of steel is attached by its extremities to the ends of the two shafts, as shown in Figs. 2 and 3. The diameter of the spiral, in order to secure strength, is made considerably larger than that of the shaft, and the attachment to the shaft is made by means of a cast-iron cap, having on one side a socket for the shaft, and on the other a flat surface to receive the spiral. The diameter and breadth of the spiral will vary with the power of the mill or the maximum spread of sail, but the thickness cannot be indefFIG. 4.

initely increased, since the cross-strain upon the metal would be too great. The thickness commonly used is about a quarter of an inch; the diameter, for mills of moderate power, one foot; and the breadth about an inch and a half. These joints operate very well, and are very durable.

The disadvantage attendant on a change of direction of the axis of rotation, by whatever means the transmission of movement is effected, has led to the use, in some cases, of horizontal windmills, in which the sails are placed at the extremities of arms radiating horizontally from a vertical shaft. By employing a cylindrical frame so as to secure the sails at both extremities, any vertical dimensions may be given them that may be desired; but if the sails are plane and immovable, and coincide in direction with the radii, the machine will not rotate unless one-half of it is screened from the wind. If the sails are hemispherical cups or cones, with the concavities set in a common direction along the circumference, the effective pressure of the wind will be more than twice as great on the concave as on the convex sides, and rotation will take place. But this form of sail is not of simple construction, and is not used for windmills, though we see it in anemometers. There were formerly in New York City two or three horizontal windmills, in which the sails were plane panels of wood hinged to a light cylindrical frame by a vertical edge, and free to swing through an arc of 180°. In passing the point of the revolution opposite the direction of the wind, the sail swung outward, and presented its edge to the wind during the succeeding half revolution; in consequence of which it was made gradually to swing inward, so that in passing the point toward the wind it was pressed against the radii of the frame and held in proper position to be effective. A more recent form of horizontal FIG. 6.

tion to the radii, the whole rotating frame being then enclosed within a similar fixed structure, which the wind enters through openings between boards set at an obliquity contrary to that of the sails or floats. With this construction the mill is effective from whatever direction the wind may blow. The best form of windmill of this construction is that of Moerath of Vienna, Austria, which, from the peculiar form of its sails, may be called an aërial turbine. This is shown in Figs. 4, 5, 6, and 7, Fig. 4 being an elevation representing the interior of a circular structure designed to enclose the frame or wheel carrying the sails. The rotation takes place about the central axis L. The form of the sails is exhibited in Fig. 5, which also shows, in plan, a series of fixed directrices, ab, a'b', by which the currents of the air, coming in the direction indicated by the arrows, are deflected upon the sails. These sails are of canvas, for the sake of lightness, but their form is determined by the iron arms or frames to which they are attached. These frames are secured at top and bottom to two circular plates which are fixed to the axis. Beneath the whole there is also attached to the axis a pulley which, by means of guide-rollers, represented at K (Figs. 4 and 5), maintains it in position. The weight is sustained and the level more truly preserved by means of the rollers S, Fig. 4, themselves resting by their axes upon the smaller friction-rollers & s'. The guiding wheels Kare sustained by brackets from the frame, shown at G in both figures. The power is applied through conical gearing, as shown at m or a, or in any other way.

The structure on which the motor rests may be of wood, brick, or stone; but the chamber in which the wheel is placed is designed to be constructed of iron, except the roof. Its base H (Fig. 4) forms a cast-iron crown, to which are bolted the brackets G, and from which rise vertically, at regular intervals, a series of rolled iron plates, which form the directrices for the wind, and also the support for the superstructure. It will be seen, by comparing the positions of the directrices in the plan with the directions of the arrows, that on the side on which the wind and wheel move in harmony, the wind can enter until its direction becomes tangential to the structure; while on the other side it is cut off from entering at all by the overlapping of the borders of the directrices, up to the point where it becomes capable of such a deflection as to favor rotation. A very ingenious provision is made for guarding against excessive velocity of movement in the case of high winds. To every one of the directrices there is attached, on the outside, a shutter wide enough to close entirely one of the openings, but pivoted by the middle points of its extremities, so that instead of closing one opening entirely, it closes the adjacent halves of the two between which it is placed. Thus, when all the shutters are closed, they meet each other halfway, like the blinds of windows. In the plan, Fig. 5, these shutters are seen at ed, c'd'. In calm or in light winds they stand in the positions in which the figure represents them. But when the velocity of movement begins to rise above what is designed to be the limit, they are closed to a greater or less extent by the effect of a self-acting apparatus represented in Fig. 4, and on an enlarged scale in Fig. 6, and through a system of connectingrods shown in Fig. 7. The main axis of rotation L carries a gear-wheel r, which acts on the governor, Fig. 6, through the smaller wheel r', secured to the vertical axis of the governor. By the divergence of the arms of the governor the doubly-conical friction-wheel y is raised, and is brought at length to the point where its upper conical surface is in contact with the conical wheels Z and z. The wheel Z is fixed to its shaft and operates the conical gear-wheels t. The wheel z is idle, its use being merely to equilibrate the pressure. The vertical conical wheel t turns the tangent screw f, which rests on the perimeter of a large wheel, seen dotted in the plan of this part of the machine, Fig. 7. To this wheel x are attached a number of rods, equal to the number of shutters; and these rods, by their opposite extremities, are fastened by hinge-joints to the outer extremities of the shutters, severally. An examination of the plan will show that if the wheel x be turned from right to left, the shutters will be drawn inward, and if the movement be sufficiently continued, they will be closed entirely. The action of the wheel Z upon the wheel x through the tangent screw turns it from right to left, and thus by the automatic action of the machine itself the shutters are partially closed and the impelling force diminished. velocity diminishing, the friction-wheel y will descend, and Z will cease to act. If, in consequence of the reduction of the driving force, the retardation is in excess, the friction-wheel y will descend until it comes into contact with Z' and z', of which the first is now idle, and the second turns the bevel-wheel t', reversing the motion of the gear-wheel z, and to a greater or less extent reopening the air-passages. There may thus take place a succession of oscilla

The

583

tions of the bevel-wheel y, diminishing in extent if the breeze remains steady, until a permanent adjustment is attained. But if the wind varies, whether by an increase or a diminution of its mean velocity, the bevel-wheel y will act anew and effect a new adjustment corresponding to the changed velocity. It is not to be understood that the wheel a will be acted upon in response to every momentary lull or gust, since the bevel-wheel y has a sufficient freedom of movement between Z and Z' to accommodate itself to these, so long as the average strength of the wind remains unchanged. But if there is a permanent increase or diminution of the wind-force, the necessary correction will be made with infallible certainty.

The governor can be thrown out of gear with the machine; and if it is desired to leave the mill at rest, the wheel x, after detaching the governor, may be turned by hand so as to close the shutters entirely. It is an important recommendation in favor of this form of windmill that it is not liable to damage by the most violent storms.

There are large portions of our country in which windmills are almost unknown. There are other portions, as in California, where they are extensively used, and where objects of this class frequently strike the attention of the traveller. They would be undoubtedly much more generally introduced if, in their ordinary forms, they were less rude and more efficient. They adapt themselves admirably to the circumstances of sparse settlements, in prairie districts and low alluvial regions, where streams are few and sluggish, where fuel is costly, and where the population, chiefly engaged in the cultivation of the soil and living in comparative isolation from each other, find the conversion of their grains into flour and meal for domestic uses a serious tax upon both their time and their means. To such, a mill like that just described would be very useful for the elevation of water, for drainage, for grinding, and for many of the other exigencies of rural life. F. A. P. BARNARD.

Win'dom, cap. of Cottonwood co., Minn. (see map of Minnesota, ref. 11-G, for location of county), on Chicago St. Paul Minneapolis and Omaha R. R., 150 miles from St. Paul, has a handsome park, fine water-power, large gradedschool building, butter-packing establishment, etc., and is the centre of a large dairying and farming community. P. in 1880, 443; in 1885, 641.

Windom (WILLIAM), b. in Belmont co., O., May 10, 1827; studied law, and entered upon the practice of his profession in Ohio; removed to Minnesota in 1855; member of Congress 1858-68: appointed U. S. Senator July, 1870, to fil a vacancy, and elected Senator for 1871-77; re-elected in 1876; was U. S. Secretary of Treasury Mar. 5, 1881, to Oct. 27, 1881; re-elected U. S. Senator Oct. 26, 1881, for term ending 1883.

Win'dow-pane, so called on account of its thin, transparent body, a name given on parts of the N. American coast to the Lophopsetta maculata, which is most nearly related among American fishes, to the turbot of Europe.

Wind'pipe, or Air-passage, the popular name of the trachea, so called from its roughness [Gr. τpaxús,

The Trachea.

"rough"], a cylindrical tube of cartilage and membrane, 44 inches long and from to 1 inch in diameter, extending

from the larynx (see LARYNX), downward to the origin of the two primary bronchial tubes. These branch off from the trachea opposite to the third dorsal vertebra, one going to each lung. The ancients termed the trachea aspera arteria, the great artery or channel by which the vital air was inspired; air was supposed to fill the arteries and veins, the nutritive agency of the blood being unknown and its circulation undiscovered. The trachea is an open tube, its collapse being prevented by its cartilaginous circular bodies or rings. These are incomplete, the posterior wall of the trachea being membranous, flaccid, and flat. This soft surface rests against the oesophagus, the food-passage, and facilitates the ingestion of food. The trachea is often the seat of catarrh and acute inflammation, during the progress of colds, influenza, and the incipient stages of bronchitis, from the mucous membrane of the nose and throat to the lungs. The trachea is occasionally the seat of croupous membrane (see CROUP and TRACHEOTOMY), of foreign bodies, polypus, cancer.

E. DARWIN HUDSON, JR. REVISED BY WILLARD PARKER. Winds, or Vinds. See SLOVENTZI.

Winds. Wind is air in motion. The word is usually applied to currents of air more or less horizontal, though vertical or slanting currents of air, whether ascending or Winds are named descending, equally deserve the name. from the quarter of the horizon from which they come. Thus a wind blowing from E. to W. is an E. wind; one moving from N. to S. is a N. wind. The direction of the surface-winds can easily be taken from a wind-vane so located as to be free from all surrounding obstacles. For the direction of the winds in the upper part of the atmosphere, which is often very different from that of the surfacewinds, we have to look to the course of the clouds. The winds from the four cardinal points, north, east, south, and west, and those from the intermediate directions, designated as north-east, south-east, south-west, and north-west, are the eight principal winds usually noted in meteorological journals, and are indicated simply by their initials. Further intermediate directions give eight more windsviz. north-north-west and north-north-east on either side of north; south-south-west and south-south-east on either side of south; west-north-west and west-south-west on either side of west; and east-north-east and east-south-east on either side of east. For the use of mariners the divisions are carried to thirty-two winds. (See COMPASS.) When greater accuracy is needed, however, it is more convenient to use the division of the circle of the azimuth compass, and, starting from one of the cardinal points, note how many degrees from it, on either side, the radius passes which indicates the direction of the wind; as, for instance, north 25° east, south 15° east, and so on. A diagram constructed like the mariner's compass, bearing the name of the winds, is called the wind-rose. By giving to the radius representing each wind a length proportional to the length of time and the velocity with which it has blown at a given place during a stated period, such as a year or a month, a wind-rose may be traced which will present at a glance the peculiar condition of this important element of climate at that place. In the two following diagrams, for instance, which represent in this way the average duration of winds in January and July in Maryland, the eye seizes at once FIG. 1.

the great prevalence of the north-westerly winds in winter and of the south-westerly in summer which is characteristic of the climate of the Atlantic coast. Prof. Dove of Berlin has used a similar method for showing graphically the average condition of the barometric pressure, thermometer, and hygrometer which accompanies the different winds, and calls such diagrams the barometric, thermic, and atmic (hygrometric) wind-roses of the places considered. The velocity and force of winds vary from an almost inappreciable breath of air to the furious hurricane which sweeps everything before it. It is measured by means of the anemometer ("wind-measure"), an instrument of which various kinds have been invented. (See ANEMOMETER.) Some give the pressure exerted by the wind upon a spring, like those of Osler and Jelineck, or on a liquid contained in a glass tube having the shape of a siphon, like that of

Lind; others derive the velocity from the number of revolutions of a self-registering rod set in motion either by a vertical wheel composed of oblique plates, like that of a windmill, as in the anemometers of Wolfe and Whewell, or by four hemispherical cups placed horizontally, catching the wind, as in that of Robinson. The last form has been adopted by the Smithsonian Institution and the U. S. Signal Service. In all these instruments the velocity has to be computed by formulas based on previous experiments. It is on such trials that the various scales proposed to express the force and velocity of winds are founded. The scale adopted by the Smithsonian Institution, which is almost identical with that used by the U. S. Signal Service, distinguishes 10 grades, the names of which, with the cor responding pressures and velocities, are as follows: Velocity in Pressure in pounds

Grade.

1234567

English

miles and

avoirdupois on

Name.

per hour.

each square foot.

Very light breeze.

Gentle breeze.

Violent gale.
Hurricane.

Most violent hurricane.

Winds may be grouped in three classes-namely, constant, periodical, and variable winds; the first two are mainly tropical, the other characterizes the temperate and cold latitudes. To understand the cause of these differences and the general circulation of the winds we must inquire into their cause.

librium in the layers of the atmosphere, and the tendency Winds are the consequence of a disturbance of equiof their motion is to restore the equilibrium which has been destroyed; as soon as that is accomplished the movement ceases and everything settles into a calm. One of the chief conditions of this equilibrium of the atmosphere is, that any level layer should have the same density at all points; otherwise the denser portions flow under the less dense, while the lighter rise to the top. Now this occurs when the different parts of the layer are unequally heated. At the point of greater warmth the air expands, becomes lighter; then, pressed by the neighboring layers, which have remained colder and heavier, it rises into the higher layers, until it reaches a stratum of equal density with itself. The result of this process is an ascending current, and lateral currents rushing from all sides toward the spot where the temperature is higher. This is well exemplified in a heated stove. The warm and light air ascending in the pipe is replaced by a steady horizontal current of cold air rushing in from the surrounding atmosphere. effect, for moist air is lighter than dry air of the same temperature, and will cause an ascending current, or increase the ascending power of one already in progress. Moreover, when the moisture is condensed into rain, its latent heat, becoming free, adds to the buoyancy of the air.

Differences in the moisture of the air will have a similar

Land and Sea Breezes.-As an example from nature, let us see what takes place on an island alone in the midst of the ocean, remembering that the land is heated more readily than the sea. In proportion as the sun rises above the horizon, the island becomes warmer than the neighboring sea. Their respective atmospheres participate in these unequal temperatures; the fresh air of the sea rushes from all directions in the form of a sea breeze, which makes itself felt along the whole coast, and the warmer and lighter air of the island will ascend into the atmosphere. During the night it is the reverse. The island loses heat by radiation, and cools quicker than the sea. Its atmosphere, having become heavier, flows into that of the sea in the form of a land breeze; and this interchange lasts until the temperature, and consequently the density, of the two atmospheres have again become the same. This is the phenomenon observed almost daily on nearly all the seaboards.

The same again takes place on a great scale between an entire continent and the ocean, between the tropical regions and the temperate and polar regions. Southern Africa is fiercely heated by the rays of a summer sun, while the seas of India and Asia experience the low temperature of the winter. The temperature of the tropics is almost always the same, and constantly higher than that of the rest of the globe. To each of these differences of temperature, unequal in duration and amount, particular atmospheric currents, which are their consequence, correspond-to the difference of temperature between day and night, the diurnal breezes, whether along the coasts or in the interior of the continent at the foot of the mountains; to the difference of temperature between the extreme seasons, the monsoons,