RANKIN'S DUCK BOOK 



all depends upon its accuracy. Do not use one with the mer- 

 cury bulb lying upon a solid metal plate, as the refraction of 

 heat upon the plate from the tank above will always run that 

 glass one or two degrees higher than the heat in the egg- 

 chamber, but get one, if possible, with a hole in the plate oppo- 

 site the bulb, so that the heat can play around the bulb and 

 through the plate, giving the correct heat of eggs and chamber. 

 Do not hang your glass up over the eggs, or put it down 

 between the eggs, but lay it on them, for the reason that, 

 though either of these positions may be all right during the 

 first twelve days of the hatch (if your eggs are fertile), they 

 will surely be all wrong during the last part. 



I will endeavor to explain this thing, so that the novice 

 will understand how important it is. Before circulation begins 

 in the embryo chick or duck, and there is no animal heat in 

 the- egg, the temperature -of the egg .chamber -regulates that 

 of the eggs. But after circulation begins, and especially during 

 the latter part of the hatch, when the rapidly-developing young 

 bird throws out a great deal of heat, the thing is often com- 

 pletely reversed. For instance, a glass may be hung one inch 

 above the eggs and another placed immediately on the eggs 

 beneath. The one above may register 102 degrees; the one 

 below, on the eggs, will register 105 degrees, — conclusively 

 showing that the eggs are now, by their own caloric, heating 

 the egg-chamber. 



I have often, during the last part of a hatch, when the 

 thermometer was ranging from 70 to 80 degrees outside of 

 machine, placed a glass on the hottest part of the boiler, where 

 but one lamp was dimly burning, carefully covering the glass. 

 In that position it would register perhaps 96 to 98 degrees, 

 while a glass inside the machine, and on the eggs, would reg- 

 ister 103 degrees, proving beyond a doubt that the eggs, by 

 their own caloric, were not only heating the egg-chamber, but 

 contributing their quota towards heating the water in the 

 tank. Now, who will pretend to say that a glass hanging 

 above the eggs will give the correct heat of the egg after cir- 

 culation begins. So that, even in cold weather, the amount 

 of oil consumed during the last week of the hatch is less 

 than half the amount required during the first part. 



The operator must not expect the eggs to heat up at 

 once. On the contrary, they will cool the air in the egg- 

 chamber very sensibly, though they will not affect the heat 

 of the water in the tank. It will be from five to eight hours 

 before they arrive at their normal heat. 



t 48 J 



