between the second and fifth degrees of north latitude is the internal boundary of the two winds; and this space experiences calms, frequently interrupted, however, by violent storms. The reason why it is situated to the north of, instead of exactly at, the equator, seems to be, that the northern hemisphere is warmer than the southern; for, since the trade-winds are the result of the continual ascent of heated air in the equatorial parts, their internal boundary will be where the principal ascent is going on, that is, where the annual temperature is the highest, which, on account of the above-mentioned inequality of temperature in the two hemispheres, will not be at the equator, but somewhat to the north of it. The external limits of the trade-winds are, at a medium, in about the thirtieth degrees of north and south latitude respectively; but each limit, as the sun approaches the neighboring tropic, declines farther from the equator. The position of the sun has an influence, also, on their strength and direction; for, when that luminary is near the tropic of Cancer, the south-east wind becomes gradually more southerly, and stronger, and the north-east weaker, and more easterly. The effect is reversed when he gets towards the tropic of Capricorn. The trade-winds would blow regularly round the whole globe within the distance of about thirty or forty degrees from the equator each way, if the space within those limits were all covered with water; but the uneven surface and unequal temperature of the land divert and derange them. It is on this account that the trade-winds are constantly experienced only over the open ocean. The larger the expanse of ocean over which they range, the more steadily they blow; thus, in the Pacific, they are commonly more steady than in the Atlantic ocean, and in the South than in the North Atlantic. In sailing from the Canaries to Cumana, on the north coast of South America, it is hardly necessary to touch the sails of the vessel. The voyage across the Pacific, from Acapulco, on the west coast of Mexica, to the Philippine islands, is performed with equal facility; and, if there were a channel through the isthmus of Panama, a westward passage from the Atlantic to China would be more speedy and safe than the usual navigation thither round the cape of Good Hope. The only interruption to the evenness of this voyage would be in the Caribbean sea and the gulf of Mexico, where the trade-wind blows impetuously, and is sometimes interrupted

by westerly winds. It would not be possible, however, to return by the same route, because, in sailing east, way must be made to the northward, in order to get beyond the region of the trade into that of the variable winds. Both in the Atlantic and in the Pacific ocean, the current of the trade-winds becomes broader, and more directly east in its course, as it advances from one side to the other of those extensive basins. On the west coast of Africa, owing to the rarefaction which the air undergoes over that continent, the wind is mostly turned towards the shore: from cape Bojador to cape Verde, it is generally north-west, and thence to the island of St. Thomas, under the equator, it bends gradually, first to the west, and then to the south-west. Along the coasts of Chile and Peru, a south wind prevails. These are two instances of the interruption which the trade-winds experience in the neighborhood of large masses of land. In the Indian ocean, the south-east tradewind prevails between 28° and 10° of south latitude, from within a few degrees of the east side of Madagascar, nearly to the coast of New Holland; but, from the tenth degree of south latitude to the northern shores of that ocean, the uniformity of the tropical movements of the atmosphere is destroyed by the monsoons (q. v.), which belong to the class of periodical winds. These blow half the year from one quarter, and the other half from the opposite direction. When they shift, variable winds and violent storms prevail for a time, which render it dangerous to put to sea. They, of course, suffer partial changes in particular places, owing to the form and position of the lands, and to other circumstances; but it will be sufficient to give their general limits and directions. Northward from the third degree of south latitude, a south-west wind blows from April to October; from October to April, a north-east. These monsoons extend over the China sea; but here they incline more to the direction of north and south. Between the third and tenth degrees of south latitude, a north-west wind blows from October to April, and a south-east during the other six months of the year: the former is seldom steady in the open sea; but, in December and January, it sometimes extends northward a degree or two beyond the equator. These two monsoons have the greatest strength and regularity in the Java sea, and thence eastward towards New Guinea. The facts above exhibited may be thus summed up: From April to October a south

west wind prevails north of the equator; southward of this, a south-east wind: from October to April, a north-east wind north of the equator, and a north-west between the equator and 10° of south latitude; south of this, the usual trade-wind, which is in motion through the whole year. In attempting to account for these movements of the atmosphere over the Indian ocean, the first thing which strikes us is, that the north-east and south-east monsoons, which are found the one on the north and the other on the south side of the equator, are nothing more than the trade-winds blowing for six months, and then succeeded, for the remainder of the year, by winds directly opposite. It is also to be noticed that the south-west monsoon in the northern, and the northwest monsoon in the southern, hemisphere, each prevails while the sun is perpendicular to their respective regions. They are, therefore, connected with the immediate presence of that luminary. If the Indian ocean were not bounded, as it is, by land on the north, the trade-winds would blow over it (at least in the central parts) as they do in the Atlantic and Pacific oceans. But it is well known that water, owing to its transparency, is very little warmed by the sun's rays, whereas the land is powerfully heated by them; consequently, when the sun is between the equator and the tropic of Cancer, India, Siam, and the adjacent countries, become much hotter than the ocean; the air over them is rarefied, and ascends: colder air then rushes in from the Indian ocean, and a south-west wind is produced. When the sun, however, has crossed to the south of the equator, these countries become gradually cool, and the northeast trade-wind resumes its course. At the same time, the north-west monsoon commences in the southern hemisphere, in consequence of the air over New Holland being rarefied by the presence of the sun. The monsoons in the Red sea blow in the direction of the shores; and a similar effect is observed in the Mozambique channel, between Africa and Madagascar, where these winds follow the line of the channel. On the coast of Brazil, between cape St. Augustine and the island of St. Catharine, and in the bay of Panama, on the west of the isthmus of that name, periodical winds occur somewhat similar to the monsoons of Asia. The land and sea-breezes, which are common on coasts and islands situated between the tropics, are another kind of periodical winds. During the day, the air over the land is

strongly heated by the sun, and a cool breeze sets in from the sea; but, in the night, the atmosphere over the land is cooled, while the sea, and, consequently, the air over it, retains a temperature nearly even at all times; accordingly, after sunset, a land-breeze blows off the shore. The sea-breeze generally sets in about ten in the forenoon, and lasts till six in the evening. At seven, the land-breeze begins, and continues till eight in the morning, when it dies away. These alternate breezes are, perhaps, felt more powerfully on the coast of Malabar than elsewhere. Their effect there extends to a distance of twenty leagues from the land. During summer, the sea-breeze is very perceptible on the coasts of the Mediterranean, and sometimes even as far north as Norway. We thus perceive that, within the limits of from twenty-eight to thirty degrees on each side of the equator, the movements of the atmosphere are carried on with great regularity; but, beyond these limits, the winds are extremely variable and uncertain, and the observations made have not yet led to any satisfactory theory by which to explain them. It appears, however, that, beyond the region of the trade-winds, the most frequent movements of the atmosphere are from the south-west in the north temperate zone, and from the north-west in the south temperate zone. This remark must be limited to winds blowing over the ocean, and in maritime countries; because those in the interior of continents are influenced by a variety of circumstances, among which the height and position of chains of mountains are not the least important. These south-west and northwest winds of the temperate zones are most probably occasioned in the following manner: In the torrid zone, there is a continual ascent of air, which, after rising, must spread itself to the north and south in an opposite direction to the tradewinds below. These upper currents, becoming cooled above, at last descend and mix themselves with the lower air: part of them may perhaps fall again into the trade-winds; and the remainder, pursuing its course towards the poles, occasion the north-west and south-west winds of which we have been speaking. It has also been conjectured that these winds may frequently be caused by a decomposition of the atmosphere towards the poles, from part of the air being at times converted into water. (See Hurricane, Whirlwinds, Harmattan, Simoom, &c.) The following facts, illustrative of the

velocities of the sail and the wind must both be taken into account; for, if the sail moved before the wind with a speed equal to that of the wind itself, no effect would be produced. The effect will depend on the difference of the velocities, that being the velocity with which the wind strikes the sail. Now, as the obliquity of the sail to the wind should depend on the force with which the wind acts upon it, and as those parts of the sail which are nearer to the centre of motion move more slowly than those which are more remote, it follows that the position of the sail should vary at different distances from the centre of rotation. From the experiments of Mr. Smeaton on this subject (Philosophical Transactions, 1759), appears that the following positions are the best. Suppose the radius to be divided into six equal parts, and call the first part, beginning from the centre, one, the second two, and so on, the extreme part being six:

it

As it is necessary that a windmill should face the wind from whatever point it blows, the whole machine, or a part of it, must be capable of turning horizontally. Sometimes the whole mill is made to turn upon a strong vertical post, and is therefore called a post mill; but, more commonly, the roof or head only revolves, carrying with it the windwheel and its shaft, the weight being supported on friction rollers. In order that the wind itself may regulate the position of the mill, a large vane, or weathercock, is placed on the side which is opposite the sails, thus turning them always to the wind. But in large mills the motion is regulated by a small supplementary windwheel, or pair of sails, occupying the place of the vane, and situated at right angles with the principal windwheel. When the windmill is in its proper position, with its shaft parallel to the wind, the supplementary sails do not turn. But when the wind changes, they are immediately brought into action, and, by turning a series of wheelwork, they gradually bring round the head to its proper position. Adjustment of Sails. On account of the inconstant nature of the motion of the

wind, it is necessary to have some provision for accommodating the resistance of the sails to the degree of violence with which the wind blows. This is commonly done by clothing and unclothing the sails; that is, by covering, with canvass or thin boards, a greater or smaller portion of the frame of the sails, according to the force of the wind at different times. A method has been devised for producing the same effect, by altering the obliquity of the sails; and windmills have been so made as to regulate their own adjustment by the force of the wind. If we suppose a windmill, or windwheel, to consist of four arms, and that the sails were connected to these arms at one edge by means of springs, the yielding of these springs would allow the sails to turn back when the wind should blow with violence; and their elasticity would bring them up to the wind whenever its force abated. This effect has been produced by a weight acting on the sails through a series of levers. A loose iron rod, passing through the centre of the axle of the windwheel, receives the action of the weight at one end, and communicates it to the sails at the other.

WINDPIPE (trachea); a cartilaginous and membranous canal, through which the air passes into the lungs. Its upper part, called the larynx, is composed of five cartilages, the uppermost of which, called the epiglottis (q. v.), closes the passage to the lungs, when a person is in the act of swallowing. The two front cartilages of the larynx, the thyroides, or Adam's apple, and the annular, which resembles a ring, may be felt directly under the skin. The various cartilages of the larynx are united to each other by elastic fibres, and are enabled, by their several muscles, to dilate or contract the passage, and perform those numerous motions which render the larynx so important as an organ of the voice; for, when the air passes directly into the trachea through a wound, it produces little or no sound. (See Voice.) From the larynx the canal takes the name of trachea, and, after extending as far down as the fourth or fifth vertebra, it divides into two branches, running to the two lobes of the lungs (q. v.), to which they are distributed by an infinite number of branches. The trachea is furnished with muscular fibres, by the contraction or relaxation of which it is enabled to shorten or lengthen itself, and also to dilate or contract the diameter of its bore. The cartilages of the trachea, by keeping it constantly open, afford a

free passage to the air, which we are obliged to be incessantly respiring; and its membranous part, being capable of contraction or dilatation, enables us to receive and expel the air in a greater or less quantity, and with more or less velocity, as may be required in singing and declamation. (See Respiration. For the structure of the windpipe in birds, see Ornithology.) This membranous structure of the trachea posteriorly, seems likewise to assist in the descent of the food by preventing that impediment to its passage down the oesophagus, which might be expected if the cartilages were complete rings.

WIND SAILS, in a ship, are made of the common sail-cloth, and are usually between twenty-five and thirty feet long, according to the size of the ship, and are of the form of a cone ending obtusely. When they are made use of, they are hoisted by ropes to about two thirds or more of their height, with their bases distended circularly, and their apex hanging downwards in the hatchways of the ship. Above each of these, one of the common sails is so disposed that the greatest part of the air, rushing against it, is directed into the wind sail, and conveyed into the body of the ship, to promote ventilation, &c.

WINDERMERE; a celebrated lake in the county of Westmoreland, the most extensive sheet of water in England. It is situated at the foot of the Furness fells, and is distinguished by the variety of beautiful prospects which it exhibits. It is about fifteen miles in length from north to south, and about one broad on an average, though in many places much less. WINDHAM, Sir William. (See Wyndham.)

WINDHAM, William. (See Appendix.) WINDOW. In the most ancient eras, the windows of habitations were very small and narrow; and the same remark is true of the castles and other edifices which were constructed during the middle ages. In the painting on the Greek vase which represents Jupiter about to scale the window of Alcmena, the opening is exceedingly small. According to Seneca, those of the baths of Scipio were so small that they merited not the name, and might rather be denominated crevices. As the Romans improved, however, in the elegant arts, this particular was not overlooked; and both their town and country houses were decorated with numerous and ample windows. It was not customary to have

them overlooking the street; and they were, in the majority of instances, confined to the interior court of the house. The ancient temples had not, generally, windows: some exceptions, however, exist to this observation. Before the use of glass became common, which was not till towards the end of the twelfth century, the windows in England seem generally to have been composed of paper, which, properly prepared with oil, forms no contemptible defence against the intrusions of the weather, and is a tolerable medium for the admission of light. In warm climates, as in the West Indies, windows are often quite open, without glass or any translucent medium to admit light while it excludes the air. In Russia, salt is used to clean windows from frost, on account of its effect in liquefying this substance. It is rubbed on the glass with a sponge. In England, windows are one of the articles subjected to taxation.

The

WINDSOR, the capital of Hants county, Nova Scotia, is situated on the Avon and the St. Croix, just above their junction, forty-five miles north of Halifax. After the Avon receives the St. Croix, it spreads into a wide frith, and afterwards flows into the basin of Minas. The rise of the Avon at Windsor is twenty feet at neap tides, and thirty at spring tides. river at low water is only a brook. Windsor has a fine situation, and contains some of the best land in the province. Its principal commercial business arises from its gypsum. This is carried, in great quantities, to St. John's, in New Brunswick, to be shipped thence to the U. States. In 1828, Windsor contained a university, an academy, a court-house, a jail, and houses of worship for Episcopalians, Roman Catholics, Methodists, Presbyterians and Baptists; and 2065 inhabitants. The charter of the university bears date May 12, 1802. The first degrees were conferred in 1807. The number of students is small. The college contains a good library and a valuable philosophical apparatus. The institution is liberally endowed. There is a collegiate school or academy subordinate to the university. This seminary is in a flourishing state.

WINDSOR; a post-town of Windsor county, Vermont, situated on the west bank of the Connecticut, eighteen miles south of Dartmouth college, and sixty-one south of Montpelier; lat. 43° 29′ N.; lon. 72° 30′ W.; population in 1820, 2956; in 1830, 3134. It is a pleasant town, and