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THE POPULAR SCIENCE MONTHLY 



but this ho shows to be impracticable ; 

 the other method is to use part of the 

 power of the engine to pump back the dis- 

 charged steam, containing as it does some 

 water condensed from the steam, into the 

 boiler. This latter method is theoretically 

 practical, and the purely mechanical diffi- 

 culties in the way of its realization are by 

 no means insuperable. 



As the steam in the cylinder of an en- 

 gine expands, doing work, part of it con- 

 denses. The difference between the heat- 

 energy of the steam at the beginning of the 

 stroke, and that of the steam and water at 

 the end of the stroke, is equal to the heat- 

 equivalent of the mechanical work done by 

 the steam. The change of mechanical con- 

 dition which the steam undergoes during 

 the stroke namely, its conversion into 

 water renders it possible that the mingled 

 steam and water remaining in the cylinder 

 at the end of the stroke may be forced 

 back into the boiler with a less expenditure 

 of mechanical energy than the steam gave 

 out during the stroke. 



The Telephone anticipated. As is the 



case with all great inventions, the tele- 

 phone is now said to be nothing new ; its 

 principle was known long ago, and even ex- 

 emplified in practice. Many are the claim- 

 ants of priority in solving the problem of 

 the transmission of articulate sound to great 

 distances, but we know of none whose case is 



stronger than that of " Monsieur Ch. B ," 



who appears to have solved the problem as 

 early as 1857. In the Count du Moncefs 

 "Expose des Applications de l'Eleetricite," 

 published twenty years ago, occurs the fol- 

 lowing passage (translated in Nature) : 



"After the marvelous telegraphs which are 

 able to reproduce at a distance writing of this 

 or that individual, and designs more or less com- 

 plicated, it seemed impossible, said M. B , 



to advance further in the regions of the mar- 

 velous. Nevertheless, essaying to do something 

 more, I asked, for example, if speech itself 

 would not be capable of transmission by elec- 

 tricity ; in a word, if one would not be able to 

 speak at Vienna and be heard at Paris. The 

 tiling is practicable. This is how: Sounds, it 

 is known, are formed by vibrations and carried 

 to the car by these same vibrations, which are 

 reproduced by the intermediate media. But the 

 intensity of these vibrations diminishes very 

 rapidly with the distance, from which it follows, 

 even in the employment of speaking-trumpets, 

 tubes, and of acoustical horns, the limits which 



cannot be surpassed are very restricted. Im- 

 agine that one speaks near a mobile plate, flexible 

 enough not to lose any of the vibrations produced 

 by the voice; that this plate establishes and inter- 

 rupts successively the communication with a bat- 

 tery. Ton would be able to have at a distance 

 another plate which would execute at the same 

 time the same vibrations. It is true that the in- 

 tensity of the sounds produced would be variable 

 at the point of departure, where the plate is vi- 

 brated by the voice, and constant at the point of 

 arrival, where it is vibrated by electricity. But 

 it is demonstrable that this would not alter 

 the sounds. ... In any case, it is impossible to 

 demonstrate that the electric transmission of 

 sounds is impossible. ... An electric battery, 

 two vibrating plates, and a metallic wire, will 

 suffice." 



The Slaves of Ants. The subjugation of 

 other insects by various species of ants is 

 a familiar fact of natural history ; it is less 

 usual to see two or more species thus sub- 

 jugated. Prof. Leidy, in some remarks 

 made at a meeting of the Academy of 

 Natural Science of Philadelphia, recounts 

 his observations on a colony of yellow ants 

 {Formica fiava), which had three different 

 insects in their service, namely, a species 

 of Aphis, a Coccus, and the larva of an in- 

 sect, probably coleopterous. The aphides, 

 he tells us, were kept in two separate herds, 

 and these were separated from a herd of 

 cocci. The larva was in the midst of one 

 of the former herds. In another and larger 

 colony of yellow ants there was a herd of 

 aphides which occupied the under-part of 

 one margin of the stone under which the 

 ants had their nest; the surface occupied 

 by these aphides was about ten inches long: 

 and three-fourths of an inch broad. The 

 same colony also possessed a separate herd 

 of cocci, closely crowded, and occupying al- 

 most a square inch of space. Both aphides 

 and cocci, with few exceptions, adhered to 

 the under-surface of the stone, and were 

 not attached to the roots. They appeared 

 to be carefully attended by the ants, which 

 surrounded them. The larva, too, was care- 

 fully attended by the ants, which were fre- 

 quently observed to stroke it with their 

 antennae. The aphides and cocci were all 

 in good condition, but without visible means 

 of subsistence, excepting the neighboring 

 grass-roots partially extending into the 

 earth beneath the stones, to which they 

 probably were at times transferred by their 

 masters. 



