462 Retrospective Criticism* 



vegetables, and that secondary and diluvial districts are distinguished by 

 poverty and slow production. I leave, for the present, the discussion of 

 the question, whether primitive or secondary formations produce the 

 greater variety of plants, because this is by no means identical with the ques- 

 tion whether they produce the richest specimens. I do not know whether, 

 when Mr. Thomson speaks of " diluvial,'* he means to include alluvial 

 strata; but I conclude that he does, otherwise he would be omitting un- 

 noticed extensive tracts of country which cannot be included among 

 primitive ranges, and therefore, unless they are classed with the secondary 

 and diluvial, must go altogether unnoticed. Understanding him thus, I 

 venture to deny his assertion. The soils which invest the primitive rocks 

 in this kingdom are far less fertile than those which clothe the rocks of 

 secondary formation ; but the richest of all the soils are on the alluvial and 

 diluvial deposits. It happens, indeed, that the country about Liverpool, 

 and the adjoining parts of Lancashire, consist of an alluvial detritus of the 

 coal measures and adjacent sandstone, which is extremely poor and barren; 

 but the vales of Evesham and Taunton Dean, the rich meadows which 

 follow the course of the Bristol Avon, the fertile marshes of Romney, 

 of Lincolnshire, of Somersetshire, of Pevensey, of Gloucestershire on the 

 Severn, the rich pastures of Crediton, v/hich is the most productive land 

 in Devonshire, and very numerous other spots of superior soil to which 

 I might refer, are all either situate on the secondary strata, or composed 

 of the detritus of it ; while very few indeed are the spots where the detritus 

 of the primitive rocks forms so good a soil. 



I am not sure whether I misapprehend Mr. Thomson in supposing that 

 he attributes the presence of samphire, cabbage, and Plantago raaritima, on 

 Orme's Head, simply to their affinity for the mountain limestone ; but, if he 

 does, I am induced to think that he has not marked them with sufficient 

 discrimination. Besides the presence of mountain limestone, the presence 

 of sea salt, or one or more of its ingredients, is necessary to make these 

 plants flourish. He would in vain seek for them on the inland ledges of 

 Chedder Cliff; and he justly observes, he could not find the samphire on 

 St. Vincent's Rocks. Although the tide below these rocks is saline, the 

 river is so land-locked, that no spray can dash against the heights ; and the 

 maritime plants are mostly confined to the ooze at the water's edge, and 

 the lowest portion of the rocks. 



Mr. Thomson says " G'eranium pratense is, I am persuaded, to be found 

 luxuriant only in basaltic districts." Now, throughout the south of Britain, 

 in almost every sound, deep, rich, loamy soil, in which the various com- 

 ponent earths are moderately balanced, not excluding a good proportion of 

 calcareous earth, argil, and silex, this beautiful plant thrives luxuriantly. 

 On the fertile green sand of the Vale of Pewsey in Wiltshire, on the 

 sound calcareous loam over the great oolite, on the new red sandstone beds 

 of Somersetshire, and on the rich alluvial beds that accompany the course 

 of the Bristol Avon through Wiltshire, Somerset, and Gloucester, and on 

 the old red sandstone of Gloucestershire, this G^eranium is both abimdant 

 and magnificent. 



Foxglove, which Mr. Thomson says is common every where but on 

 chalk, is not, in truth, common, unless on soils where there is abundance 

 of silex; but on all calcareous strata, and on clays, the foxglove is not 

 spontaneous, and can scarcely be made to grow ; and although it is now 

 many years since I visited the Isle of Wight, I should be extremely sur- 

 prised were I to find in the stratum of grey sand, which crops out below 

 the chalk and forms the central ridge of the island, whereon Appul- 

 durcombe Park extends, the Digitalis not plentiful. Mr. Thomson cruelly 

 belies the chalk when he charges it with almost a want of grasses, except 

 those allied to the bents. The fact is, that very few bents grow on chalk, 

 unless there be over the chalk a bed of poor silicious sand ; otherwise, the 



