52 
The Illustrated Book of Poultry . 
traveller in Egypt who has noticed the subject in any way, that the professional hatchers can 
detect at a glance all fertile eggs provided they are fresh. To us this fact may seem almost in- 
credible ; but with the multiplied testimony to it, it would be most foolish and rash to pro- 
nounce it so, simply because we have at present no means by which we can pronounce such a 
decision ourselves. If it be a fact, then the long practice of the profession has given these 
children of nature a knowledge which may well have guided them to success in other 
particulars. 
From the very commencement of attempts in this direction there has been success sufficient 
to show that the thing coidd be done, and that the “how” was only a question of details. An 
“ Eccaleobion ” constructed in 1777 by M. Bonnemain was really to some extent used in a 
commercial way, and many chickens hatched in it were actually sold in the Paris market. Reaumur 
also obtained very fair results by surrounding wine-casks, in which the eggs were placed, with 
fermenting dung, renewed as often as the heat decreased. Cantelo appears to have been the first 
to consider that the heat should be applied from above, in imitation of the hen. We remarked in 
our last chapter that in the early stages of incubation, in whatever position the egg be placed, the 
yolk floats with the germ uppermost, and this is probably to bring it more under the influence of 
the warmth from the hen’s breast ; though the fact that both Chinese and Egyptians hatch in large 
apartments, where the air surrounding the egg is all of one temperature, proves that this arrange- 
ment can hardly be of the importance some have supposed. Be this as it may, Cantelo’s apparatus 
hatched a very fair number of chickens, but was too expensive ever to come into general use , and 
the same may be said of the elaborate incubator of M. Minasi, which it is unnecessary to describe. 
We shall confine our attention, as regards the earlier machines, to those which contained either 
some novelty, or some feature afterwards proved to be of real importance. 
For one of the most essential points of a good incubator, poultry-keepers are indebted to M. 
Vallee, Poultry Superintendent of the Paris Jardin des Plantes. About the year 1845 this gentleman 
constructed an incubator which succeeded very fairly, hatching considerable numbers, not only 
of hens’ eggs, but those of partridges, pheasants, and even reptiles. M. Vallee finally improved 
his machine by the addition of a self-acting valve, by which the temperature was to a certain 
extent self-regulated. This valve was by no means perfect in its action ; but the idea was most 
valuable, and has been adopted in all the best incubators of the present day. 
An incubator which contained several points still found essential was invented by Mr. F. 
Schroder, manager of the now defunct National Poultry Company, and which is illustrated in 
Fig. 29. It was circular in plan, and very compact. The hot-water tank, c, was connected with 
a separate boiler, not shown in the figure, by two pipes, B and D, one being the inlet pipe and 
the other the outlet ; and was furnished with an open pipe, I, in which is immersed a thermometer 
to show the temperature. Under the tank slid the egg-drawers E E, each of them the quadrant 
of a circle, all being open at the top, and the bottoms being formed of perforated zinc. A tube. H, 
which passed through the tank, afforded ventilation to all the drawers, the corners of which met 
under it. Under all again was a circular tank, F, of cold water; and over the hot-water tank was 
a circular receptacle bounded by perforated zinc all round the apparatus, and floored with sand, 
both to confine the heat and furnish a home for the chickens till strong enough for removal. 
Curtains were provided all round to preserve the heat, and guard in some measure against changes 
of temperature. The chief merits of this incubator were the ventilation, and the tank of cold 
water, which, by its evaporation under the heat above, percolated gradually through the chaff 
with which the egg-drawers were lined, and, preserving a moist atmosphere, rendered any damping 
of the eggs unnecessary. The principal defects were, the absence of a regulating-valve, and the 
