Lees : On the Proposed New Map of Yorkshire. 53 



Secondly, the soils, for which plants have preferences, depend not 

 so much upon the very varied chemical differences in the strata under- 

 lying them as upon the broad and well-marked lithological peculiarities 

 of the different groups of rock. These peculiarities, chiefly in their 

 varying behaviour under the disintegrating action of water, influence 

 the soil. There are two great (and one intermediate) types of rock 

 in respect of mechanical constitution, corresponding with which 

 all the soils in the county are divisible into three correlative groups. 

 One type of rock is hard, yields detritus sparingly, yet as a mass is 

 cracked and fissured so that water runs off it easily. Such are the 

 oolitic, permian, and scar-limestone strata. The other great type is 

 hard as to its siliceous particles, but these are bound together in a 

 more pliable matrix, it is easier abraded by weather, in beds it holds 

 water above it, and often where shaly and clayey bands are interposed 

 in it too. Such are the slates, gritstones, and coal shales. 



The soils covering the dysgeogenous (first-named type) rocks are 

 often scanty, but always dry, warm, fertile, and richer in their 

 admixture with vegetable humus The soils overlying the grits are 

 heavier, wetter, less fertile ; those overlying the clays and coal shales 

 typically cold, stiff, and wet. 



There is a third type of rock, represented by the red sandstones, 

 liassic, and Yoredale limestone shales, which are lithologically of 

 intermediate character. So are their soils intermediate, sandy, and 

 rather dry, and fairly fertile, or dampish but calcareous and rich. 



These three kinds of rock have, then, not only a great effect upon 

 the configuration of the hills and valleys — the scenery, but greatly 

 influence the vegetation above them ; and these, I would suggest, are 

 all the soil differences it is really necessary to express upon our map. 

 They show a broad geology, and point the main ascertainable features 

 of phyto-geography. For no plants (so far as is known) is one 

 particular kind of limestone earth a necessity ; so that the advantage 

 on our map of showing upon it the strike-lines of the upper and lower 

 oolites, of the various grits, and of the upper and lower permian 

 strata, would be nil so far as the distribution of plants and animals is 

 concerned. Where we do find a few species restricted to one 

 particular stratum, say the scar-limestone, it is not that they prefer 

 that rock to any other, but it is due to that accident of altitude that 

 within our area the upheaval of scar-limestone alone gives. 



III. Eemarks on River-Basust Division. — A division into river- 

 basins has only one very small advantage over the most arbitrary and 



tificial parcelling out of an area into squares, or whatever else is 



