On the Eggs of Cuvioca Mercenaria. 467 



great advantage of the reflecting telescope. The light of the 

 silvered mirrors is not indeed perfectly white;, but it is a 

 curious coincidence that the defect is very similar in quality to 

 $hat of a well-corrected (i.e., in technical language, over-cor- 

 rected) achromatic, a portion of the blue rays being in either 

 case separated, and so giving a slight complementary orange tint 

 to the remainder. The difference, however, is that in the achro- 

 matic they are visible, and with high powers obtrusive, as a 

 luminous fringe ; in the silver film they disappear from trans- 

 mission, so as to leave the image clean. 



Occultation. — July 11th. 7] Libras, 6 mag., lOh. 15m. to 

 llh. 25m. 



OX THE EGGS OF CORIXA MERGE NAM A. 



BY DR. T. L. PHIPSON, E.C.S., 

 Member of the Chemical Society of Paris, etc. 



The egQ*s of the Mexican insect Gorixa mercenaria (Say), are 

 interesting, in the first place, because they form an aliment 

 extensively used by man ; in the second, inasmuch as they 

 contribute to the oolitic structure of certain fresh water lime- 

 stones of modern formation. In speaking of this insect pro- 

 duction in another place,* I stated with regret that these eggs 

 had not yet been submitted to chemical analysis. When the 

 Mexican traveller, M. Virlet d'Aoust, returned to Paris, he 

 placed in my hands a certain quantity of them, but the greater 

 portion I also distributed among my friends. Recently I have 

 examined, microscopically and chemically, what remained of 

 my specimen, and though the quantity was very small, some 

 unexpected results have been obtained. 



For ages the Mexicans have consumed great quantities of 

 these eggs ; they find them strewed by millions upon the 

 reeds which grow on the banks of the great fresh-water 

 lakes Texcocco and Chalco. The mode of collecting them is 

 very simple ; they are shaken from the reeds into a cloth, and 

 set to dry in the sun, after which they are ground like Hour, 

 placed in sacks, and sold to the inhabitants, who make the 

 flour into a kind of cake called hautle. The eggs themselves 

 are spoken of as Agauile, and before being ground are used to 

 feed chickens. 



It was interesting to ascertain by analysis whether this 

 substance is more or less nutritious than our bread, and, at 

 first sight, it would appear to be infinitely more so. 

 * Tie Utilization of Minute Life, p. 104. 



