Chemistry and Physics. 489 



In front of the opening of a tube of Kundt, is placed a second 

 open tube, giving the same sound as the first, and suspended by 

 two threads. Making the first tube resound loudly, the second 

 tube is strongly repelled. The sarae efiect is obtained if the sec- 

 ond tube gives one of the harmonies of the first. Placing two tubes 

 facing each other opposite the tube of Kundt and perpendicular to 

 its axis, they tend to approach each other. With a very sensitive 

 manometer it appears that in a column of air in a state of perma- 

 nent vibration, the air at the nodes has an excess of pressure. 

 This accounts for the heaping up of water in the loops of a tube of 

 Kundt, It is explained by admitting that the amplitude of the 

 vibrations cannot be neglected compared with their length. It fol- 

 lows that there ought to be a continuous motion of the air from 

 a node to a loop. This might be proved by filling the resonant 

 box of a tuning fork with the fumes of chloride of ammonium and 

 seeing if they are thrown out when the fork is set in vibration. 



If a bell is filled with water and a drop of oil allowed to fall on 

 it, the circular film becomes quadrangular when the bell is sounded. 

 The water-currents start from the nodes and accumulate at the 

 loops. A disk of glass is attached to the end of a rod vibrating 

 longitudinally. If a glass drop is hung opposite the disk it will be 

 repelled at the center and attracted around the periphery. There 

 are then, as with air, currents outward at the center, and counter 

 currents inward along the edges. — Journ. de Fhys.^v, 122. 



15. Correlation of Forces.— M. Geoye describes a convenient 

 apparatus for showing the relations between heat, electricity, and 

 mechanical force. The arrangement is as follows: 



Two of Clamond's thermo-electric generators are connected for 

 quantity and put in communication with a gram machine, in 

 such a way as to set this in motion. In the circuit is inserted a sort 

 of electric lamp, in which a platinum wire, placed in the center of 

 a small globe (which protects it from agitation of the air) can be 

 raised to incandescence. The only difficulty of the experiment 

 consists in so regulating the length and diameter of the platinum 

 wire, that it may be raised to a red heat while the thermo-electric 



A circuit entirely metallic is thus obtained, with which the fol- 

 lowing transformations can be effected ; 



(1.) The gram machine being excluded from the circuit, a por- 

 tion of the heat, transformed into electricity by the thermopile, 

 reappears as heat in the wdre. 



(2.) The wire being excluded from the circuit and the machine 

 introduced, a portion of the heat, transformed into electricity in 

 the pile, reappears as work in the machine. 



(3.) The wire and machine bein^ included in the circuit, a part 

 of the heat, transformed in the pile into electricity, produces heat in 

 the wire and work in the motor. If we then stop the machine, the 

 of the wire is increased. The machine being libera- 



