Mr. Halsteds Regulator. 



59 



hole, D, through which the tube of tlic thermometer is inserted, the bowl being in the drawer. 

 There are only three points marked on the tube, 95°, 100°, and 105". The drawer is held tightly 

 in its place after being pushed under, by eccentrics, which force it upwards against the battens 

 that support the tank. 



Fig. 40 is the regulator. This is a glass tube, T, of about three-eighths or half an inch in 

 diameter and eight inches long ; at one end is a bowl holding half a pound of mercury. C is a brass 

 cylinder one inch long, fitting over the tube T, and slid down as near the bowl as is possible, where 

 it is secured by running a little plaster of Paris between it and the glass. To each side of this 

 cylinder is fastened a brass wire one-eighth of an inch in diameter, A A, which should be joined to 

 the cylinder as far back towards the bowl as possible, and forms a shaft on which the whole 

 arrangement balances or turns, the shaft of course turning with it. L is a lever on the long end of 

 the wire, and W a weight so connected that it may be moved along the arm of the lever. In making 

 tlie regulator, the bowl of the tube is partially filled with mercury or quicksilver, and then placed 

 in water heated to 100° Fahr. There must be enough mercury to fill the tube to the level showji in 

 the cut, at that temperature, when the tube has the inclination there shown. Then increase the 

 heat until the fluid rises and fills the tube, when the end is to be sealed hermetically. This should 

 be done by some manufacturer of thermometers. Then place the " regulator " under the tank and 

 near the centre of the drawer, supporting it by passing the wire A through journals or hangers. 

 A stay must then be put under the end of the tube T so that it can never quite descend to a 

 horizontal position. The end of the wire with the lever and weight is shown in the first 

 illustration (Fig. 35) projecting through the end of the case, and connected by the rod X to the 

 ventilating valves. To set the regulator, heat up the incubator to 103°, and then with the weight 

 \V balance the regulator. If the heat rises above that figure, the mercury rises in the tube, destro}-3 

 the equilibrium, the tube T descending turns the shaft A, and by the lever L opens the valves. 

 As the drawer cools the mercury recedes and the valves close. If desired the regulator can 

 also be connected with the lamp, increasing or decreasing the flame as the heat of the drawer 

 needs it. , 



The regulator of this machine, acting upon the balance system, is more delicate than the 

 preceding, and we believe has been found in practice to be more reliable. The absorption of the 

 water by the flannel in the egg-drawer between the strips V V is also a very valuable feature, 

 and comes nearer to an imitation of Nature's process than anything previous which has been 

 devised, while the whole is so simple that with the aid of a glass-blower to seal the regulator it can 

 be constructed by any skilful mechanic. The arrangement of the chicken-nursery over the top of 

 the whole machine, as in Mr. Schroder's incubator, is also convenient and useful ; indeed, the water 

 underneath and the ventilating shafts (in ihis case also employed for regulating the temperature), 

 with the nursery over, show a great similarity as regards the main outlines of the two machines. 



Such are the best incubators lately constructed. We believe we have omitted none containing 

 any principle worthy of remark, and need scarcely say that the "cheap and simple" machines 

 advertised at a very low price, and consisting only of a hot-water tank and drawer under, are 

 practically worthless, unless the proprietor could remain constantly by the side of them to regulate 

 the temperature. Excepting in trifling details of construction, perhaps a more perfect apparatus 

 than the last can hardly be devised, unless, as we have said, a regulating valve can be combined 

 with Colonel S. Wortley's plan of using water in the pipes at a regular heat of 212°, which we 

 still think would be the best principle of all. There are however practical difiiculties in the way, 

 and either the Graves or the improved Halsted incubator, are quite perfect enough for all useful 

 purposes if properly used. But in the use of all incubators the difficulties begin, and success can 



