Fig. 28 is the soft, grey, wool-like hair of the rat; and Fig. 29 is one of the larger hairs that protrude so plentifully, and form the glistening brown coat of that animal. Fig. 38 is the curiously knobbed hair of the long-eared bat, the knobs being formed of protuberant scales that can easily be scraped off. Fig. 31 shows a hair of the common mole; and Fig. 32 is one of the long hairs of the rabbit. Fig. 27 is a flat hair of the dormouse, slightly twisted, the difference in the breadth showing where the twist has taken place. The hair of the mouse is beautifully ribbed, so as to look like a ladder. Fig. 26 is one of the very long hairs that so thickly clothe the tiger moth caterpillar; and Fig. 25 is a beautifully branched hair taken from the common humble bee. All hairs should be examined by polarised light, with a plate of selenite, when most gorgeous colour effects may be obtained. The four fibres mostly used in the manufacture of apparel are: wool, Fig. 30, which has already been described; linen, Fig. 39; cotton, Fig. 40; and silk, Fig. 41. The structure of each is very well marked and easily made out with the microscope; so that an adulterated article can readily be detected by a practised eye. Cotton is the most common adulteration of silk and linen fabrics, and may at once be detected by its flat twisted fibre. Silk is always composed of two parallel threads, each proceeding from one of the spinnerets of the caterpillar, and it may be here remarked that if these threads are not quite parallel the silk is of bad quality. Silken fibre is always covered, when new, with a kind of varnish, usually of a bright orange colour, which gives the undressed “floss” silk its peculiar hue, but which is soluble and easily washed away in the course of manufacture. Figs. 35 and 36 are the small and large hairs of that magnificent creature, the sea mouse (_Aphrodíte aculeáta_), whose covering, although it lies in the mud, glows with every hue of the rainbow, and in a brilliant light is almost painfully dazzling to the eye. VIII.