EGGS. The eggs of bens and of birds, in general, are composed of several dis tinct substances. 1. The shell or exter nal coating, which is composed of car bonate of lime .72, phosphate of lime :2, gelatine .3 ; the remaining 23 are, per haps, water. 2. A thin, white, and strong membrane, possessing the usual charac ters of animal substances. 3. The white of the egg, for which see ALBUMEN. 4. The yolk, which appears to consist of an oil of the nature of fat oils, united with a portion of serous matter sufficient to ren der it diffusible in cold water, in the form of an emulsion, and concrescible by heat. Yolk of egg is used as the medium for rendering resins and oils diffusible in wa ter. An oil of eggs is procured by ex pression from the yolks of eggs, previous ly roasted; to deprive the serous part of its fluidity. A slight empyreuma is given to the oil by this treatment, which might probably be avoided by applying no great er heat than, on trial, might be found suf ficient to coagulate the serum.
The products afforded by the several parts of eggs subjected to destructive dis tillation are nearly the same as are ob tained by that method from other animal matters.
Mr. Reaumur found that eggs might be preserved during months or years by be ing covered with mutton-suet, or any other fat substance. And Mr. Parmentier observed that eggs of hens that have had no connectii.n with a cock kept much better than those which are fecundated : he adds too, that they are not inferior in size or flavour, and that the hens lay quite as many: so' that those who keep fowls for the sake of eggs alone should have hens only, without any cocks. He re commends the common hen as the most productive, and the black legged as su perior to the yellow.