INCUBATION, ARTIFICIAL 



m, to establish a draught in this circuitous chimney. The air is admitted into the 

 ashpit at tho side, in regulated quantities, through a small square door, moveable round 

 a rod which runs horizontally along its middle line. This swing valve is acted upon 

 by an expanding bar (see HKAT-REGTTLATOE), which opens it more or less, according 

 to the temperature of the stove apartment in which the eggs are placed. 



D is the upper orifice of the boiler, by which tho hotter and consequently lighter 

 particles of the water continually ascend, and are replaced by the cooled particles, 

 which enter the boiler near its bottom, as shown in Jig. 1209 at E. Into further details 

 relative to the boiler it is needless to enter ; for though its form, as designed by M. 

 Bonnemain, is excellent and most economical of heat for a charcoal-fire, it would not 

 suit one of pit-coal, on account of the obstruction to the pipes which would soon bo 

 caused by its soot. 



In fig. 1209 the boiler is shown at E, with the rod which regulates the air-door of the 

 ashpit. D is a stopcock for modifying the opening by which the hotter particles of 



1209 



water ascend ; G is the water-pipe of communication, having the heating pipe of dis- 

 tribution attached between E F, which thence passes backwards and forwards with a 

 very slight slope from the horizontal direction, till it reaches the poussiniere o P Q. It 

 traverses this apartment, and returns by N N to the orifice of the boiler H, where it 

 turns vertically downwards, and descends to nearly the bottom of the boiler, discharging 

 at that point the cooled and therefore denser particles of water to replace those which 

 continually issue upwards at D. L E is a tube surmounted with a funnel for keeping 

 the range of pipes always full of water; and K is a siphon orifice for permitting the 

 escape of the disengaged air, which would otherwise be apt to occupy partially the 

 pipes and obstruct the aqueous circulation. 



The faster the water gets cooled in the serpentine tubes, the quicker its circulation 

 will be, because the difference of density between the water at the top and bottom of 

 the boiler, which is the sole cause of its movement, will be greater. N represents 

 small saucers filled with water, to supply the requisite moisture to the heated air, and 

 to place the eggs, arranged along the trays M M, in an atmosphere analogous to that 

 under the body of the hen. 



When we wish to hatch eggs with this apparatus, the fire is to be kindled in the 

 boiler, and as soon as the temperature has risen to about 100 F., the eggs are intro- 

 duced ; but only one-twentieth of the whole number intended, upon the first day : next 

 day a like number is laid upon the trays, and thus in succession for twenty days, so 

 that upon the twenty-first day the eggs first placed may be hatched for the most part, 

 and we may obtain daily afterwards an equal number of chicks. In this way regu- 

 larity of care is established in the rearing of them. 



During the first days of incubation, natural as well as artificial, a small portion of 

 the water contained in the egg evaporates by the heat, through the shell, and is re- 

 placed by a like quantity of air, which is afterwards useful for the respiration of the 

 animal. If the warm atmosphere surrounding the eggs were very dry, such a portion 

 of the aqueous part of the eggs would evaporate through the pores of the shells as 

 would endanger the future life of the chick in ovo. The transpiration from the body 

 of the hen, as she sits upon her eggs, counteracts this desiccation in general ; yet in 

 very dry weather many hatching eggs fail from that cause, unless they be placed in 

 moist decomposing straw. The water-saucers N N are therefore essential to success in 

 artificial incubation. 



After the chickens are hatched, they are transferred into the nursery, o Q, on the 

 front side of which there is a small grated trough filled with millet seed. Small 

 divisions are made between the broods of successive days, to enable the superintendent 

 to vary their feeding with their age. 



