nice adjustment and gentle vicissitudes of heat and cold, which attend the returns of day and night, and summer and winter; and that even the form, under which it and the other elements play their parts, depends upon the limited action of heat. Were our heat to be diminished, and to continue diminished, to a degree not very far below the ordinary temperature, the water would lose its fluidity, and assume the form of a solid hard body, totally unfit for the numerous purposes which it serves at present. And, if the diminution of heat were to go still farther, the air itself would lose its elasticity, and would be frozen to a solid useless matter like the water; and thus all nature would become a lifeless, silent, and dismal ruin."-" On the other hand, were the heat which at present cherishes and enlivens this globe, allowed to increase beyond the bounds at present prescribed to it; beside the destruction of all animal and vegetable life, which would be the immediate and inevitable consequence, the water would lose its present form, and assume

28

that of an elastic vapour like air; the solid
parts of the globe would be melted and
confounded together, or mixed with the air
and water in smoke and vapour ; and nature
would return to the original chaos*"

The effects of heat afford an inexhaustible
subject for discussion: but it does not form
part of my plan, in this general view, to
enter largely into it.
marking one of those effects, however, be-
I cannot avoid re-
cause of its extensive agency and use in the
creation, as giving origin to the winds.

The heat of the sun appears to be the
most powerful cause of winds; and, amongst
the innumerable beneficial consequences
arising from their agency, there is one ex-
ceedingly interesting to the Naturalist, as
explaining some difficult and very curious
phænomena. Besides their utility in pre-
venting the general stagnation, and conse-
quent putridity, of the atmosphere; they
are employed in wafting the productions of
one country to another, and in clothing

* Lectures on the Elements of Chymistry, vol. i. p. 247.

the earth, even to the otherwise inaccessible heights of rocks and mountains, with vege tation. The seeds of innumerable plants are furnished with wings, and feathery ap pendages, expressly to qualify them for distant flight by these means. Thus, wherever the smallest accumulation of soil takes place, whether on the craggy summits of mountains, the little chinks and clefts on the sides of rocks and precipices, or even on the tops of lofty edifices raised by man, we perceive attempts made to establish the vegetable kingdom. Myriads of seeds are wafted by these means, in every direction, over the whole surface of the earth and sea, --but those only take root, and spring up, which happen to fall on a spot suited to their growth. Even when subterranean fires break out in the bottom of the ocean, and, by volcanic power, cast up new islands, far distant from any former land, those desolate spots soon become clothed with a vegetable mantle, and their nakedness is no longer terrible to the wandering tribes of animals

which occasionally gather round their shores.

In the middle solitude of the vast Indian Ocean there exists an island of this volcanic origin, at the sublime distance of more than two thousand miles from any other land; which, in remote ages, hath arisen in tremendous noise and combustion from the unknown depths of the sea, and which, from its topmost height, still breathes forth sulphureous vapour, and smoke, and flame. It has been called the Island of Amsterdam*. Had BARROW, the well known and enlightened traveller, been generally acquainted with the Philosophy of Natural History, he would not have found himself so much at a loss to account for the clothing of the greater part of this extraordinary island with a rich

* It is surrounded by very lofty and wall-like precipices, and is about twelve miles in circumference; it abounds with hot springs, and is covered with a great variety of plants and animals,--altogether presenting an highly curious and interesting object to the traveller, and the naturalist.

and plentiful vegetation *. He would have immediately perceived that the germes of vegetation must have floated to that solitary spot on the wings of the wind; and, if any doubt of that fact could obtain in his mind, the circumstance of there being no plant so high as a shrub, nor any that could be deemed frutescent, on the whole island; as well as the remarkable fact that the naturalist of the expedition actually collected more than fifteen genera known to be natives of Europe on various parts of its surface; might have removed any such doubt, and confirmed the truth of this bypothesis.

From what has already been observed, some idea may be formed of the amazing extent of the field for investigation opened to an inquiring mind by the subject of heat: and, of all foolish idolaters, or simple worshippers, those who fall down in adoration

*See his Voyage to Cochin-China in the years 1799 and

1793