odor simply the mysterious agent which chem- 

 istry has named caloric. 



Suppose we fill the heat reservoir with water, 

 coffee, milk or wine, and heat the liquid say, to 

 150, what follows? Why the heat (caloric) 

 radiates from the metal bottom of the reservoir 

 and is diffused through the egg chamber, just as 

 it does when the reservoir contains air, and this 

 radiated caloric or heat mingles with the air in the 

 egg chamber and is absorbed by the eggs until 

 they and the air immediately surrounding them 

 are heated to 102, 103 or 104, according to the 

 desire of the operator. 



The air in the egg chamber thus becomes warm 

 air or "hot air," and if there is good ventilation 

 in the egg chamber, the hot air is not foul air. 



Now, what becomes of the assertion that "hot 

 air is necessarily foul air." 



When it comes to the question of hot water 

 heaters or hot air furnaces for heating houses, an 

 entirely different principle is involved. Although 

 you get no moisture at all from hot water pipes, 

 you get pure heat from them ; but the hot air fur- 

 nace is heated red hot or nearly so, and the current 

 of air which passes over this superheated surface 

 is burned, or loses a greater portion of its oxygen 

 before it enters the room mingled with the heat, 

 and it also has a chance to carry coal gas with 

 it. The hot air of the house furnace passes 

 directly from the furnace into the room. 



Not so with the hot air heater of the incubator, 

 for it will probably be heated to about 150 and 

 23 



\m J J> *b & C& el) fo els els els ejs <J> J3 Js <J* Is ti els ejs els 3s els ej ejj els ejs el els J els c& els els els ejs els els els els 3s to/ 



