472 



Sketches of the Meteorology, fyc. 



[Oct. 



nay, perhaps, for two or three thousand years, — thus proving the inac- 

 curacy of the opinion held by agriculturists, that if something be not 

 constantly added to land equal to what is taken from it, it must gradu- 

 ally deteriorate. Attention must be paid to the order of cropping, as 

 will he more particularly mentioned hereafter ; but, with this precau- 

 tion, the ryut is always sure of an abundant return, provided the wea- 

 ther he favourable.* 



It is probable that the fertility of this soil is principally owing 

 to its power of absorbing moisture from the atmosphere, which 

 is great, even when compared with the best soils of Britain. Sir 

 Humphry Davy says, " I have compared the absorbent powers of 

 many soils with respect to atmospheric moisture, and I have 

 always found it greatest in the most fertile soils ; so that it affords one 

 method of judging of the productiveness of land." He farther states, 

 that one thousand parts of a celebrated soil from Ormiston in East 

 Lothian, when dried to 212°, gained in an hour, by exposure to air 

 saturated with moisture at a temperature of 62°, 18 grains ; and that 

 one thousand parts of a very fertile soil from the banks of the river 

 Parret in Somersetshire, under the same circumstances, gained 16 

 grains. f The following are the results of some experiments I made 

 on the absorbent power of the cotton soil. I thoroughly dried a portion 

 of the soil, by exposing it for a long time to a heat that was nearly suf - 

 ficient to char paper. I then exposed 2615.6 grains of this to the 

 atmosphere of a moderately damp apartment, and found, after a few 

 days, that it had gained 147.1 grains. I now exposed it to an atmos- 

 phere saturated with moisture, and found that it daily increased in 

 weight till the end of a few weeks, when its weight was found to be 

 2828.4 grains. It had therefore gained 212.8 grains, or about 8 per 

 cent. 



In the hot season, the regur or cotton ground is traversed in all 

 directions by very deep fissures. In the rainy season it is in the form 

 of a very tenacious clay. Almost all the crops that are cultivated upon 

 it are sown towards the end of the rainy season, and therefore receive, 

 during their growth, comparatively little rain, and often, indeed, the 



In platma foil, it forms a lighter-coloured sla;*, having a greenish grey colour. 



" Fused into a solid mass in a large covered crucible placed in a furnace ; a crust of 

 oxide of iron gathered on its surface. 



" It consists of silica in a minute state of division, with portions of lime, alumina, and 

 oxide of iron. The proportion of vegetable and animal debris appeared to be very small. 

 Minute portions of the roots of vegetables were seen on close inspection with the naked 

 eye." 



* It will be an interesting subject of inquiry for future observers, to ascertain whether 

 any organic remains occur in this extensive deposite, to throw light on its origin, which 

 I think will not improbably be found to be diluvial. 



■t Elements of Agricultural Chemistry, p. ICO. 



