VIII. On the physics of incubation

It is generally agreed that a considerable discrepancy still exists between the results of natural and artificial incubation; a larger percentage of eggs hatching out, on the average, under hens sitting in properly designed nests than in the best incubators. Exactly what this discrepancy may be is not certainly known - figures obtained a few years ago by the Board of Agriculture point to about 20 per cent.-but that it is worth taking into account in hatching on a large scale there is little doubt. Whether, if the physical conditions obtaining under the best sitting hens were known and could be exactly reproduced in incubators, incubators would hatch eggs as successfully as hens may be open to question; but it is reasonable to suppose that the quality of a hatch is at any rate very largely determined by these conditions, and their study is thus likely to lead to improvement in artificial hatching.