a constant head when the wheel is in operation by carrying off what little surplus water the race delivers from the pond. [Illustration: Detail of bulkhead gate] At some point in the race or flume, the flow should be protected from leaves and other trash by means of a rack. This rack is best made of 1/4 or 1/2-inch battens from 1-1/2 to 3 inches in width, bolted together on their flat faces and separated a distance equal to the thickness of the battens by means of iron washers. This rack will accumulate leaves and trash, varying with the time of year and should be kept clean, so as not to cut down the supply of water needed by the wheel. The penstock, or pipe conveying water from the flume to the wheel, should be constructed of liberal size, and substantially, of two-inch chestnut planking, with joints caulked with oakum, and the whole well bound together to resist the pressure of the water. Means should be provided near the bottom for an opening through which to remove any obstructions that may by accident pass by the rack. Many wheels have plates provided in their cases for this purpose. The tailrace should be provided with enough fall to carry the escaping water back to the main stream, without backing up on the wheel itself and thus cutting down the head. It is impossible to make any estimates of the cost of such a water-power plant. The labor required will in most instances be supplied by the farmer himself, his sons, and his help, during times when farm operations are slack. _Water Rights of the Farmer_ The farmer owns the bed of every stream not navigable, lying within the boundary lines of the farm; and his right to divert and make use of the water of such streams is determined in most states by common law. In the dry-land states where water is scarce and is valuable for irrigation, a special set of statutes has sprung up with the development of irrigation in this country. A stream on the farm is either public or private; its being navigable or "floatable" (suitable for floating logs) determining which. Water rights are termed in law "riparian" rights, and land is riparian only when water flows over it or along its borders. Green (Law for the American Farmer) says: