ON THE 
PHYSICAL GEOGEAPHY OF YOEKSHIRE. 
To determine the laws which regulate the distribution of organic life 
upon the globe, is a problem requiring for its solution a precise knowledge 
of the vast variety of local conditions which interfere with the governing 
elements of climate, and modify the habitudes of plants and animals. 
Differences of soil and elevation ; unequal exposure to light, air and the 
vapours of fresh or salt waters ; these, and many other circumstances, 
predominate over the general influence of temperature, and enable the 
productions of different latitudes to flourish side by side in a narrow 
region of the surface of the earth. Moreover, if due allowance can be 
made for all these causes of local difference and resemblance, there still 
remain, both in botany and zoology, multitudes of facts not in this man- 
ner explicable; solitary groups of plants in the recesses of the mountains; 
peculiar shells and fishes in the streams ; birds and insects self-confined 
in limited tracts of the air. 
It would be too much to expect in a local fauna or flora more than 
a small contribution toward the knowledge of the distribution of plants 
and animals ; yet it is upon the evidence contained in such local surveys 
alone that comprehensive inferences can be securely founded. In them 
the philosophic contemplator of nature ought to find exact if not com- 
plete data for correct reasoning ; and if the districts be well chosen, not 
too limited in area, nor too uniform in physical constitution, conclusions 
of general value may be safely proposed upon an adequate basis of 
observed facts. Yorkshire is such a district, and if in this little work we 
have not ventured far in a path which requires much Philosophical as 
b 
