, have their backs the
colour of the distant ground, and their bellies of the sky. In the colder
climates many of these become white during the existence of the snows.
Hence there is apparent design in the colours of animals, whilst those
of vegetables seem consequent to the other properties of the materials
which possess them.]

With chemic art _four_ favour'd youths aloof
380 Stain the white fleece, or stretch the tinted woof;
O'er Age's cheek the warmth of youth diffuse,
Or deck the pale-eyed nymph in roseate hues.
So when MEDEA to exulting Greece
From plunder'd COLCHIS bore the golden fleece;
385 On the loud shore a magic pile she rais'd,
The cauldron bubbled, and the faggots blaz'd;---
Pleased on the boiling wave old AESON swims,
And feels new vigour stretch his swelling limbs;

[_Pleased on the boiling wave._ l. 387. The story of AEson becoming
young, from the medicated bath of Medea, seems to have been intended to
teach the efficacy of warm bathing in retarding the progress of old
age. The words _relaxation and bracing_, which are generally thought
expressive of the effects of warm and cold bathing, are mechanical terms,
properly applied to drums or strings; but are only metaphors when applied
to the effects of cold or warm bathing on animal bodies. The immediate
cause of old age seems to reside in the inirritability of the finer
vessels or parts of our system; hence these cease to act, and collapse
or become horny or bony. The warm bath is peculiarly adapted to
prevent these circumstances by its increasing our irritability, and by
moistening and softening the skin, and the extremities of the finer
vessels, which terminate in it. To those who are past the meridian of
life, and have dry skins, and begin to be emaciated, the warm bath, for
half an hour twice a week, I believe to be eminently serviceable in
retarding the advances of age.]

Through his thrill'd nerves forgotten ardors dart,
390 And warmer eddies circle round his heart;
With softer fires his kindling eye-balls glow,
And darker tresses wanton round his brow.

As dash the waves on India's breezy strand,
Her flush'd cheek press'd upon her lily hand,
395 VALLISNER sits, up-turns her tearful eyes,
Calls her lost lover, and upbraids the skies;

[_Vallisniria_. l. 395. This extraordinary plant is of the class Two
Houses. It is