Ventilation and Moisture Next
Ventilation and the retention of moisture undoubtedly come next. The growing embryo must be fed a large quantity of oxygen, and there must be a sufficient amount of moisture to prevent a too rapid drying out of the egg, under the temperature which, if a chick is to result, must be maintained. So far as moisture goes, it is not a question of moisture at the time of hatching. If the proper amount of moisture has been always present during the period of incubation there will be no difficulty at the time of exclusion.
Where a large amount of incubation is going on, and the ordinary style of lamp heated machine is being used, oxygen is of necessity constantly absorbed from the atmosphere, by the fire. While it is quite possible, nay, even probable, that any of the mammoth machines of the day are far from what might be desired, still, they do solve the difficulty of a great number of individual fires sucking the vital oxygen.
Of the mammoth machines now on the market there are two which produce better chicks than any of the others, so far as we can see. There are features in the one which we finally decided upon, which, from our point of view, made it more desirable than the other. We feel, however, that in the construction of these machines there is much to be desired, and we suggest to any would-be purchasers to make most thorough and complete stipulations with any company from whom they purchase, as to the workmanship and finish of the machine, and also the proper fitting of one part to another, especially the proper working of doors and egg trays through all the different periods of incubation. All trays should be absolutely interchangeable, and there should be a sufficient amount of play in the runs, so that, with the swelling of the wood from the moisture, there would never be a possibility of their binding. While the doors should shut air-tight, their dove-tailed joints should so fit as to allow their coming away without a particle of stick, or jar, to the machine.