296 Arboriculture in relation to Geology. 



good return may also be obtained by cultivating the SsMyl 

 rubra for basket twigs, in the interstices of the other trees, 

 until their growth smothers the willow stools. 



As we advance from the chalk hills to the north-westward, 

 the calcareous stratum of extent and importance which we 

 next meet with is the great oolite, or Bath freestone rock. 

 The trees upon this stratum do not materially differ from 

 those which invest the chalk. If it usually is covered with a 

 bed of hazel calcareous loam, of greater depth than commonly 

 lies over the chalk, yet the rock, v^hen we come to it, is 

 generally more compact, harder, and more difficult to be 

 trenched, than the chalk. The elm flourishes on this stratum 

 more freely than on the chalk. I have had no opportunity of 

 observing any experiment on the culture of the alder and 

 poplar tribe on this stratum ; but, the substance of the stone 

 being less porous than the substance of the chalk, I should 

 be thereby led to expect that these trees would not succeed 

 equally well here as on the chalk. I have seen the abele 

 growing spontaneously and vigorously on this stratum. In 

 the valleys which cut this stratum is usually found an extra- 

 ordinary depth of rich friable loam, in which the SkYiyi fragilis, 

 or crack willow, and some others of the large willows, attain 

 a great stature. The next great calcareous stratum, as we 

 pass to the north-westward, is the mountain limestone, car- 

 boniferous or metalliferous limestone. This stratum is, in 

 some respects, modified from the two preceding, by portions 

 of a purple ferruginous clay, which, in certain places, are 

 interposed in joints or other cavities of this rock, and also 

 by layers of chert, and others of firestone, i. e. impure 

 siliceous limestone, alternating with the beds of mountain 

 limestone ; and these heterogeneous rocks, and their detritus, 

 in some parts materially affect and modify the soil which is 

 spread over this stratum. We find on the mountain lime- 

 stone (many of the vegetable products of which have been 

 well elucidated by a correspondent in the Magazine of Natural 

 History, vol.iii. p. 410 — 419.), the sycamore {A^cex Pseudo- 

 Platanus), the Py rus hybrida, and most of the preceding plants 

 which I have mentioned as natives of the chalk. The holly 

 (/4ex ^quifolium), too, is found here more frequently than on 

 either of the preceding calcareous strata ; fostered, no doubt, 

 by the more abundant silex, which is supplied by the detritus 

 of the interposed beds above mentioned ; and, from the same 

 cause, the [T-lex europae'a (whins, or French furze) usually in- 

 vests in considerable plenty some of the uncultivated portions 

 of this stratum. 1 remain. Sir, yours, &c. 



Sept. 20. 1832. Causidicus. 



(Zb be continued.^ 



