POPULAR MISCELLANY. 



693 



retical inference. Tlie first experiment was 

 rather surprising. A glass cylinder placed 

 over an electric lamp (Foucault's regulator) 

 for two minutes, and afterward examined, 

 was seen to contain a perceptible amount 

 of red fumes, due to peroxide of nitrogen 

 (N20i). The air surrounding the lamp 

 was next drawn through a solution of pot- 

 ash, and the amount of nitric acid esti- 

 mated; this gave ten to twelve grains of 

 nitric acid produced per hour (it may even- 

 tually prove to be more, the difficulty being 

 to collect the whole of it). The next step 

 in the research will be to examine the va- 

 rious forms of electric light, with a view to 

 determine the amount of nitric acid pro- 

 duced by each. 



In an Ants' Nest. — The columns of the 

 Popular Miscellany from month to month 

 give evidence of the interest with which 

 naturalists study the ways of ants. Indeed, 

 the life-history of that interesting insect 

 seems to be full of surprises for the perse- 

 vering observer. Here is an account of a 

 nest of Formica nigra, in which a number 

 of Termites were kept as slaves. While 

 entomologizing in Portugal in 1877, in the 

 neighborhood of Cintra, Mr. Henry 0. 

 Forbes found a nest of F. nigra under a 

 stone. On turning the stone over, he ob- 

 served great consternation in the commu- 

 nity, evidently caused by the fear lest a 

 colony of Termes lucifugus, which the For- 

 micas had enslaved, should escape. The 

 Nigras instantly began seizing the Termites, 

 driving them underground by the nearest 

 orifices, in the mean time wrenching and 

 pulling off their wings. In the nest there 

 was also a large number of Termite larvae, 

 and the great object of the Nigras seemed 

 to be to get these underground as speedily 

 as possible. The ants fell on them with 

 fierce impetuosity, seizing them anyhow and 

 anywhere, dragging them against the most 

 strenuous opposition into the nearest aper- 

 tures of the underground home. Very often 

 this opposition resulted in a long and sav- 

 age fight, in which the larvas were badly 

 wounded, being deprived sometimes of their 

 antenna?, sometimes of half their jaws, and 

 not seldom killed outright. Occasionally, 

 however, the larvae were victorious, beating 

 off the Formicas. The observer saw at the 



end of a long fight one larva drawn by 

 its antennae, while it strenuously held on to 

 a small ball of earth which had proved a 

 vain anchorage for its feet, for larva and 

 clod together were dragged for a long dis- 

 tance through the grass. At last it seized 

 one stalk so firmly that its enemy could not 

 drag it farther ; whereupon, after recon- 

 noitering the ground for a little distance, 

 the latter disappeared, but shortly returned 

 with a companion, by whose aid the larva 

 was detached. This done, the helper went 

 his way, while the abductor proceeded with 

 his captive till lost to view. 



Pearls and their Origin. — People are 

 still to be found who believe in the myth 

 which ascribes to pearls a sort of animal 

 nature — being born of other pearls, feeding 

 like other animals, and growing larger by 

 the conversion of food into their own sub- 

 stance. A glass tube purporting to con- 

 tain some of these growing pearls and cer- 

 tain "grains of rice," on which they fed, 

 was lately sent from Australia to Mr. Frank 

 Buckland, who in turn placed it in the hands 

 of a competent conchologist, Mr. Hugh 

 Owen, for examination. Mr. Owen, honestly 

 desirous of dissipating the crass ignorance 

 which alone makes belief in such absurdi- 

 ties possible, takes the trouble to state 

 briefly, in "Land and Water," the natural 

 history of pearls, in substance as follows : 

 Pearls are concretions found either attached 

 to the interior of certain bivalve shells, or 

 enveloped in the folds of the mantle of the 

 animal that inhabits the shell ; the latter 

 are most valued. All pearls are formed 

 of the same substance as that lining the 

 inner surfaces of the shells in which they 

 are formed. The peculiar luster is caused 

 by alternate layers of thin membrane and 

 carbonate of lime, and depends on very 

 minute undulations of the layers. The 

 most valuable pearls are found in the soft 

 portions of the mollusca, and are believed 

 to be originally a grain of sand, or some 

 other irritating substance, which the ani- 

 mal covers with a nacreous deposit. That 

 this is the correct theory is seen on cut- 

 ting or slitting pearls, when each one is 

 found to have a foreign body as a nucleus. 

 Such being the natural history of pearls, the 

 story of " young pearls feeding on rice " 



