4 ON THE LAW WHICH HAS REGULATED 
acquainted, or has been able to observe himself. 
These have all served to convince him of the correct- 
ness of his hypothesis. Fully to enter into such a 
subject would occupy much space, and it is only in 
consequence of some views having been lately pro- 
mulgated, he believes, in a wrong direction, that he 
now ventures to present his ideas to the public, with 
only such obvious illustrations of the arguments and 
results as occur to him in a place far removed from 
all means of reference and exact information. 
A Law deduced from well-known Geographical and 
Geological Facts. 
The following propositions in Organic Geography 
and Geology give the main facts on which the 
hypothesis is founded. 
Geography. 
1. Large groups, such as classes and orders, are 
generally spread over the whole earth, while smaller 
ones, such as families and genera, are frequently 
confined to one portion, often to a very limited dis- 
trict. 
2. In widely distributed families the genera are 
often limited in range; in widely distributed genera, 
well marked groups of species are peculiar to each 
geographical district. 
3. When a group is confined to one district, and 
is rich in species, it is almost invariably the case 
that the most closely allied species are found in the 
same locality or in closely adjoining localities, and 
