for when it is kept in a barrel, it corrupts in a few days; and Boyle relates that a mariner becalmed for thirteen days, found at the end of that time the sea so infected, that if the calm had not ceased, the greatest part of his people on board would have perished. The water of the sea is also mixed with a bituminous oil, which gives it a disa greeable taste, and renders it very unhealthy. The quantity of salt contained in sea water is about one-fortieth part, and the sea is nearly equally saline throughout, at the top as at the bottom, under the line, and at the Cape of Good Hope, although there are several parts, as on the Mosambique coast, where it is salter than elsewhere. It is also asserted not to be so saline under the arctic zone, which may proceed from the great quantity of snow, and the great rivers which fall into those seas, and because the heat of the sun produces but little evaporation there, in comparison of the evaporation in hot climates.

The ocean surrounds the whole earth without any interruption of continuity, and the tour of the globe may be made by passing the point of South America. Whether

the ocean surrounds the northern part of the globe in the same manner, is not yet fully ascertained; but recent discoveries afford the strongest reason to believe that such is the case. In consequence of the ice, however, all mariners who have attempted to go from Europe to China by the north-east or north-west, have alike miscarried in their enterprises.

The seas which are called MEDITERRANEAN, are proper branches from the great ocean, by which they are supplied. LAKES differ from the Mediterranean seas, because they do not receive any water from the ocean; for, on the contrary, if they have communication with the seas, they furnish them with water; thus the Black Sea, which some geographers have regarded as a connection with the Mediterranean, and consequently as an appendix to the ocean, is in reality only a lake; because, instead of receiving water from the Mediterranean, it supplies it with some and flows with rapidity through the Bosphorus into the lake called the sea of Marmora, and thence through the strait of the Dardanelles into the Grecian Sea. The water of the Black Sea appears to be less clear, and much less saline than that of the ocean. No island is to be met with throughout this sea: tempests are very violent here, and more dangerous than in the ou.

Next to the Black Sea, the greatest lake in the universe is the Caspian Sea, whose extent in length, from north to south, is about two hundred and fifty leagues, and scarcely more than eighty broad, on an average. This lake receives one of the greatest rivers in the world, i. e. the Volga; also some other considerable rivers, among which are the Yaik, the Yemba, the Daria, and the Asterabad; but what is singular is, that it does not receive any on its eastern side throughout this whole length of nearly three hundred leagues. There are some small islands in the Caspian Sea, and its waters are much less saline than those of the ocean; storms are here very dangerous, and large vessels are not used for navigation therein, as it is shallow, and many banks and shoals are scattered under the surface of the water.

There are lakes which, like pools, do not receive any river, and from which none go out. There are others which do receive rivers, and from which others run; and lastly, some which only receive rivers. The Caspian Sea and the Lake Aral, are of the last species; they receive the waters of many rivers, and contain them. Thus the Dead Sea receives the Jordan, though no river goes from it. In Asia Minor there are small lakes of the same kind. Persia has several; some of which are of great magnitude. The largest is that of Zerah, or Durra, the Aria Palus, of the ancients, which has an extent of one thousand one hundred square miles, and receives not only several minor streams, but also the river Helmund, after a course of four hundred miles. The lake of Ourmia, in Adjerbidjan, is two hundred and eighty miles in circumference; and lakes Van, Erivan, and Baktegan, are likewise of considerable size. There are also similar small lakes in Greece and Albania, and there are some of the same kind in both Africa and America. That of Titicaca, in South America, has a circumference of two hundred and forty miles, and a depth of from seventy to eighty fathoms.

The most general and largest lakes, however, are those which having received another river, or many small rivers, give rise to other great rivers. It is worthy of remark that all lakes from which rivers derive their origin, all those which fall into the course of rivers, and which carry their waters thereto, are not saline; and almost all those, on the contrary, which receive rivers, without other rivers issuing from them, are saline. which seems to favour the

opinion we have laid down on the subject of the saltness of the sea; for evaporation cannot carry off fixed salts, and consequently those which rivers carry into the sea, remain in it; and although river water appears to taste sweet, we well know that it contains a small quantity of salt, and in course of time the sea must have acquired a considerable degree of saltness, which must still continue increasing. It is thus, therefore, in all probability, that the Black Sea, the Caspian Sea, the lake Aral, the Dead Sea, &c. are become salt.

The most remarkable lake perhaps in the world, is the Dead Sea, the waters of which contain bitumen* as well as salt; this bitumen, which is called the Bitumen of India, is no other than the asphaltum, which has caused some authors to call this sea Lake Asphaltum. The land which borders on this lake contains a great quantity of bitumen, and many have applied the fables to this lake, which the poets feign of the lake Avernus, that no fish could live in it, and that birds which attempted to fly over it were suffocated: but neither of these lakes produce such mortal events; fish live in both, birds pass over them, and men bathe in them without the least danger. Such, indeed, is the specific gravity of the water, from the fluid holding in solution nearly one-fourth its weight of its various salts, that it would be difficult for a man to sink in it. A petrifying lake in Ireland is also mentioned as remarkable; and the lake Neagh, in Ireland, has also the same property of apparently turning wood, &c. into stone; but these petrifications are no other than incrustations like those made by the water of Arcueil near Paris.

CHAPTER III.

Of Winds, regular and irregular-Monsoons-Hurricanes-Whirlwinds—Waterspouts.

NOTHING is more irregular in our climates than the course of the WINDS. There are, however, countries where this irregularity does not exist, but where the wind blows constantly in one uniform direction.

finera pitch.-ED.

The theory of the winds has been so well described by Mr. Maclaren and Mr. Leslie, that we will copy their words, in preference to the vague and far less accurate description which is given by the French nai ralist. "The unequal distribution of heat over the surface of the land and water,' says Mr. Maclaren, "necessarily disturbs the equilibrium of the atmosphere, and produces currents of air or winds. These currents, however various, have been supposed to result from two general movements, pervading the whole mass of the atmosphere. The heavy and cold air of the temperate regions having a tendency to displace the warm and rarefied air of the torrid zone, generates a current in each atmosphere toward the equator. To replace the air abstracted from the higher latitudes, an upper and counter current flows back from the equator to the pole; and thus the atmosphere, while it performs a constant revolution, tempers the extremes of climate, by transporting the cold of the frigid zone to the equator, and carrying back the heat of the equator to the frigid zone. These great south and north currents, which are to be considered as the primary winds, receive various modifications. The under current, which proceeds from the polar regions, having impressed upon it the slow rotatory motion of those regions, does not acquire in its journey the velocity of the parts it passes over. Instead, therefore, of proceeding along the meridian, it is deflected to the westward. It pursues this lateral course more and more as it approaches the torrid zone, and the impulse south and north being destroyed when the currents from the opposite hemisphere meet at the equator, the motion westward alone remains. This constitutes the well known trade wind, which blows from the east at the equator, from the north-east at the northern tropic, and the south-east at the southern. The upper and counter current again, carrying with it the rapid velocity of the equatorial regions, does not trave! right along the meridian, but deviates more and more to the east as it advances; and when its progress toward the pole is topped by the accumulatien of air from the opposite meridians, the motion eastward remains, and it settles into a west wind. Thus a constant east wind should prevail at the equator, and a constant west wind near the poles; but the latter, being primarily an upper current, may not be invariably felt as a west wind at the

surface. It does not follow, however, that the upper and under currents preserve their relative situation over all the temperate zone. From the greater accumulation of air in the higher latitudes, and from variations of temperature produced by local causes, the upper current will often be beat down to the surface, and the lower current ascend. This interchange will take place occasionally at all parts of the temperate zone. Hence, in high latitudes, storms of wind, which mingle the warm upper current with the cold air below, always produce an increase of heat, as Captain Parry found. In the northern hemisphere, then, when the cold current from the pole sweeps the surface rapidly, we have north wind; it becomes a north-east wind when its motion southward is retarded; an east wind when it is checked; and a south-east when it is deflected back, by mingling with a current from the south; all of which, except the last, are generally found to be cold winds. When the warm current from the south descends and sweeps the surface, we have a south wind if its motion northward is rapid; a south-west when its motion northward is retarded; a west wind when it is checked; and a north-west when it meets and mingles with a current from the north. All these, except the last, are generally warm winds, as experience proves. The line of division between the upper and lower cur rents should be where the mercury stands at fifteen inches, which is at the height of three miles and a half. This should be the region of clouds, and clouds do generally approach to this elevation.

"The theory, upon the whole, agrees tolerably well with the facts. But the variable surface and temperature of the land greatly affect the course and velocity of the winds. In the torrid zone, within the parallel of twentyfive or thirty degrees on each side of the equator, the trade winds blow constantly from the east. From the superior warmth of the northern hemisphere, the line that separates the opposite trade winds is not the equator, but the second or third parallel north. To a certain extent also, they follow the course of the sun, reaching a little further into the south hemisphere, and contracting their limits in the north when the sun is on the south side of the equator, and making a reverse change when he declines to the north. In a zone of variable breadth, in the middle of this tract, calms and rains prevail, caused, pro