The two kinds of wheels, center-vent and circumferential vent, are commonly called " turbines." The water passes through the buckets of the former from the outside to the inside ; through the latter from the inside, discharging at the circumference. In this respect they differ entirely from the overshot, breast, and undershot wheels, which have closed buckets, and discharge their water by the same mouths at which it enters. Turbine wheels are now very generally employed in our country and France, and their use is rapidly extending. They are nearly as old as the overshot wheel ; but they were seldom used prior to 1830, as until about that period they were held in very low esteem. By various valuable improvements, however, made of late years, they have assumed an important place as prime hydraulic motors, and in many cases have superseded all other kinds. They occupy less space, their first cost is much less, (especially for high falls) than overshot and other wheels, and when properly constructed, they give out as much of the power of the water. For these reasons they are preferred for many situations. The accompanying engravings represent the turbine wheel of Reuben Daniels, of Woodstock, Vt., to whom was issued a patent for his improvement June 2, 1857. Fig. 1 is a perspective view of the wheel, with its adjunctive machinery ; Fig. 2 is a sectional plan view of the buckets, with the top flanch removed ; and Fig. 3 is a vertical section of the mouth of the flume and the gate, for regulating the supply of water to the wheel, andfor shutting it off and letting it on. The common turbine is enclosed in a tight draft box or scroll, filled with the water, which is admitted to all the buckets simultaneously. The wheel here represented has no draft box enclosing it ; it is open to the air, and the water is admitted at the center of the flume, F; and instead of operating on the buckets simultaneously, it acts upon them in succession as they rotate. A is the framing of the wheel, M ; B are the bearings. The shaft, N, has a bevel gear, 0, on its upper end, meshing into another, D, on the shaft of the iTand pulley, E, which drives the connected machinery. In Fig. 3, G represents the mouth of the water flume, on which there is a horizontal sliding gate, H, having a rack on its back, into which matches the pinion, I, on the foot of the rod or spindle, J. By turning the handle, K, of this rod, the sliding gate, H, is slid back and forth to regulate the size of the mouth or opening, G, to increase or diminish it, according to the quantity of water to be admitted to the buckets, L. The upper flanch, F', of the wheel projects beyond the lower plate a distance equal to the width of the orifice, through which the water flows to act upon the buckets. By this broad flanch, and the sliding gate, H, the water is so controlled and guided into the wheel that it acts directly upon the buckets until it escapes at the circumference. Common turbines (both centervent and outer vent) have narrow top flanches, about the same width as the buckets ; therefore, by the centrifugal action generated as the wheel rotates, the water tends to rise over the buckets, and is dragged round, thereby causing a considerable resistance, which is sometimes very disproportionate to the quantity of water admitted, thus absorbing much of the power. This evil is designed to be obviated by the arrangements in this wheel. As the center of this wheel is open to the air, and as the centrifugal action causes a partial vacuum to be formed at the center, the air rushing in forms a negative back to the water, and allows it to discharge freely. In enclosed center inlet wheels, the water must be fed in to keep them full, and supply the vacuum ; and a center-vent wheel must also have its scroll or flume kept full of water. For varying quantities of water, which is common to all streams during the different seasons, changeable buckets in wheels have been resorted to for meeting this difficulty, but they are of troublesome and complex construction. This wheel, therefore, will operate according to the quantity of the supply water, be it much or little, and during periods when the quantity of water may be too small to drive the-class of wheels referred to. For more information address Mr. Daniels, as above.