Some data given by Wolff on mills of the American type gave for
the same quantity
W = 0.00045v3.
From some of the data of experiments by Griffiths on mills of the American type used in pumping, the effective work in pumping when the mill was working in the best conditions amounted to from 0.0005v3 to 0.0003v3 ft. ℔ per sec. per sq. ft.
In 1903 trials of wind-pumping engines were carried out at Park Royal by the Royal Agricultural Society (Journ. Roy. Agric. Soc. lxiv. 174). The mills were run for two months altogether, pumping against a head of 200 ft. The final results on six of the best mills are given in Table II.
A valuable paper by J. A. Griffiths (Proc. Inst. Civ. Eng. cxix. 321) contains details of a number of windmills of American type used for pumping and the results of a series of trials. Table III. contains an abstract of the results of his observations on six types of windmills used for pumping:—
TABLE III.
| I. | II. | III. | IV. | V. | VI. | |
| Diameter of wheel, feet | 22.3 | 11.5 | 16.0 | 14.2 | 10.2 | 9.8 |
| Sail area, square feet | 392.0 | 104.0 | 201.0 | 157.0 | 81.0 | 80.0 |
| Weather angle, outer ends | 18° 47′ | 43° | 36° | 30° | 28° | 50° |
| Weather” angle,” inner ends | 38° 20′ | 43° | 36° | 30° | 28° | 14° |
| Pitch of vanes, outer ends, feet | 23.8 | 33.7 | 36.5 | 25.7 | 17.0 | 22.4 |
| Pitch of” vanes,” inner ends, feet | 20.6 | 13.1 | 13.7 | 8.2 | 6.4 | 7.2 |
| Height of lift, feet | 25.000 100.000 | 29.200 61.2 | 39.0 | 66.3 | 38.7 | 30.7 |
| Velocity of wind at maximum efficiency, | ||||||
| miles per hour | 4.300 00 7.0 | 5.800 00 6.5 | 6.0 | 7.0 | 8.5 | 6.0 |
| Ratio of velocity of tips of vanes to velocity of wind | 00 .93 000 .77 | 00 .92 000 .82 | .65 | .91 | .87 | .73 |
| Revolutions of mill, per minute | 5.000 00 6.8 | 13.000 13.3 | 7.5 | 12.6 | 20.5 | 12.5 |
| Actual horse-power | 00 0.018 00 0.098 | 00 0.011 00 0.025 | 0.024 | 0.065 | 0.028 | 0.012 |
| In 100 average hours in a calm locality— | ||||||
| Quantity of water lifted, gallons per hour | 495.000 306.000 | 153.000 135.000 | 259.0 | 267.0 | 115.0 | 145.0 |
| In 100 average hours in a windy locality— | ||||||
| Quantity of water lifted, gallons per hour | 816.000 629.000 | 287.000 271.000 | 525.0 | 540.0 | 237.0 | 270.0 |
I. Toowoomba; conical sail wheel with reefing vane. II. Stover; solid sail wheel with rudder; hand control. III. Perkins; solid wheel, automatic rudder. IV. and V. Althouse; folding sail wheel, rudderless. VI. Carlyle; special type, automatic rudder.
Table IV. gives the horse-power which may be expected, according to Wolff, for an average of 8 hours per day for wheels of the American type.
| Diameter of Wheel in Feet. |
Velocity of Wind in Miles per Hour. |
Horse-power of Mill. |
Revolutions of Wheel per Minute. |
| 8½ 8½ | 16 | 0.04 | 70-75 |
| 10 | 16 | 0.12 | 60-65 |
| 12 | 16 | 0.21 | 55-60 |
| 14 | 16 | 0.28 | 50-55 |
| 16 | 16 | 0.41 | 45-50 |
| 18 | 16 | 0.61 | 40-45 |
| 20 | 16 | 0.78 | 35-40 |
| 25 | 16 | 1.34 | 30-35 |
Further information will be found in Rankine, The Steam Engine and other Prime Movers; Weisbach, The Mechanics of Engineering; and Wolff, The Windmill as a Prime Mover. (W. C. U.)
WINDOW (properly “wind eye”), the term applied in architecture (Ital. fenestra, Fr. fenêtre, Span. ventana, Ger. Fenster) to an aperture or opening in a wall for the admission of light and air to the interior of a hall or room.
The earliest windows are those which constituted the clerestory windows of the Great Hall of Columns at Karnak; they were filled with vertical slabs of masonry pierced with narrow slits. Other Egyptian temples were lighted in the same way. In one at Der el Medinet at Thebes the window was divided by miniature columns with lotus capitals. Some of the small ivory carvings found at Nimroud by Layard, now in the British Museum, are evidently of Egyptian workmanship, as they have lotus columns forming a balustrade in the lower part of the window; and such features are shown in the Assyrian bas-reliefs as windows in the towers. Dr Arthur Evans's discoveries at Cnossos have revealed, in the eastern portion of the palace, rectangular openings which were certainly windows, with raised sills and stone benches inside, and the representations of the ordinary houses of Cnossos on a series of plaques show that they were in two or three storeys with openings in the upper storeys filled with windows framed in timber with transoms and mullions. It was at one time thought that there were no windows in Greek temples, and those of the west front of the Erechtheum are known now to be later reconstructions of the Roman period, but the remains of two windows place on either side of the eastern doorway of the Erechtheum, which formed part of the original building of 430 B.C., have lately been found; they were rectangular windows with moulded and enriched architrave, resting on a sill and crowned with the cymatium moulding. Of later date, at Ephesus, remains of similar windows have been discovered. Of Roman windows many examples have been found, those of the Tabularium being the oldest known. A coin of Tiberius representing the temple of Concord shows features in the side wings which might be windows, but as statues are shown in them they are possibly only niches. Over the door of the Pantheon is an open bronze grating, which is thought to be the prototype of the windows which lighted the large halls of the Thermae, as it was absolutely necessary that these should be closed so as to retain the heat, the openings in the gratings being filled with glass. In some cases window openings were closed with thin slabs of marble, of which there are examples still existing in the churches of S. Martino and the Quattro Santi Incoronati at Rome. Similar slabs exist in the upper storey of the amphitheatre at Pola; it still remains, however, an open question as to the lighting of some of the temples at Rome, in which were placed all of the magnificent statutes from Greece so as to enable them to be seen properly. The Pantheon was lighted by a circular opening in the dome 30 ft. in diameter; the rain therefore fell in at times, and consequently the pavement had a convex contour, there being also holes under the hypaethral opening in connexion with drains beneath the pavement. There was a window at the south end of the tepidarium of the Forum baths at Pompeii, said to have been filled with a bronze frame with glass in it, half an inch thick. Although no window frames have been found in Pompeii, the openings in the walls show that some of the rooms were lighted by windows; one of them in the house of Diomede takes the form of a bow window with three lights in it.
In the later styles the windows assume much greater importance, and in Gothic cathedrals almost govern the whole design. Already, however, in the earliest Byzantine church, Sta Sophia at Constantinople, the windows constituted one of the chief features of the church; the forty windows round the base of the cupola giving an exceptional lightness to the structure; besides, there are windows in the larger and smaller apses and the north and south walls. The windows in the latter, which are of great size, are subdivided by marble mullions with pierced lattices between of transparent marbles.
In the later Byzantine churches the windows were of smaller dimensions, but always filled with marble screens, sometimes pierced, and the grouping of two or three under a single arch is the prevailing design.
In the Romanesque styles the windows are universally round-headed, with infinite variety of design in the mouldings and their enrichment, greater importance being sometimes given by having two or more rings of arches, the outer ones carried by small columns; this is varied in Norman work by dividing them with a shaft into two or more lights placed in shallow recesses under an arched head. Circular windows occur occasionally, as in the eastern transept of Canterbury, at Iffley church, Oxford, Barfreston and Patricksbourne in Kent. In all these early windows, which are usually small, greater light is obtained by splaying the jambs inside with a scoinson arch over them. The coupling together of two or more windows under a single arch, and the piercing of the tympanum above, led to the development of plate and rib tracery (see Tracery); also to that of the circular or rose windows, which throughout the Romanesque and Gothic periods constituted very important features in the church, being placed high up in the west front over the porch or in the transepts; sometimes, and more particularly in French churches, they occupied the whole of the upper portion of the windows, having vertical lights under them, but the junction was never quite satisfactory.
