22 OUR HUMBLE HELPERS 



story of the auxiliary birds I have already described 

 the eggs of the principal kinds. ' ' 



"I have taken care," interposed Jules, "to remem- 

 ber the curious variety of coloring that eggs have. 

 I recall very distinctly the nightingale's, green like 

 an olive ; the goldfinch's, spotted with reddish brown, 

 especially at the larger end; the crow's, bluish green 

 with brown spots ; and so many others that I hesitate 

 to say which are my favorites, so nearly equal are 

 they in beauty." 



"Let us learn now about the nature of the shell," 

 his uncle continued. "The substance of the shell is, 

 in the hen's egg, as white as marble ; its own color not 

 being disguised by any foreign pigment. This pure 

 white and its other characteristics, hardness and 

 clean fracture, do they not tell you of what sub- 

 stance the shell is composed?" 



"Either appearances deceive me greatly," an- 

 swered Louis, "or the shell is simply made of 

 stone." 



"Yes, my friend, it is indeed of stone, but stone 

 selected with exquisite care and refined as it were, 

 in the bird's body. 



"In its nature the eggshell does not differ from 

 common building-stone ; or rather, on account of its 

 extreme purity, it does not differ from the chalk that 

 you use on the blackboard, or from the magnificent 

 white marble that the sculptor seeks for the master- 

 pieces of his chisel. Building-stone, marble, and 

 chalk are at bottom the same substance, which is 

 called lime, limestone, or carbonate of lime. The dif- 



