30 Connection hetiveen Geolocjy and Agriculture in 



its agricultural qualities, tliough Me have here and there seen 

 some fair grass land, and better corn crops than might, at first 

 sight, be anticipated. As is \Yell known, the serpentine of the 

 Lizard offers a marked example of a particular plant, the Erica 

 vaga?is, a very beautiful heath, keeping to the soil upon it, so 

 that the boundary of the serpentine against the other rocks may 

 be fairly traced by its aid; indeed this plant is rarely found 

 beyond it. The general barren character of the serpentine of the 

 Lizard contrasts very forcibly with the soil on the adjoining dial- 

 lage rock and sienite, among the most fertile, if not the most 

 fertile, of the lands in the district. As Dr. Paris observes, " the 

 lands betw^een the church (of St. Keverne) and Coverack Cove 

 constitute one of the most extraordinary districts in the kingdom, 

 presenting a rare combination of rudeness and fertility; gigantic 

 boulders of sienite (and diallage rock) lying scattered in all di- 

 rections, and yet, in point of luxuriant fruitfulness, this country 

 may be denominated the garden of Cornwall.''* It affords, in- 

 deed, a good example of the unequal decomposition of a rock, so 

 that while it is sufficiently disintegrated in places, that pits may 

 be formed, and the decomposed rock taken away for manure, in 

 others hard blocks are scattered over the ground or rise in tors 

 through it : and it also exhibits an instance of the fertility of a soil 

 chiefly derived from the decomposition of hornblende, or diallage, 

 and felspar, the crystallization being large-grained. 



The hornblende slate and rock of the Lizard is also extremely 

 fertile, contrasting strikingly with the serpentine, which it bounds 

 in many places, and through which it, indeed, rises in small 

 patches in one or two localities, so that it is necessary not to con- 

 found the more abundant vegetation upon it with a growth upon 

 the serpentine. Some land near Lizard town, upon hornblende 

 slate, was, after being enclosed, not manured for several years, 

 though frequently cropped with barley and wheat ; so fertile is 

 the soil upon that rock. No doubt, from the mild temperature 

 of the Lizard district, where snow is rarely seen to rest upon the 

 ground, vegetation may possess advantages upon a given rock, 

 which it would not have in colder parts of Cornwall or Devon ; 

 but as at the same time it is much exposed to sea-winds, which 

 often sweep over it with great fury, and as the slates, greenstones, 

 hornblende rocks, diallage rock and sienite, serpentine, and talco- 

 micaceous rocks are all exposed to the same conditions, the 

 contrast afforded by the varied fertility upon these mineral com- 

 pounds is highly instructive, and illustrative of the fact, that soils 

 do, all other things being equal, mainly depend on their subjacent 

 rocks for their agricultural character. f 



* Trans. Geol. Soc. of Cornwall, vol. i., p. 189. 



t Speaking of the fertility of some lands in Mullion and other places near 



