FACTS OBSERVED IN HATCHING. 137 



burn the dung of cows or camels, mixed with straw, 

 formed into cakes and dried. The doors which open 

 into the gallery serve for chimneys to let out the 

 smoke, which finally escapes through openings in 

 the arch of the gallery itself. The fire in the gut- 

 ters is only kept up, according to some, for an hour 

 in the morning and an hour at night, which they 

 call the dinner and supper of the chickens ; while 

 others say it is lighted four times a-day. The dif- 

 ference probably depends on the temperature of the 

 weather. When the smoke of the fires has sub- 

 sided, the openings into the gallery from the several 

 rooms are carefully stuffed with bundles of coarse 

 tow, by which the heat is more effectually confined 

 than it could be by a wooden door. 



Transverse section and elevation of an Egyptian Egg-oven. 



When the fires have been continued for an inde- 

 finite number of days, eight, ten, or twelve, according 

 to the weather, they are discontinued, the heat ac- 

 quired by the ovens being then sufficient to finish the 

 hatching, which requires in all twenty-one days, the 

 same time as when eggs are naturally hatched by a 

 hen. About the middle of this period a number 

 of the eggs in the lower are moved into the upper 

 rooms, in order to give the embryos greater facility 

 in making their exit from the shell, than they would 

 have if a number of eggs were piled up above them. 



N 3 



