distant from the bottom, and the highest a few inches lower than the upper edge. When the time had elapsed in which my previous experiments had failed, not one egg in this new oven was tainted, and at the end of twenty days the gardener, who had taken care of so many unsuccessful broods, came in the evening to tell me, with the greatest possible emotion, what he knew must be very pleasing news, namely, that one of my eggs was chipped, and the chick could be heard within endeavouring to chirp. This chicken did not disappoint our hopes, having been hatched next day, and it was even preceded by some others, and followed by a great many more. From that time, indeed, I began to see some hatched every day*."

The problem with respect to heat generated by fermentation was thus solved; but M. Réaumur did not stop here. The rector of St. Sulpice, anxious to introduce the plan, applied to the naturalist for instructions on the subject; but, instead of recommending dung-beds, M. Réaumur imagined he might *L'Art de faire Ecclorre, Mem. ii,

take advantage of the heat of the bread-ovens belonging to the extensive benevolent institution called L'Enfant Jésus. After several trials to ascertain the heat of a room which was situated over this bake-house, and such arrangements as were necessary to insure uniformity, it was determined to arrange the eggs on the shelves of a small cupboard placed there, and the care of them was entrusted to the nuns of the establishment. In one of the first experiments made here, the charge of keeping a single box, containing a hundred eggs, was entrusted to a very ingenious nun, who was really enthusiastic in the business. Above half of these eggs proved abortive; but it was worthy of remark, that about twenty were hatched one day sooner than they would have been under a hen. When the first of them appeared the nun was transported with joy, and directly ran to tell the news to every body she could find.

It was an obvious inference from the success of these experiments, that bakers and pastry-cooks might apply their ovens to a similar use by constructing over them hatching chambers, and that in this way the multiplication of chickens might be extended to an immense amount-far exceeding even that of Egypt. It does not appear, however, that these notions have ever been carried into effect, or that anything has been attempted beyond a few experiments of small extent, in any part of Europe. A few years ago an individual in the vicinity of London contrived an apparatus for hatching by means of steam, and exhibited it in the Egyptian Hall, Piccadilly; but we have not learned that he ever carried his invention so far as to make a trade of the chickens which he hatched.

The importance of keeping the eggs at a uniform temperature is beautifully illustrated by the care which hens may be observed to take in arranging the eggs they are hatching. Amongst other curious facts connected with this subject, is that of a hen throwing out or eating the eggs which she cannot conveniently

cover.

A few days ago we had brought to us three eggs of the wood-wren (Sylvia sibilatrix, BECHSTEIN), and being anxious to have them hatched we introduced them, after warming them slightly, into the nest of a canary, then sitting upon four eggs of her own. In the course of the day two of her own eggs had disappeared, having, we inferred, been destroyed by her because she could not cover the seven so as to keep them at a uniform temperature, the three small eggs being nearly equal in size to the two which were gone*. It is, no doubt, for the same

* J. R.

reason that the birds, in whose nests the cuckoo parasitically deposits her egg, often, if not always, turn out or destroy their own to make room for hers.

During the process of hatching the mother-bird acts as if she knew that by keeping the eggs all in one position, some would be more favourably treated than others.

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CHAPTER IX.

EVOLUTION OF THE CHICK.

IT has long been a favourite occupation with philosophical naturalists, to observe the changes which an egg undergoes in hatching, from the first day that the mother sits upon it till the chick breaks through the prison-walls of the shell and emerges into open day. The chief writers who have attended to the various stages of this curious and interesting progress, are Fabricius d'Aquapendente, Harvey, Malpighi, Maitre-Jean, Réaumur, Haller, Scarpa, Meckel, Blumenbach, Prout, Dutrochet, and Sir E. Home. The statements of these different inquirers we shall now compare and condense.

An Egg as it appears twelve hours after incubation, with a magnified view of the Embryo Chick.

"(This and the following cuts, which illustrate the changes in the egg," are copied, by permission, from Sir E. Home's Comparative Anatomy.)