V] OF SPIDERS' WEBS 233 



effect of the jerk being to disturb and destroy the unstable 

 equiHbriiim of the viscid cyhnder*. Another very curious 

 phenomenon here presents itself. 



In Plateau's experimental separation of a cyhnder of oil into 

 two spherical portions, it was noticed that, when contact was 

 nearly broken, that is to say when the narrow neck of the unduloid 

 had become very thin, the two spherical bullae, instead of absorbing 

 the fluid out of the narrow neck into themselves as they had done 

 with the preceding portion, drew out this small remaining part of 

 the liquid into a thin thread as they completed their spherical 

 form and consequently receded from one another : the reason being 

 that, after the thread or "neck" has reached a certain tenuity, 

 the internal friction of the fluid prevents or retards its rapid exit 

 from the little thread to the adjacent spherule. It is for the samfe 

 reason that we are able to draw a glass rod or tube, which we have 

 heated in the middle, into a long and uniform cylinder or thread, 

 by quickly separating the two ends. But in the case of the glass 

 rod, the long thin intermediate cylinder quickly cools and solidifies, 

 while in the ordinary separation of a liquid cylinder the corre- 

 sponding intermediate cylinder remains liquid ; and therefore, like 

 any other liquid cylinder, it is liable to break up, provided that its 

 dimensions exceed the normal limit of stability. And its length 

 is generally such that it breaks at two points, thus leaving two 

 terminal portions continuous with the spheres and becoming 

 confluent with these, and one median portion w^hich resolves itself 

 into a comparatively tiny spherical drop, midway between the 

 original and larger two. Occasionally, the same process of forma- 

 tion of a connecting thread repeats itself a second time, between 

 the small intermediate spherule and the large spheres ; and in this 

 case we obviously obtain two additional spherules, still smaller in 

 size, and lying one on either side of our first little one. This whole 

 phenomenon, of equal and regularly interspaced beads, often with 

 little beads regularly interspaced between the larger ones, and 

 possibly also even a third series of still smaller beads regularly 

 intercalated, may be easily observed in a spider's web, such as 

 that of Epeira, very often with beautiful regularity, — which 



* Cf. Boys, C. v., On Quartz Fibres, Nature, July 11, 1889; Warburton, C, 

 The Spinning Apparatus of Geometric Spiders, Q.J. M.S. xxxi, pp. 29-39, 1890. 



