tube; and when water has been admitted into the other, it is boiled over a lamp till all the air is expelled; and while the stream is still issuing with violence through the capillary extremity, the end of it is held in the flame of the lamp, till in proportion as the force of the steam diminishes, the heat acquires power to seal the tube hermetically.
When such an instrument has been successfully exhausted, if the empty ball he placed in a freezing mixture of salt and snow, the water contained in the opposite ball will be frozen solid in a very few minutes.
The first vapour being condensed by the common effect of cold, is immediately succeeded by a fresh emission, with proportional reduction of temperature; so that heat is continually withdrawn, or cold generated at a distance by the freezing cause.
In the first of these birds the solvent glands are different from those of any other bird examined by the author, each gland being made up of five or six cells, that open into one common excretory duct; but its gizzard is very similar to that of the crow.
In the Emu the solvent glands are oval bags, one fourth of an inch in length, and one sixteenth wide. The gizzard differs from that of the crow in having a thicker lining, and is remarkable solely for its situation; for it is not placed, as usual, between the stomach and the duodenum, but forms a pouch on one side, so that food can pass onwards direct into the duodenum, without being received into the gizzard.
In the Cassowary of New South Wales, the solvent glands are similar to those of the emu, but larger; and the gizzard is also similar in every respect, but stronger.
The author further remarks upon the circumstances in the structure of the cassowaries, and other birds most nearly allied to them, which adapt them to the different degrees of fertility of the countries they inhabit.
The Emu of Java, where there is abundance of food, has intestines that are of large diameter, and comparatively short, so as to afford free passage to the superfluity of food they take. and a gizzard to be employed only occasionally.
The Cassowary of New South Wales has intestines of smaller diameter, thirteen feet long; and a stronger gizzard, more frequently employed in a less productive country.
