22 Connectlun between, Geoloijy <ind yl<jrlcidture in 



is an evident connection between the greater or less productive- 

 ness he may have noticed, and the areas differently tinted in the 

 map. Those who examine more minutely into the subject will 

 soon perceive that this coincidence extends very generally to the 

 boundary-lines of the various colours ; so that, if the scale of the 

 map be sufficiently large, the relative fertility may, in some cases, 

 be traced even across fields, portions of them being far more pro- 

 ductive than others. 



In endeavouring to estimate the relative amount of fertility 

 that may be due to the decomposition of the subsoil rocks, it is 

 essential that due attention be paid to local conditions as regards 

 aspect^ height above the sea^ and other necessary circumstances, 

 otherwise many erroneous conclusions may be drawn, especially 

 in a country like that we are now noticing, in which so many 

 places are exposed to the influence of the sea-winds, and where 

 heights vary considerably. We should necessarily expect that 

 sheltered situations, with a good southern aspect, wonld be those 

 in which, all other things being equal, Ave should find the capa- 

 bility of any given soil best exhibited ; and that hence, by com- 

 paring localities as nearly alike in this respect as we can find 

 them, we may be the better able to observe any differences which 

 may arise in soils from the mineral structure of the subjacent 

 rocks. 



Fortunately there are many short valleys on the southern 

 coasts of Devon and Cornwall, the component parts of which do 

 not so materially vary in latitude as to render their temperature 

 on that account, , to any very important extent, different, where 

 the general atmospheric conditions are so nearly similar, that the 

 relative fertility of the soils in them may be fairly appreciated, 

 due allowance being made for the greater prevalence of cloud as 

 we proceed westward, viewing the district as a whole. At Lyme 

 Regis we have a lias valley, and at Sidmouth one formed of red 

 marl and sandstone, both bounded by hills of green-sand, and 

 both much strewed over in places by flint and chert-gravel. The 

 superior fertility of the Sidmouth valley is readily seen, though of 

 the two it is most exposed to the northerly winds. Independently 

 of the decomposed lias being less favourable to general cultiva- 

 tion, though it is commonly valuable for grass-land, the geological 

 conditions of the two valleys are such that, while the rain-water^ 

 which percolates through the green-sand on the tops of the bound- 

 ing hills, is allowed to pass through the red sandstones in the 

 valley of Sidmouth, being thrown out only by the marls, the lias 

 in the valley of Lyme throws it out altogether, producing land- 

 slips and much wet ground. 



If we compare the short valleys, with a southern exposure, of 

 Lamorna Cove (on the west of Penzance), in granite, of Chyan- 



