550 Mr. C. V. Boys [June 14, 



The result, then, is this. The smallness, the length of period, 

 and therefore delicacy, of the instruments at the physicist's disposal 

 have until lately been simply limited by the behaviour of silk. A 

 more perfect suspension means still more perfect instruments, and 

 therefore advance in knowledge. 



It was in this way that some improvements that I was making in 

 an instrument for measuring radiant heat came to a deadlock about 

 two years ago. I would not use silk, and I could not find anything 



else that would do. Spun glass, 

 ^i^- ^' even, was far too coarse for my 



purpose ; it was a thousand times 

 too stiff. 



There is a material, invented 

 by Wollaston long ago, which, 

 however, I did not try, because it 

 is so easily broken. It is platinum 

 wire which has been drawn in 

 silver, and finally separated by 

 the action of nitric acid. A speci- 

 men about the size of a single line 

 of silk is now on the screen, show- 

 ing the silver coating at one end 

 (Fig. 5). 



As nothing that I knew of 

 could be obtained that would be 

 of use to me, I was driven to the 

 necessity of trying by experiment 

 to find some new material. The 

 result of these experiments was the 

 development of a process of almost 

 ridiculous simplicity, which it 

 may be of interest for me to show. 

 The api^aratus consists of a 

 small cross-bow, and an arrow 

 made of straw with a needle point. 

 To the tail of the arrow is attached 

 a fine rod of quartz, which has 

 been melted and drawn out in the 

 oxyhydrogen jet. I have a piece 

 of the same material in my hand, 

 and now, after melting their ends 

 and joining them together, an operation which produces a beautiful 

 and dazzling light, all I have to do is to liberate the string of the bow 

 by pulling the trigger with one foot, and then, if all is well, a fibre 

 "will have been drawn by the arrow, the existence of which can be 

 made evident by fastening to it a piece of stamp-paper. 



In this way threads can be produced of great length, of almost 

 any degree of fineness, of extraordinary uniformity, and of enormous 



