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 augmentation 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 observation makes manifest. In the years 1819 and 1820, all the country about us was overrun with mice; they harbored under the hassocks of our coarse grasses (aira cæspitosa), 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 were to be seen, and we have not had any thing like such an increase since that period. It is probable that some disease 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 observed; yet the appearance and disappearance of creatures of this kind leads us to conclude that they do occasionally 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 common products of such places, excepting that the larger portion of it was densely covered with its usual crop, the smooth horsetail (equisetum limosum). This constituted the food of the creatures, and the noise made by their champing it we could distinctly hear in the evening at many yards’ distance. They were shot by dozens daily; yet the survivors seemed quite regardless of the noise, the smoke, the deaths, around them. Before the winter, this great herd disappeared, and so entirely evacuated the place, that a few years after I could not obtain a single specimen. They did not disperse, for the animal is seldom found in the neighborhood, and no dead bodies were observed. They had certainly made this place a temporary station in their progress from some other; but how such large companies can change their situations unobserved in their transits, is astonishing. Birds can move in high regions and in obscurity, and are not commonly objects of notice; but quadrupeds can travel only on the ground, and would be regarded with wonder, when in great numbers, by the rudest peasant.[40]