54 



The Illustrated Book of Poultry. 



The chief merit of this incubator is the tank of cold water, which by its evaporation under the heat 

 above, percolates gradually through the chaff with which the egg-drawers are lined, and preserving 

 a moist atmosphere, renders any damping of the eggs unnecessary. The ventilation provided 

 through the pipe II is also of value. The principal defects which strike us arc, the absence of a 

 regulating-valve, and the immersion of the thermometer in the tank, or source of heat, instead 

 of being where it should be, in the drawer or chamber which is heated. The tank may preserve 

 the same temperature, and yet that of the egg-drawers differ widely, according as that of the room 

 rises or falls. Hence this incubator is more to be studied for the excellence of its general plan 

 than copied in its various parts ; and has never become extensively useful or jjopular, though 

 cheaply made. 



In 1866 Colonel Stuart Wortley, at that time an enthusiastic fancier, constructed an incubator 

 on another principle, which we think will yet be found valuable. A sketch .showing the 

 idea clearly was published in The Field from a drawing supplied by him, which we reproduce 

 in Fig. 30. D is a saddle-backed boiler, furnished with a dome, B, to collect all steam and allow it 



Fig. 30. 



to escape, a supply cistern, C, by which the height of the water is kept uniform, and a glass gauge, 

 A, to show the height at a glance. The water in the boiler is always kept boiling, and therefore 

 circulates at an almost uniform temperature through the pipes which heat 'the egg-chamber. 

 These pipes pass through holes furnished with spring-pads to keep them air-tight, and hence by 

 pushing in more length of pipes there is greater heat given given for cold weather, or by with- 

 drawing them a little the temperature may be reduced. The difference between this plan of 

 heating and others will be readily seen ; it gets rid of any variation so far as the lamp or other 

 source of heat is concerned, as the laws of nature give a uniform temperature of 212" for boiling 

 water at all ordinary pressures of the atmosphere. This is a great point, and changes of 

 temperature are then guarded against by giving more or less of heating surface. The difficulty 

 of providing a regulating-valve will readily be seen by all skilled mechanics, but we think luight 

 be overcome ; and in that case we believe all the mere mechanical difficulties of preserving a 

 uniform heat would be surmounted. We believe an incubator on this principle has never been 

 made for sale. We know one firm to have experimented with it, but the practical difficulties 

 we have hinted at have probably stood in the way of success, and the adaptation of a self-regulator 

 to this principle of heating yet remains for some ingenious inventor. We certainly think the field 

 a promising one, as the getting rid of lamp irregularities would be a very great point gained. 



Tlic most perfectly constructed incubator at present made for sale is probably that manufactured 

 by Messrs. Jacob Graves & Co., of Boston, U.S. It is evidently founded upon, and indeed is 



