XXVI INTRODUCTION. 



The moderate difference observable in the temperature of the 

 seasons betwixt this island and the northern parts of Britain, 

 that of summer in particular, may well appear inadequate to 

 produce so striking a contrast as we find on comparing together 

 the Floras of Newport and Edinburgh. Other^ elements, 

 scarcely less potent than temperature, here come into opera- 

 tion, to determine the balance gi'eatly in favour of the former. 

 If the heat of our summer be not very much above that of the 

 North at the same season, it is protracted into an autumn of 

 longer duration, dryness and serenity, better able to ripen the 

 vegetable tissues, and bring the seeds of plants to maturity. 

 From our proximity to the continent, and the greater breadth 

 of the mainland of England along its southern coast than else- 

 where, our atmosphere is less loaded with clouds and vapour 

 than is that over the narrow and deeply indented promontory of 

 North Britain, environed by a wide expanse of water on three 

 sides, without any adjacent surface to arrest the deposition of 

 moisture from the Atlantic, much of which is precipitated, 

 before it can reach this island, upon the peninsular counties of 

 Cornwall and Devon. Hence the amount of direct solar radia- 

 tion, so active an agent in developing a varied and vigorous 

 vegetation, is oftener and more continuously exerted here than 

 at the North, proving more equivalent in energy to the power 

 of a diffuse light, protracted through days considerably exceed- 

 ing our own in length at the season in question. 



Another peculiarity in our island Flora is the relative 

 scarcity of certain jilants characteristic of the chalk formation, 

 as compared with their abundance on the cretaceous deposits 

 of the mainland of Hampshire. We may instance Fagus syl- 

 vatica, Echium vulgare, Cichorium Intybus, and Verbascuvi 

 nigrum, which are there quite sporadic, and form no prominent 

 feature of the chalk-country vegetation. Our downs are not, 

 as there, crested with picturesque and venerable yews, of un- 

 known antiquity, their precixjitous flanks clothed vdth woods of 

 umbrageous beech, or dotted with dark compact clumps of the 

 more humble but aromatic juniper. The same jpaucity of indi- 

 viduals is observable in many other plants common to both 

 parts of the county, which, very rare or local in the Isle of 

 Wight, are of general occurrence, or at least are more plentiful 

 where they do occur, on the mainland of Hants, such as Coro- 



