Dr Davy*s Agricultural Discourse, 363 



is a substratum of carbonate of lime in the form of minute ovoid 

 granules ; of another in St Michael's, in which the same substance 

 is met with in the form of minute rhomboidal crystals uncohering, 

 after the manner of sand ; of a third in St Thomas', where adjoin- 

 ing a bod of calcareous marl is a deposit of siliceous earth in a very 

 finely divided state, essentially different from, but in appearance 

 perfectly resembling, chalk. These may be considered as curiosities; 

 but they are not unintelligent in their indications or uninstructive. 

 In connection with the general geological history they seem clearly 

 to prove, as I have already stated, that the soils of Barbadoes were 

 mainly deposited when the rocky substrata on which they rest were 

 lying at a considerable depth in the ocean, where they were formed ; 

 and that the great variety of soils which are met with, must have 

 been owing to the causes then in operation — rivers bringing down 

 the detritus of the mountains of the continent, currents in the sea 

 distributing them, and probably submarine volcanic eruptions, of 

 which there are indications here, disturbing them, and adding new 

 materials to complicate them the more. 



These may appeaar to some, theoretical views and visionary ; but 

 they assuredly are not so. The reading of geological signs is com- 

 monly unambiguous and easy. Like the reading of a written lan- 

 guage, it must be entered upon in its minute parts : these are, as it 

 were its alphabet. A sea-shell, the spine of an echinus, the tooth 

 of a shark, — the microscopic remains of infusoria, occuring mixed 

 with water- worn particles, — whether loose, as in beds of marl, or 

 compact, as in beds or strata of limestone, plainly declare their sub- 

 marine origin. And other sources are not less clearly denoted by 

 other appearances ; the form of the minute fragments constituting 

 volcanic dust and ashes is not to be mistaken, — each little fragment, 

 as seen under the microscope, presenting sharp edges and acute 

 angles ; and the form of river sand, especially of hard quartz sand, 

 altogether different from the preceding, all the edges and angles 

 worn by attrition, is equally distinct and significant. Such geologi- 

 cal interpretation is not merely amusing to the mind, but is valuable, 

 I believe, in connection with agriculture, viz., by aiding to give, as 

 it is well fitted to do, a true insight into the nature of soils. 



The qualities of your soils, to which we will now proceed and give 

 a brief consideration, as I have already observed, depend chiefly on 

 the elements composing them. Of these qualities, generally, two 

 views may be, and, I believe, ought to be taken ; one, as regards 

 their texture, which is commonly called their mechanical or physical 

 condition, as to the degree of sustaining firmness,^-of resistance to 

 the implements of husbandry, — of perviousness to air and water, and 

 of power of retaining water ; the other as regards their chemical 

 composition, considered as the source of the inorganic elements essen- 

 tial to the growth of plants, and which, when of the best quality, 

 should render the soils productive without aid from manures. 



