74 



THE BOOK OF POULTRY. 



enable it to resist all bending strains. To the 

 ends of the steel are firmly riveted, on both the 

 upper and under sides, strips of aluminium, which 

 expands more than the steel when heated. The 

 aluminium is kept flat down to the steel for a 



Fig. 42. — Cyphers Thermostat. 



certain distance from the ends by sliding ties or 

 rivets, which allow it to slide along, but not to 

 rise ; thus the expansion is all thrown towards 

 the centre, where the aluminium is not tied, and 

 rises into a bow. The action, therefore, consists 

 of four of these bows expanding with the heat, 

 and the superiority of this thermostat consists in 

 the strength and definiteness of the motion, and 

 rigidity of the whole, just as in the capsule 

 regulator. For the rest, the point of resistance 

 is the nut B at the end of the rod J, the upper- 

 most aluminium bow G lifts the tube C, sliding on 

 the rod j and through the casting A. The 

 motion is thus conveyed to knife-edges lifting 

 the lever H with its valve E, the lever also 

 working on knife-edges at I, and furnished at 

 the other end with an adjusting weight D. 



There is yet another point in regard to heat- 

 regulation. In some machines the egg-chamber 



is kept nearly uniform in tempera- 

 Double . ,, T1 • 1 1 . . 



Thermostats. ^^^^ ^'^ over. But m others, which 

 have a colder bottom, with the 

 heat radiated from the top, the temperature 

 differs greatly at various distances from the 

 radiator, and hence must be higher above the 

 fggs, in proportion as it is colder below them or 

 in the outer air, to keep the egg itself at the 

 same temperature. By many experiments, Mr. 

 Hearson found that with his machine, the heat 

 shown by the thermometer needed to be increased 

 one degree for about every ten degrees fall of 

 outer temperature; and this he directs to be regu- 

 lated for by the sliding weight. Every machine 

 of the top-heat type would have its own scale. 



It is possible to provide for this automati- 

 cally, though we only know at present of two 



actual attempts in this direction. The " Prairie 

 State " incubator is now made with a Z3-shaped 

 thermostatic bar, one limb of the :3 placed 

 above and the other under the eggs, and so 

 combined in their operation as to give a higher 

 temperature above the eggs 

 when it is colder below. The 

 result, we believe, is very satis- 

 factory. The other example is 

 English, in the regulator of 

 the " Forester " machine. This 

 is an ether-vapour regulator ; 

 but instead of a flat capsule, it is constructed like 

 a small funnel (Fig. 43), closed at both the 

 wide and small ends. The wide end is outside 

 the machine, in the open air ; and it will be 

 seen that, if the regulator were set for cold 

 weather, a considerable rise in outer tempera- 

 ture would appreciably diminish the heat 

 within the chamber which was required to 

 vaporise the fluid. 



We must now pass to a consideration of the 

 " hot-air " incubator, and here, as with the 

 " tank " machine, for purposes of 

 brevity we may well let one 

 standard type suffice. It is 

 American, and has achieved deserved popu- 

 larity, and claims, with undoubted success, to 

 entirely dispense zvitli moisture in hatching, in 

 any situation or climate. It is due to long 

 scientific investigation of all the phenomena of 

 hatching by Mr. Charles A. Cyphers, and the 

 master-patent under which it is made (December 



Hot-air 

 Incubators. 



Fig. 43. — "Forester" Regulator. 



4, 1894) is shown in Fig. 44. Here A A are the 

 walls of an egg-chamber B, and these walls are 

 all composed of a good thickness of porous 

 material. Mr. Cyphers has successfully used 

 wool or cotton compressed between sheets of 

 wire gauze, and slabs of plaster of Paris, but 

 prefers a manufactured material known in the 

 United States as " fibre stock," composed of 

 vegetablefibre, ground, pressed and dried, which 

 makes up readily into suitable walls. In the 

 diagram the whole surrounding walls are shown 



