PHYSICS 465 



flow incessantly through the siphon, and regaining the vessel be engaged 

 in perpetual circulation. As a matter of fact, however, the water is drawn 

 upwards in the vertical portion of the tube, until its free surface reaches 

 a certain portion of the oblique part of the same tube, when it stops. 

 The author accounts for these results by suction, exerted by the small 

 concave liquid surface between the two tubes. {Nature, April, xxv, p. 

 614; PMl. Mag., May, Y, xiii, p. 379.) 



Wroblewsky has studied the influence which the quantity of gas dis- 

 solved in a liquid has on its superficial tension, and concludes that, in 

 the case of carbon dioxide, there is a remarkable relation between the 

 laws of its solubility in water and the superficial tension of the liquid. 

 This relation he expresses thus : 1st. The product of the surface ten- 

 sion a by the pressure P under which the gas is confined, is propor- 

 tional to the coefficient of saturation S, which corresponds to this press- 

 ure. 2d. The pressure remaining constant and equal to n atmospheres 

 {n being greater than unity), it results from the laws of solubility that 

 the quotient 



Cpy P = n ^Qpjp = l 



diminishes with the lowering of the temperature. Experiment shows 

 that in this case the ratio of the tensions corresponding to these press- 

 ures diminishes also. {Comptes Bendus, August, xcv, 284.) 



Sresnevsky has measured the cohesion of aqueous solutions of zinc 

 chloride by the two methods of Quincke: 1st, measuring the height of 

 the liquid in a capillary tubej and 2d, observing the flat bubbles of air 

 on the surface of the liquid, covered with a glass. As a mean he finds 

 that the cohesions respectively of 8.00 mgrms., of 8.77 mgrms., and of 

 8.71 mgrms. correspond to solutions of 83 per cent., 46 per cent., and 20 

 per cent, of chloride of zinc. {J. Soc. Fliys. Gliim. Busse, xiii, p. 242 ; J. 

 Phys., December, II, i, p. 576.) 



Elie has contrived an apparatus for studying the laws of the flow of 

 liquids in tubes, which is at once simple and sensitive. It is a sort of 

 Wheatstone's bridge; the liquid coming from a reservoir divides and 

 passes through the two tubes to be compared. At the point where they 

 join the main tube two other tubes pass toward each other and termi- 

 nate in a flask, a thin film of metal being suspended between their ends. 

 If the two branches are identical in resistance, there is no flow through 

 the lateral tubes, and the film remains motionless. Hence when the 

 film is motionless the same quantity of liquid passes through each tube. 

 The same arrangement acts admirably with gases. {J. Phys. , October, II, 

 I, p. 459.) 



A rheometer for measuring currents of water, at different depths, 

 has been devised by Scardona. The water current acts on two screw 

 vanes on a horizontal shaft in a case attached to a vertical rod. A flat 

 vane keeps this shaft parallel with the current, and at intervals it actu- 

 ates, by means of an endless screw and wheel- work, a lever attached to 

 H. Mis. 26 30 



