142 ANNUAL KECORD OF SCIENCE AND INDUSTRY. 



gin decreases very rapidly, and at the margin itself is perhaps 

 at zero. In cases of straight margins of great length there 

 is a constant surface motion from the margin toward the cen- 

 tre, most intense at the margin. The average central surface 

 velocity varies on a calm day nearly as the square root of the 

 central depth. The curve representing the mid-channel ver- 

 tical velocity is approximately a common parabola, whose 

 axis is usually below the surface at a depth depending upon 

 the state of the wind ; but the form of the curve is hardly 

 well enough determined to admit of inferring the bottom ve- 

 locity. The line of maximum velocity is highest at mid-chan- 

 nel, and deeper as we proceed toward the margins. Profes- 

 sional Papers on Indian Engineering ^ October, 1875. 



gauss' theoey of capillarity. 



Plateau states that, as is well known. Gauss has deduced 

 formulae relative to particular phenomena of capillarity, by 

 starting from the principle of virtual velocities. The French 

 scientist Moutier has recently shown that the theory of 

 Gauss properly treated explains certain effects attributed 

 of late years to the tension of liquid surfaces, without any 

 necessity of especially assuming the existence of such tension. 

 He has deduced also a general formula concerning the equi- 

 librium of two liquids in contact with each other and with a 

 solid. This formula contains certain constants relative to 

 the different molecular attractions that obtain in the system ; 

 and now Van der Mensbrugghe, of Ghent, demonstrates that 

 these constants themselves have a definite physical signifi- 

 cation ; that they represent, viz., respectively the tension at 

 the free surface of the two liquids, the tension at their com- 

 mon surfiice, and the tensions at the surfaces of contact be- 

 tween the liquids and the solids. Bulletin Acad. Poyale des 

 /Sciences de Pelgiqice, 1875, 366. 



lippmann's experiments ox capillary attraction and 

 HIS electro-capillary motor. 



The facts in relation to capillary attraction, described by 

 Mr. Lippmann, and of which he has availed himself in the 

 contrivance of what he calls the electro -capillary motor, 

 now exciting so much attention in Europe, are not original 

 with him, but are due to Dr. Draper, who discovered them 



