188 . EGGS 



edge. He piled a slab or plate of steel upon two or more similar plates of iron ; heated 

 it in a furnace to a good welding heat, and then passed it between grooved or other 

 suitable rollers to convert it into bars ; the steel being in a thin layer either on one 

 of the outer surfaces of the bar, or between two surfaces of iron, according to the kind 

 of tool to be made therefrom. The bars thus produced were cut up and manufactured 

 into the shape of the desired articles by forging. If the cutting edge was to extend 

 but a short distance, the steel was applied only near one edge of the pile. The com- 

 pound bars which have the steel on one side are suitable for chisels and other tools, 

 which have a cutting edge on one side, the iron being ground away when making or 

 sharpening the tool. See CUTLERY ; STEEL. 



EDULCORATE (Edulcorer, Fr. ; Aussussen, Ger.) is a word introduced by the 

 alchemists to signify the sweetening, or rather rendering insipid, of acrimonious pul- 

 verulent substances, by copious ablutions with water. It means, in modern language, 

 the washing-away of all particles soluble in water, by agitation or trituration with this 

 fluid, and subsequent decantation or filtration. 



EFFERVESCENCE. (Eng. and Fr. ; Aitfbrausen, Ger.) When gaseous matter 

 is suddenly extricated with a hissing sound during a chemical mixture, or by the 

 application of a chemical solvent to a solid, the phenomenon, from its resemblance to 

 that of simmering or boiling water, is called effervescence. The most familiar ex- 

 ample is afforded in the solution of sodaic powders ; in which the carbonic acid gas of 

 bicarbonate of soda is extricated by the action of citric or tartaric acid. 



EFFLORESCENCE (Eng. and Fr. ; Verwittcrn, Ger.) is the spontaneous con- 

 version of a solid, usually crystalline, into a powder, in consequence either of the 

 abstraction of the combined water by the air, as happens to the crystals of sulphate 

 and carbonate of soda ; or by the absorption of oxygen and the formation of a salino 

 compound, as in the case of alum schist, and iron pyrites. Saltpetre appears as an 

 efflorescence upon the ground and walls in many situations. 



EGGS. The eggs of birds become useful in many processes of manufacture. They 

 consist of four parts : 



1. The shell, consisting of 



Carbonate of lime 8 9 '6 



Phosphate of lime and magnesia . . . .57 

 Animal matter and sulphur 4' 7 



2. A immbranc (membrana putaminis) which lines the shell, which analysis shows 

 to be composed of 



Carbon . . 50*7 



Hydrogen 6'6 



Nitrogen . . . . . . . . 16-8 



Oxygen and sulphur 26'0 



3. The white. Albumen, a colourless liquid, enclosed in large cells formed of a thin 

 membrane. 



4. The yolk, or wtellum. Surrounded by the albumen ; also enclosed in a membrane. 



The albumen, or white-of-egg, is used for numerous purposes in the arts. It con- 

 tains carbonates in variable quantity, albumen, a small quantity of fat, glucose, and 

 extractive matter. 



The yolk of birds' eggs consists mainly of fat and pigment. See Watts's ' Dic- 

 tionary of Chemistry.' 



Eggs, non-incubated, respire, giving off water and carbonic acid, and absorbing 

 oxygen, so that the air confined at the broad end of the egg is richer in oxygen than 

 the external air. This indicates the method to be adopted in the preservation of 

 eggs, viz., to fill the pores of the shell, so as to prevent entirely the osmose force to 

 which this process of respiration belongs. If the eggs are dipped into melted tallow 

 or wax, or into a cream of freshly-slaked lime, this is effected. Dipping eggs into a 

 .strong brine is said to bo effectual ; the effects are similar in either case. The trade 

 in eggs is large. 



The Importation of eggs in the last five years was as follows : 



