
order and relation of them seemed precisely the same in St. Martin's, 
St. Agnes', and Tresco — were the following : 1st. A black surface-soil. 
