GOSSAMER 295 



effected. The threads are prepared (for use in suspending 

 swinging bars in delicate measurements of force) of a 

 thickness of y^thnrth of an inch. Some have been made 

 so fine as to be not only invisible to the naked eye, but 

 to be only vaguely indicated by the highest powers of the 

 microscope. They are estimated to be only one-millionth 

 of an inch in diameter. It is difficult to form any mental 

 picture or conception of these finest quartz threads spun by 

 Mr. Boys. But the following fact helps us to realise how 

 delicate they are. A grain of sand just visible to the eye 

 that is to say, T^th of an inch long, the same in breadth, 

 and the same in height would make twenty miles of such 

 thread. 



