192 M. G. Van der Mensbrugghe on the 



disturbing influence of the earth or other small planet has oc- 

 casioned are probably, for the most part, the debris of streams 

 which at one time were moving with a direct motion round 

 the sun. 



Since we have now abundant reason to believe that the great 

 circular stratum within which the members of the solar system 

 lie is traversed in all directions by numbers of these meteoric 

 bodies, so vast that, as Professor Newton has computed, 1\ 

 millions large enough to be visible to the naked eye on a clear 

 night, and 40 times that number of smaller ones, enter the earth's 

 atmosphere daily, we are no longer called on to assume the ex- 

 istence of a resisting medium, or of a departure from the law of 

 gravitation, to account for the retardation of comets. Meteors 

 passing through a comet indifferently in all directions and with 

 the same absolute speed, would operate upon it like a resisting 

 medium. 



XXV. On the Tension of Liquid Films. 

 By M. Gr. Van der Mensbrugghe*. 



IN my first investigation " On the Tension of Liquid Films" f, 

 I gave the laws which ought to be satisfied by the curve of a 

 flexible inextensible thread without weight, and acted upon at its 

 external surface simply by the contractile force of a liquid film in 

 a state of equilibrium. It will be remembered that one of these 

 laws is that the radius of curvature is the same at all points of 

 the line in question. On the other hand, the osculating plane 

 of the curve everywhere coincides with the tangent plane to the 

 laminar surface. Now, if these two properties be combined, a 



deflection as seen from the earth, and corresponds to an absolute deflection 

 in space of 2° 20'. 



On the other hand, in the case of a meteor overtaking and passing the 

 earth, 



_ 22400 1 _ 1 



a 524000 ' (0 4) 2 2-314 '' 

 therefore the maximum deflection as seen from the earth 

 = 2 cosec-* 3314=35°, 



which corresponds to an absolute deflection of 50°. 



The difference between these deflections far more than compensates for 

 the circumstance that the earth would come across, and therefore have an 

 opportunity of deflecting, about six times as many members of a retrograde 

 swarm of meteors as of a similar one travelling in a direct orbit. 



* Translated from the Bulletin de V Academe Royalede Belgique, ser. 2. 

 vol. xxiii. No. 5 (1867). 



t Bull, de VAcad. Roy. de Belgique, ser. 2. vol. xxii. p. 308. Phil. Mag. 

 vol. xxxiii. p. 2/0. 



