water conveyed direct into the river Eagley, at B. When replacing this wheel by a new one, it was found that by taking advantage of a bend in the river, and conveying the tail-water to c, an increase of about 6 feet of fall could be obtained. Hence a wheel 32 feet in diameter was adopted, with a fall of 28 feet; and for the tail-race a tunnel D D was constructed, nearly a quarter of a mile long, and passing under the bed of the river at B, so as to meet the stream on the other side of the field at c. The substratum being composed of hard rock and shale, afforded every facility for the drifting of the tunnel, and when complete, the flow of water through it was so exceedingly sensitive, that only a few gallons falling from the wheel into the trumpet mouth at A, immediately caused a perceptible discharge into the river at c, at a distance already stated, of nearly a quarter of a mile. The perfect success of this arrangement caused its adoption in other cases, where the conditions were favourable for carrying it out.

The Catrine High-breast Wheels.-Plates I. and II. illustrate the construction of the improved iron high-breast wheel as applied at the Catrine Works in Ayrshire, between the years 1825 and 1827, on a fall of forty-eight feet. Taking into consideration the height of the fall, these wheels, both as regards their power and the solidity of their construction, are even at the present day among the best and most effective structures of the kind in existence. They have now been at work upwards of thirty years, during which time they have required little or no repairs, and they remain nearly as perfect as when they were erected.

It was originally intended to erect four of these wheels at the Catrine Works, but only two have been constructed. Preparations were made, however, for receiving two others in the event of an enlargement of the reservoirs in the hill districts, and more power being required for the mills. This extension has not as yet been wanted, as these two wheels are working to 240 horses' power, and are sufficiently powerful, except in very dry seasons, when they are assisted by auxiliary steam-power, to turn the whole of the mills.

Plate I. is a plan of the wheel-house, showing the position of the wheels, and the arrangement of the main gearing. The

first pair of wheels is shown in section, to exhibit the main axle, arms, braces, spur segments, and pinions. The other pair are shown in plan, one exhibiting the buckets, and five rows or bucket-stays, while the pentrough, sluice, and regulating gear are shown on the other. It will be seen that the motion of each pair of wheels is transmitted through a common pinion shaft, and thence by another pinion and spur-wheel, by which the velocity is increased to the first motion shaft of one mill, whilst between the two pairs of wheels there is the first motion shaft of another mill geared into the preceding shaft by a pair of large bevel wheels.

Plate II. is an elevation of the wheel-house, with the masonry for supporting the wheels, tail-race, tunnel, &c. The right half of the wheel is shown in section, and the left half in elevation, and there is a section of the pentrough, sluice, and plates, to guide the water into the buckets.

The following are the references to the different parts of the wheel:

c, tunnel running through the wheel-house, and acting as the

tail-race.

D, pinion gearing into internal segmental spur-wheel on shrouds.

E, wheel on the same axis as D, and communicating the power

to the pinion F on the first motion shaft.

G, galleries to obtain access to the pentrough and other parts of the wheel.

The water is brought from the reservoirs in a tunnel 10 feet in diameter, through the hill part, and thence in a conduit 12 feet wide, and 5 feet deep, arched over. The reservoirs cover 120 Scotch acres, of an average depth of 8 or 10 feet, giving storeage room for a large supply of water; and the sill of the reservoir sluice, from which the aqueduct bottom is carried