The breasts/thee/a are those in which the water strikes the wheel on the upside, at a point intermediate between the vertical and the hori zontal lines passing through its centre ; and they aro made with buckets of analogous forms to those of overshot-wheels, in order to retain the load on the side receiving the water as long as possible, and having the same provisions for relieving the air, and for obviating the effects of the centrifugal force of the water. In small wheels the water strikes the buckets at an angle of about 40° from the vertical line ; in large ones the angle may be 30°, although some constructors make it as much as 52' for wheels of 20 or 30 feet in diameter. Evidently, however, the efficiency of a breast-wheel must depend upon the length of time it can retain the water on the loaded side, and the higher the point of impact, the greater must be the effect ; in other words, a wheel receiving the water only a little above the centre line, the loaded arc becomes en small as to produce very trifling results. If then the fall should not exceed 8 feet, it would be preferable to adopt an undershot-wheel working in a close race, rather than a breast-wheel; because it would allow the application of a larger first-motion wheel. With a good fall, and with well proportioned buckets, the useful effect of the breast-wheel is often as high as 010 PII.
In some parts of southern Europe, where °killed labour is not easily obtained, and the work required to be performed is of a very simple nature, a number of water-mills exist in which the wheel, instead of being placed vertically, is placed horizontally, and the mill-stones for corn or oil grinding are keyed at once upon the vertical shaft of the mill. Some of these machines have a series of
blades so placed upon the shaft, and with respect to the veiu of water striking them, (and it is generally the case that the water is conducted for this purpose in a pipe,) that the shock takes effect normally to the plane of the blades. The corn-mills of the Saracens were made in this manner, and the peasants of Galicia retain them to the present (lay; but the efficiency of these rude machines depends entirely upon the height of the fall disposable, and the useful result obtained is rarely as much as 0-15 en ; so that these mills are never seen in highly civilised districts. On the banks of the Garonne, Tarne, Lot, &c., numerous mills, such as those represented ink/. 6, are to be seen.
young oe cad plants, bi pots or in the open ground, the watering of the plant is always recommended.
In watering plants several inetrumenta are made use of, as the engine, the syringe, and the watering-pot. These are made either to threw water through tubes of various sizes so as to apply the water to a particular point, or Ly means of a rose which is appended to the tube to distribute the water over a larger surface. The former method is adopted when the roots of a plant aro to be watered, and the latter when it is wished to wet hole em-face. Where a stream can be made use of, an effectual way of watering plants is to have a sluice by which the water of the stream may be let on and off as may be thought proper. Tide is the best male of watering wnter.creases and other plants requiring abundant moieture. Where there are water-works, pipes are sometimes laid for supplying compartments of a garden. Lawns and plots of grass may bo watered from the water-butt.