The modern Chinese are well acquainted with the me thod of hatching chickens by artificial heat. Mr Barrow mentions, that even those families practise it who have a permanent abode on water. They deposit the eggs in sand, at the bottom of wooden boxes, which are placed on iron plates kept moderately warm. Thus, while a new brood is obtained, the old birds continue laying nearly without interruption.
M. de Reaumur, an ingenious naturalist, devoted much time and attention to the subject of hatching eggs by artifi cial heat, whieb he seems to have been desirousof introduc ing into France under the superintendence of a Bermean. He adopted methods of accomplishing this, which are copiously detailed in a work on the subject, that has been translated into several European languages. Two plans were principally fcatowed; the first, which was analo gous to that of the Egyptiam..consisted in raising a super structure above three bakers for containing the eggs. A small carriage on wheels, or rollers, was formed, in which were several drawers, or shelve,-, whereon the eggs were placed in successive rows, or strata, •.hat is, one layer on each. The carriage could be brought pleasure on its wheels to any part of the surface, and the sate of all the eggs could be ascertained on pulling out the s'Aelves, or drawers, in which a thermometer likewise lay, for 'Atli eating the heat. By means of this simple apparatus, Reau mur succeeded perfectly in hatching chickens ; and he ac quaints us, that a nun, to whom he entrusted his first ex periment, in the oven of a convent, obtained 20 from 100 eggs. He conceives that a suitable oven, twelve feet square and four feet high, with a stove in the centre, could be erected at little expellee, which would necessarily he heat ed to 104°. Instead of thermometers, the temperature may he ascertained by melting a piece of butter, as large as a walnut, with half as much tallow in a phial. When it flows like a thick syrup on inclining the phial the proper heat is obtained.
The second, though a less efficacious plan, adopted by Reaumur, consisted in burying casks of eggs in a dunghill, the warmth of which might promote exclusion. Here, however, he was opposed by uncommon difficulties; and he acknowledges that, had the former expedient been first de vised, he should never have resorted to the latter. His ex
periments were originally made by depositing the eggs simply in the dunghill in an oblong cavity, covered by two planks. Most of them advanced favourably during eight or ten days; but after this they became putrid, disseminating an infectious effluvia, and not one produced its young. On employing casks, Reaumur suspended three flat baskets or sieves at intervals within them, containing one or two layers of eggs, along with thermometers. However, the tem perature of the dunghill being subject to continual varia tion, occasioned great embarrassment ; and the author con ceives that the experiment may be more successful by re sorting to several, which may possess different degrees of heat. To preserve it permanently equal is very difficult ; and turning the eggs is also attended with trouble. In the course of his experiments, Reaumur found, that, though the temperature should be regularly 104°, the expanding embryo could exist at from 1 to 122° ; and that an egg, during the period of total developement, loses about a fifth or sixth of its weight. He found that a humid and mephitic vapour arising from the dunghill injured the nascent young more than heat. He therefore devised a new kind of oven, heated in the same manner as the casks by a dunghill, but resembling the stiperstructure he had used on the baker's oven. This was a rectangular box or case, six or seven feet long, between 21 and 40 inches broad, and about 8 inches high. It was immersed in a dunghill, leaving one end open, and the eggs were placed on a carriage or tablet moved in upon rollers. By observing proper precautions, Reaumur succeeded in hatching about three-fourths of the eggs he employed.
From the brief abstract now given, a general idea may be formed of the two different methods ; but M. de Reau 'nut's work itself must be consulted for the details. As it is not uncommon, we shall proceed to give an account of other expedients suggested or adopted by a more recent naturalist, the author of the Ornithutrophie Artificielle ; more especially as we do not know that they have ever been alluded to in any English work.