320 QUARTZ FIBERS. 



to their size, and surpasses that of ordinary bar steel, reaching, to use 

 the language of engineers, as high a figure as 80 tons to the inch. Fibers 

 of ordinary size have a strength of 50 tons to the inch. 



While it is evident that these fibers give us the means of ])ro(lucing 

 an exceedingly small torsion, and one that is not affected by weather, 

 it is not yet evident that they may not show the same fatigue that 

 makes spun glass useless. I have therefore a duplicate apparatus with 

 a quartz fiber, and you will see that the spot of light comes back to 

 its true place on the screen after the mirror has been twisted round 

 twice. 



I shall now for a moment <lraw your attention to that peculiar property 

 of melted quartz that makes threads such as I have been describing a 

 possibility. A liquid cylinder, as Plateau has so beautifully shown, is 

 an unstable form. It can no more exist than can a pencil stand on its 

 jjoint. It immediately breaks up into a series of spheres. This is well 

 illustrated in that very ancient experiment of shooting threads of resin 

 electrically. When the resin is hot, the liquid cylinders which are pro- 

 jected in all directions break up into spheres, as you see now upon the 

 screen. As the resin cools they begin to develop tails ; and when it 

 is cool ejiough, *. e., sufficiently viscous, the tails thicken, and the beads 

 become less, and at last uniform threads are the result. The series of 

 photographs show this well. 



There is a far more perfect illustration which we have only 

 to go into the garden to find. Tliere we may see in abundance 

 what is now upon the screen — the webs of those beautiful geo- 

 metrical spiders. The radial threads are smooth, like the one 

 you saw a few minutes ago, but the threads that go round 

 and round are beaded. The spider draws these webs slowly, 

 and at the same time pours upon them a liquid, and still 

 further to obtain the eflect of launching a liquid cylinder in 

 space he, or rather she, pulls it out like the string of a bow, 

 and lets it go with a jerk. The liquid cylinder can not exist, 

 and the result is what you now see upon the screen (Fig. 8). 

 A more perfect illustration of the regular breaking up of a 

 liquid cylinder it would be impossible to find. The beads 

 are, as Plateau showed they ought to be, alternately large 

 and small, and their regularity is marvellous. Sometimes 

 two still Smaller beads are developed, as may be seen in the 

 second pliotograph, thus completely agreeing with the results 

 of Plateau's investigations. 



I have heard it maintained that the spider goes round her 



web and places these beads there afterwards. But since a 



Fig. 8. ^e\3 y^n]^ about 360,000 beads is completed in an hour — that 



is, at the rate of about 100 a second — this does not seem likely. That 



what I have said is true, is made more probable by the photograph of 



