INCREASE AND DECREASE OF ANIMALS. 101 
small societies in holes under some sheltered ditch-bank. 
An old one, which I weighed, was only one dram and 
five grains in weight. 
Mankind appear to be progressively increasing. It 
was an original command of his Creator, and the animals 
domesticated by him, and fostered for his use, are 
probably multiplied in proportion to his requirements ; 
but we have no reason to suppose that this annual aug- 
mentation proceeds in a proportionate degree with the 
wild creatures upon the surface of the globe ; and we 
know that many of them are yearly decreasing, and 
very many that once existed have even become extinct. 
That there are years of increase and decrease ordained 
for all the inferior orders of creation, common observa- 
tion makes manifest. In the years 1819 and 1820, all 
the country about us was overrun with mice ; they har- 
bored under the hassocks of our coarse grasses (aira 
caespitosa), perforated the banks of ditches, occasioned 
much damage by burrowing into our potato heaps, and 
coursed in our gardens from bed to bed even during 
daylight. The species were the short-tailed meadow- 
mouse, and the long-tailed garden mouse, and both 
kinds united in the spring to destroy our early-sown 
pease and beans. In the ensuing summer, however, 
they became so greatly reduced, that few w T ere to be 
seen, and we have not had any thing like such an in- 
crease since that period. It is probable that some dis- 
ease afflicted them, and that they perished in their holes, 
for we never found their bodies, and any emigration of 
such large companies would certainly have been ob- 
served ; yet the appearance and disappearance of crea- 
tures of this kind leads us to conclude that they do oc- 
casionally change their habitations. 
A large stagnant piece of water in an inland county, 
with which I was intimately acquainted, and which I 
very frequently visited for many years of my life, was 
one summer suddenly infested with an astonishing 
number of the short-tailed water rat, none of which had 
previously existed there. Its vegetation was the com- 
mon products of such places, excepting that the larger 
portion of it was densely covered with its usual crop, 
12 
