20 FIRESIDE SCIENCE. 



The shell of the egg is lined upon its interior 

 everywhere with a very thin but pretty tough 

 membrane, which, dividing at or very near the ob- 

 tuse end, forms a little bag which is filled with air. 

 In new-laid eggs, this follicle appears very small, 

 but it becomes larger when the egg is kept. In 

 breaking ah egg this membrane is removed with 

 the shell, to which it adheres, and therefore is re- 

 garded as a part of it, which it is not. 



The shell proper is made up mostly of earthy ma- 

 terials, oT which 97 per cent, is carbonate of lime. 

 The remainder is composed of two per cent, of ani- 

 mal matter, and one of phosphate of lime and mag- 

 nesia. Carbonate of lime is the same material of 

 which our marble quarries and chalk beds are com- 

 posed ; it is lime, or oxide of calcium, combined with 

 carbonic acid, and is a hard, insoluble mineral sub- 

 stance, which does not appear to form any portion 

 of the food of fowls. Now, where does the hen pro- 

 cure this substance with which to form the shell ? 

 If we confine fowls in a room, and feed them 

 with any of the cereal grains, excluding all sand, 

 dust, or earthy matter, they will go on for a time 

 and lay eggs, each one having a perfect shell, made 

 up of the same calcareous elements. Vauquelin, 

 the distinguished chemist, shut up a hen ten days, 

 and fed her exclusively upon oats, of which she 

 consumed 7,474 grains in weight. During this time 



