weather depend chiefly on the direction of winds, they cannot be predicted with invariable accuracy, without knowing all the circumstances which modify the temperature of different and distant places. It is not therefore surprising that meteorology has never been reduced to the certainty of an exact science.

Were it possible to compute the aggregate forces of caloric in all the mechanical, chemical, and vital transformations which are for the most part unobserved, we should be astonished at the result.* But men are so accustomed to the regular course of nature, that they are less aroused by the grandeur of the sun, rising in pomp and might, filling the world with beautiful creations, and diffusing everywhere the spirit of gladness, than by a passing meteor of the night.

That the whole theory of geological dynamics. is in some way immediately connected with the agency of caloric, is now generally admitted by

* It is in the torrid zone that nature exults in the plenitude of her powers in modifying the surface of the earth,-where the forces of the volcano, the earthquake, and of universal chemistry, are surpassed only by those which wheel the planets through their orbits. For example, we are informed by Captain Burnes, that during the Cutch earthquake of 1819, the Delta of the Indus was elevated about ten feet, over an area of fifty miles in length, and sixteen in breadth, in some places. We also learn from Mr. Lyell's excellent work on Geology, that during the shocks of 1822 in South America, the coast of Chili was raised about four feet, over an area of 100,000 square miles. And it is well known that similar movements are constantly taking place in different parts of the earth, or beneath the ocean.

philosophers. But the general fact to which I would here invite attention is, that the number of volcanos and the forces they exert are in proportion to the heating power of the sun.* For example, among the 200 volcanos now in action in different parts of the earth, about one half are confined to the tropical regions. In the island of Java alone, Mr. Lyell says there are thirty-eight and there is about the same number in other tropical portions of the old world. Between latitudes 10° and 15°, in the Provinces of Guatimala and Nicaragua in South America, there are twenty-one; while in Peru, between latitudes 14° and 20°, there are sixteen; and I know not how many in the West Indies.

Again; that the subterranean forces by which the dry land has been elevated from beneath the ocean, have in all past ages been in proportion to the heating power of the sun, would appear from the relative heights of the earth in different latitudes. Nearly the whole of tropical America

* In every point of view, a complete theory of volcanos is of fundamental importance: for they regulate the distribution of land and sea, the magnitude and elevation of continents, the diversities of temperature in given latitudes, the character of rivers, and modify the direction of winds, which are impeded or deflected by mountain ranges. They are also the great terrestrial laboratories in which most of the precious gems are formed, in which carbon is liquified, and by slowly cooling under an immense pressure, assumes the crystalline form of that beautiful ornament the diamond, which has been aptly designated as "a lump of light." Nor is it unworthy of notice, that all the richest gems and metals have been found in greatest abundance in the tropical mountains, or among the materials washed down from them by rains, rivers, and springs.

for 3,000 miles in length, and several hundred in width, is one great system of mountains, separated by plains, which, within the tropics, are from twelve to fifteen thousand feet above the sea. Near the equator, Sorato and Illimani tower to elevations of 25,400, and 24,350 feet, according to the measurements of General Pentland. As we proceed northwards towards Mexico, the loftiest peaks are those of Chuquibamba, Gualatiere, Sahama, Cotopaxi, Sierra, Antissana, and others, which vary from 19,000 to 22,000 feet, until we arrive at the table lands of Mexico, which, between latitudes 19° and 24° N. are from six to 8,000 feet above the sea.

As we advance through the middle latitudes of North America, the rocky mountains average about 10,000 feet. And if we except St. Elias and Mount Hooker, they never exceed 12,000 feet. Nor do the table lands which slope from their base exceed from three to 5,000: while it is well known that from latitude 60°, the elevations diminish on to the polar sea. On the other side of the equator, the highest mountains of Chili are the Acongagua and Descabezado, which, between latitude 32.28° and 35° S. rise to elevations of 23,200, and 21,100 feet,-from which they all diminish on to Patagonia, and thence to Cape Horn.*

It is said that Captain C. Ross has recently discovered in S. lat. 80° a mountain 12,400 feet high. But a few such exceptions are too slight to invalidate the general law.

If we turn to the old world, we shall find that there is not a single mountain chain of the first magnitude throughout the middle latitudes of Asia, Europe, New Holland, nor the islands of the sea-that, as in South America, the highest plains of India, between latitude 24° and 32°, are from twelve to 15,000 feet; while the Himalayas rise to elevations of from twenty-three to 26,862 feet-that the long chains of the Altai, which extend across Europe and Asia, in about the latitude of 50°, are generally from six to 8,000, and rarely exceed 15,000 feet:-that the mountains of western Europe also diminish in height from the Alps, the Appennines, and the Pyrenees of the south, to the Carpathians, the Dofrines, and Urals of the north; which rarely exceed 6,000 feet-that the vast plains of central Asia, between the Altai and Himalaya mountains, are from three to 5,000 feet above the level of the sea; while the plains of Siberia decline gradually on to the polar ocean :-that in Greenland and Spitzbergen the average height of the mountains is about 5,000 feet; while Hecla in Iceland is only 4,980 feet.

If the mountains of Africa are less elevated than those of southern Asia and tropical America, they are far more numerous, and the amount of high table lands is much greater than in any other quarter of the globe. Extending from the equator to 34° S. and 371 N. its central plateaus are supported by an immense chain that crosses

the continent from west to east; between which and its southern extremity, there are three other parallel ranges that diminish in height on to the Cape of Good Hope. The vast plains of Abyssinia and Nubia are also several thousand feet above the ocean, and supported by innumerable mountains of still greater magnitude than those of Atlas in the west; while the eastern coast is flanked by a chain which extends, with few interruptions, from north latitude 10° to 32° S. But it is evident that the elevation and extent of table lands, (which are in fact widely extended mountains,) afford a far more accurate measure of geological forces, than the height of a few isolated peaks.

From the foregoing brief outline we perceive, that all the highest mountains of the earth are found within 32° of the equator: and, what is still more important to observe-that the average elevation of the table lands is about equal to that of the mountains in the middle latitudes, where again, the table lands are of nearly the same height as that of the polar mountains. The conclusion is therefore irresistible, that the aggregate force by which mountains, islands, and continents, have been raised, from beneath the ocean, like all the chemical transformations on the surface of our planet, is in proportion to the heating power of the sun, ceteris paribus.

And that the same law prevails throughout the planetary system, would appear not only from