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THE POPULAR SCIENCE MONTHLY. 



by different investigators to reside in the thin envelope of the 

 water-drop ; acoustic energy by M. Savart, as noticed in a cascade 

 of water-drops, the envelopes of which underwent rhythmical 

 deformations ; calorific energy, due to the displacement of mole- 

 cules that pass from the surface to the ranks, or which ascend to 



the superficial layer; luminous 

 energy, as studied by Newton, 

 Boyle, Hooke, Young, and Fres- 

 nel ; and electrical energy, as 

 manifested in effects that have 

 been observed by M. Lipmann — 

 all of which, according to M. 

 Gossart, are transformable one 

 into another in accordance with 

 the law of conservation of force. 

 A drop of water hangs from 

 a leaf or the eaves of a house, 

 held up as in a bag by its su- 

 perficial envelope. It continues 

 to increase in size and weight 

 many times faster than the ten- 

 sion of its cordon of attachment 

 is re-enforced, till it overcomes 

 that tension, and then it falls ; 

 and, according to M. Gossart, 

 all the drops of water that fall — 

 of themselves — are of the same 

 size. The drops of melted metals, whose superficial tensions are 

 enormous, reach correspondingly enormous magnitude. The pu- 

 rity of liquids can be determined by observing the size of the 

 drops they give ; in the case of wines, by counting the number of 

 drops per cubic centimetre ; for the superficial tension of all 

 liquids is modified by adulteration. 



M. Van der Mensbrugghe has calculated what he calls the 

 potential energy of water, on the basis of the estimation of its 

 superficial tension at 7'5 milligramme-millimetres per square milli- 

 metre of free surface. This is resident in a film not more than 

 2~5Y5iro of a millimetre thick. Distributed over the whole ocean, it 

 gives an amount of mechanical force which we have no means 

 of accurately calculating. If we suppose that of two equal and 

 adjacent superficial layers of sea-water, one washes over the other 

 by the effect of the wind, for example, the layer that is covered 

 loses its free surface, and with it its proper potential energy, 

 which appears again in an increase of speed. Thus on the 

 ocean the action goes on, the energies of the successive waves 

 being extinguished as to them and transferred to others ; so that 



Pig. 9 —Levels to which Water will rise in 

 Capillary Tubes charged, respectivelt, 

 with Air (A), Vapor op Ether (E), and 

 Camphor-Vapor (C). 



