V. 
tremes of temperature are greater; an instance of this will 
appear in the tendency of some migrants to remain with 
us through the winter in years favourable to such an act ; 
equality of temperature also influences 'the geography of 
some plants, and may he suspected as the cause of the 
occurrence of some species in Devon, or in the south¬ 
western counties of England. Geography of localities 
is now better appreciated than formerly in affecting the 
precise habitats of species in both kingdoms of Nature; 
they are found to enjoy ranges and situations very differ- 
ent, according to the circumstances of their positions, as 
will appear in cases which I shall adduce in the body of 
the work. The conditions of the climate, and geography 
of localities and districts, are now understood to influence 
the periods and characters of the migrations executed b)> 
their animals ; many peculiarities of this kind, discovered 
to occur with our animals, I shall set before the reader 
likewise in the body of the following account of our 
Natural History. Constant experience enables naturalists, 
in proportion to the examination of districts, to add to 
the list of species, and, not unfrequently it happens, from 
the discovered animals or plants being far different from the 
species already known, alterations are occasioned in the 
genera, and ultimately in orders and other divisions, so as 
to affect classification generally. It will appear in the 
sequel that I have been able, through attention to the sub¬ 
ject, to add to the general catalogue, from the natural 
productions of this district. The varying characters of 
climate, food, &c. in localities, conjointly produce structu¬ 
ral differences in species exhibiting either the general 
amount of variation allotted to them, or those forms of 
