364 Dr Davy's Agricultural Discourse. 



Let us take now a hasty review of the principal varieties of soil 

 before named, in relation to these qualities. 



1st, Of the Calcareous or Chalk Soil. — This soil, besides being 

 composed principally of carbonate of lime, in a loose finely divided state 

 with some alumine, contains a certain portion of silica in the same 

 state, also of carbonate of magnesia and of phosphate of lime, and 

 doubtlessly of the vegetable alkali. From the nature of its consti- 

 tuent parts, and the state in which they are, this soil, physically con- 

 sidered, may be held to be almost the perfection of a soil ; cool from 

 its colour reflecting the sun's rays, — absorbent of moisture, and not 

 too retentive of it, allowing the rain to descend deeply into it, and to 

 be kept in store amongst its pores, — to ascend and be exhaled as 

 moisture on the occasion of drought ; sufficiently firm to give due 

 support to plants, and sufficiently yielding to be easily worked. 

 These, it must be admitted, are excellent qualities. And as regards 

 its nourishing power, through the medium of the inorganic elements 

 which it is capable of supplying, its character is of a very high kind, 

 as the elements which it contains are those which appear to be most 

 essential to the staple and more important crops of the island, — such 

 as the sugar cane, Indian corn, yam, and others. This soil, with, 

 these excellencies, may, I believe, be held up as an exemplar. Its 

 productive powers appear to be high. Without manure, I am 

 informed, it wilL yield good crops, even of the sugar cane ; and 

 this successively for several years, without fresh planting ; and it is 

 worthy of remark, that the sugar, the produce of these canes, is 

 esteemed above the average quality, and is obtained in proportionally 

 large quantity. The estimation in which soils of this kind are held, 

 is pretty well indicated by the rent which can be obtained for them, 

 viz., from twenty-four to thirty dollars an acre, and even, I believe, 

 occasionally, as high as thirty-five ; and this in situations commonly 

 of difficult access, remote from the town, and having little but the 

 fertility of the soil to recommend them ; such as the steep declivi- 

 ties of Mount Hillaby, the highest part of the island, the chalk soil 

 of which, rising at least 1100 feet above the sea, is cultivated to the 

 summit ; the rugged ground in the neighbourhood of Castle Grant ; 

 and that little district of similar ground, which has received the name 

 of Irish Town. 



The other calcareous soils of the island, in widely different situa- 

 tions, are more or less analogous to the chalk soils, such as the marl 

 soils already noticed, and the calcareous argillaceous soil of the Cod- 

 rington College Estate ; they have a great resemblance in their ele- 

 mentary composition, varying chiefly in the proportions of their con- 

 stituent parts ; and they are, 1 understand, all remarkably fertile. 



2dli/, Of the Clay Soils. — The qualities of these soils, as of clay 

 soils generally, are strongly marked. It may suffice to describe 

 them very briefly. They are retentive of moisture in a very remark- 

 able manner, and, at the same time, little pervious to air and mois- 



