A remarkable instance of sagacity in a long-tailed Field Mouse (_Mus sylvaticus_) occurred to the Rev. Mr. White, as his people were pulling off the lining of a hotbed, in order to add some fresh dung. From the side of this bed something leaped with great agility, that made a most grotesque appearance, and was not caught without much difficulty. It proved to be a large Field Mouse, with three or four young ones clinging to her teats by their mouths and feet. It was amazing that the variousand rapid motions of the dam did not oblige her litter to quit their hold, especially when it appeared that they were so young as to be both naked and blind. Mr. White appears to be the first to describe and accurately examine that diminutive creature the Harvest Mouse (_Mus messorius_) the least of all the British quadrupeds. He measured some of them, and found that from the nose to the tail they were two inches and a quarter long. Two of them in a scale only weighed down one copper halfpenny, about the third of an ounce avoirdupoise! Their nest is a great curiosity, being made in the form of a ball, and either suspended between the stems of rushes and other tall slender plants, or placed amongst the leaves of some large thistle. [Illustration: THE RAT. (_Mus decumanus._)] THE RAT is about four times as large as the mouse, but of a dusky colour, with white under the body; his head is longer, his neck shorter, and his eyes comparatively larger. These animals are so attached to our dwellings, that it is almost impossible to destroy the breed, when they have once taken a liking to any particular place. Their produce is enormous, as they have from ten to twenty young ones at a litter, and this thrice a year. Thus their increase is such, that it is possible for a single pair (supposing food to be sufficiently plentiful, and that they had no enemies to lessen their numbers) to amount at the end of two years to upwards of a million; but an insatiable appetite impels them to destroy each other; the weaker always fall a prey to the stronger; and the large male Rat, which usually lives by itself, is dreaded by those of its own species as their most formidable enemy. The Rat is a bold and fierce little animal, and when closely pursued, will turn and fasten on its assailant. Its bite is keen, and the wound it inflicts is painful and difficult to heal, owing to the form of its teeth, which are long, sharp, and of an irregular form. It digs with great facility and vigour, making its way with rapidity beneath the floors of our houses, between the stones and bricks of walls, and often excavating the foundations of a dwelling to a dangerous extent. There are many instances of their totally undermining the most solid mason-work, or burrowing through dams which had for ages served to confine the waters of rivers and canals.