1939. Kewley's regulating thermometer, or automaton gardener (fig. 528.), consists of a particular application of the alarum-thermometer just described. For this purpose, the thermometer is made from two to three feet in length, and the same principle may be extended to any length, as ten or twelve feet, with a proportionate increase in the diameter. The apparatus which Kewley applies to the thermometer, and which enables him to get the power requisite for opening the sashes or windows of hothouses or buildings of any magnitude, is a metal cylinder (h), generally of rolled copper, as being cheapest, from seven to fourteen inches in diameter, and from eighteen inches to two feet in length. with an accurately fitted piston (i). This cylinder is placed either within or without the hothouse or room in any convenient situation, and a cistern, or a barrel of ordinary dimensions, filled with water, is placed on an elevated situation, say on a level with the chimney-tops. The deeper the cylinder is sunk, the less the cistern requires to be raised above the level of the floor of the house. If, as is often the case, a pipe of water is conducted through the house from a distant reservoir of ordinary elevation, then nothing more is necessary than attaching a branch-pipe. It is requisite that this pipe pass directly to the point where the thermometer is placed, and at any convenient distance under it, not higher than the bottom of the cylinder. Here it is joined to a tripartite cock (k), whence proceed two other pipes, one (l) to the cylinder, and the other (m) to a waste drain. The stopper to this cock turns only to the extent of about one fifth of a circle; and when turned to this extent to the right, it opens a communication between the supply-pipe (n) and the cylinder (h), when the pressure of the water in the reservoir, whether a barrel on the top of a house, or a distant cistern, raises the piston, and by a communication of cords and pulleys with the sashes (o) they will be raised or opened; and by another chain (p), the fire or steam damper (q) will be opened also. When the cock is turned to the left, this communication is stopped, and one opened between the cylinder and waste-pipe (m), by which the water escaping, the piston descends, and the sashes and dampers are shut. The equilibrium of the balance-thermometer restored by the temperature, being reduced or elevated to the proper degree, the plug is neither turned to the right nor left, and every communication is closed. The cock is worked by two wires (r r), fastened to two short levers, fixed on each side of the thermometer-frame, and the other ends of the cross or handle of the cock (s s). To set the machine at work, it is only necessary to place the scale to a degree at which it is desirable air should be given, taking care that the cistern is not without water. A small cask of water regularly supplied, will answer as well as a large cistern, as the power is not as the body of water, but as its height. Where light valves or ventilators are used, the balance-thermometer of this size has sufficient power to open them without the aid of machinery; and by lengthening the tube, sufficient power may be obtained to open balanced windows in dwelling-houses, churches, or hospitals.
