and some suggested Uses of the Finest Threads. 491 



do not seem to be of any practical use. It is possible, how- 

 ever, that this method might be available for reducing to a 

 fine state of division such of the rosins or other easily fusible 

 bodies as cannot readily be powdered mechanically. 



On returning to bodies which, like glass, require a high 

 temperature for their fusion, to which the electrical method is 

 inapplicable, we find that the only method practically available 

 is that of drawing mechanically. It would seem that if finer 

 threads than can be formed by the ordinary process of glass- 

 spinning were required, it would be necessary to obtain a 

 higher speed, to have the glass hotter, and to have as small a 

 quantity as possible hot. I put this idea to a test by mounting 

 at the back of a blowpipe-table a pair of sticks which could be 

 suddenly moved apart by a violent pull applied to each near 

 their axes. By these means the upper ends were separated 

 about 6 feet, and the motion was so rapid that it was impos- 

 sible to follow it. A piece of glass drawn out fine was 

 fastened to the end of each stick, and the ends of these heated 

 by a minute blowpipe-flame. They were immediately made to 

 touch and allowed to fly apart. In this way I obtained threads 

 of glass about 6 feet long, finer than any spun glass I have 

 examined. By using the oxyhydrogen jet with the same 

 apparatus, still finer threads were produced. It was evident 

 then that the method was right ; but some more convenient 

 device which also would make long threads would be prefer- 

 able. 



There are several ways of obtaining a high speed, the most 

 usual depending on an explosive ; but it would be difficult to 

 arrange in a short time a gun which could be used to shoot 

 a projectile carrying the thread which would not also destroy 

 the thread by the flash. It is possible that an air-gun could be 

 so arranged. Rockets when at the period of most rapid com- 

 bustion have an acceleration which is enormous. Thus a well- 

 made 2-oz. rocket is at one part of its flight subject to a 

 force of over 3 lb. in gravitative measure. This force, acting 

 on such a body for 10 seconds only, would, neglecting atmo- 

 spheric resistance, starting from rest, carry it more than 6 miles. 

 The acceleration is about 28 times that due to gravity on the 

 earth, or about the same as that on the sun. Anyone who 

 will stay in a room with a lighted two-ounce rocket, having 

 no stick or head, will obtain a more vivid notion of the value 

 of gravity on the sun than in any other way I know. 



A rocket is perhaps more available for thread-drawing than 

 a gun, but it does not seem altogether convenient. One 

 other method, however, is so good in every respect, that there 

 seems no occasion to try a better. The bow and arrow at 



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