260 THE SCHOOL OF R:eAUMUR 



A Digression on Eggs^ 



What he had seen of the retarded development of 

 insect-eggs put it into Reaumur's head to try whether 

 the eggs of fowls might not be kept fresh and capable of 

 development long beyond the ordinary term. The fowl's 

 egg spoils in consequence of putrefactive change ; if 

 such change could be hindered it might be possible to 

 keep the egg fresh for an indefinite time. 



What happens, he inquired, when an egg goes bad? 

 In spite of egg-shell and shell-membrane, the egg loses 

 moisture, and as it loses moisture it spoils. In a fresh 

 egg the contents fill the whole space, but a continually 

 increasing cavity, which can be seen by holding the egg 

 up to the light, is found in all stale eggs; it is due to 

 the loss of water by evaporation. Bellini and Vallisnieri 

 had proved that the egg-shell is porous, for when the 

 egg was placed in the receiver of an air-pump and 

 surrounded by boiled water, the air rushed through the 

 pores in the form of small bubbles. In the last days of 

 hatching the chick utters a cry, which proves that its 

 lungs are then filled with air ; this air must have 

 entered by the pores of the egg-shell. The countryman, 

 continues E^aumur, knows how to keep autumn-laid 

 eggs till winter, and then sell them as fresh eggs. He 

 packs them in barrels with close-pressed wood-ashes ; 

 the ashes choke the pores of the egg-shell, and render 

 evaporation slow. It occurred to Reaumur that varnish- 

 ing the eggs would be simpler and more certain. 

 Accordingly he took fresh-laid eggs in April, and 

 varnished them with shellac dissolved in alcohol ; next 

 day he varnished them a second time. After two and a 

 half months, that is, early in July, he boiled and 



* Vol. II, Mem. i. Issued as a separate work in 1749. 



