18 



THE GEOLOGIST. 



wall, had just realized. It amounted to the almost fabulous 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 mai'ket- garden land in the immediate neigh- 

 bourhood of London 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 the 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 quahties 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 afi'ord, 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, 



