276 WITHDRAWN FROM THE ACTION OF GRAVITY. 



held a little obliquely was plunged to tlie bottom of a vessel containing glyceric 

 liquid, and by continued blowing a numerous series of bubbles of quite large 

 size were made to traverse tbe liquid. This occasioned, as is done by children 

 with soap-bubbles, the formation of a partitioned mass rising above the edge of 

 the vessel, a mass evidently of the same constitution with froth, but of which 

 the different parts have much larger dimensions. Now, as far as the eye could 

 penetrate, without embarrassment, into this system, it was observed that every- 

 where the same edge was common to only three partitions, and that there were 

 never more than four edges terminating at the same point. As regards the 

 equality of the angles between these edges, there were certain places where 

 three of those which terminated at one point seemed to be nearly in the same 

 plane ; but, on looking more attentively, it was ascertained that these edges were 

 strongly Inflected in approaching their point of concourse. 



The generation of such a mass, and consequently that of froth, is easily ex- 

 plained. The first bubbles of gas which reach the surface of. the liquid give 

 rise to spherical caps, which form groups like those with which we have been 

 previously occupied, and presently the whole surface of the liquid is covered 

 with them ; the films produced by the subsequent gaseous bubbles necessarily 

 lift up this first assemblage, by occasioning the formation of partitions beneath, 

 so that, in a short time, there are two systems of superposed films, and the gas- 

 eous bubbles continuing to arrive, this assemblage is elevated in its turn, and so 

 in succession, the whole arranging itself with more or less symmetry, according 

 to the differences of volume of the successive gaseous bubbles, and the distri- 

 bution of the points where they attain the surface of the liquid, and the slight 

 edifice composed of partitions imprisoning within the spaces which they sepa- 

 rate all the volumes of gas which respectively constituted the bubbles, acquires 

 greater and greater height. If the bubbles are very minute, the partitioned 

 edifice will be composed of parts too small to be in general distinguished by the 

 eye, and in that case there is froth. 



§ 23. Let us return now to the laminar systems of the frames and complete 

 their study. We will first see how the films which proceed from each of the 

 solid edges are generated, and for this let us take a very simple example. Sup- 

 pose that one of the upper rings of § 14 of the 5th series, that is to say, a hori- 

 zontal ring of iron wire, sustained, like our frames, by a fork, be plunged into 

 soap^water or glyceric liquid, and then withdrawn with due quickness, while 

 kept always parallel with the surface ; as long as the distance from the ring to 

 the plane of the liquid is very small, the liquid will rise a little, by capillary 

 action, presenting, at the exterior and interior of the ring, two small surfaces 

 with concave meridian curvatures. Now, it is easy to see that in proportion as 

 the ring continues to ascend these two small surfaces will become more and 

 more concave in a meridian direction. We know, in effect, that when we raise 

 a solid disk previously brought into contact by its under face with the surface 

 of a liquid capable of moistening it, the portion of this liquid raised by the disk 

 above the exterior level soon presents, in the meridian direction, a concavity 

 which increases in proportion as the disk rises. The same thing, then, must 

 also take place with regard to that one of our small surfaces which faces out- 

 wardly, and it is clear that the other small surface, that, namely, which faces 

 the interior space of the ring, must, for the capillary equilibrium of the little 

 mass raised by this ring, undergo analogous modifications. 



Our two small surfaces, will continue, therefore, mutually approaching as the 

 ring ascends until they nearly touch one another. But they cannot thus ap- 

 proach without expelling a portion of the liquid comprised between them; now, 

 if the ascension of the ring is not too slow, the viscosity and cohesion of the 

 liquid will act here as in the case of § 1, and for the same reasons there will be 

 formed a film, which will extend between the small portion of liquid that 

 remained suspended along the ring and the small annular mass elevated at the 



