Attachment of Quartz Fibres. 465 



or capillarity will give trouble somehow. With the rapid 

 movement the little weights hardly acquire any pendular 

 motion. 



4. After a minute or two do the same, but to a slightly 

 greater depth, with water which may be distilled. 



5. When the acid may be supposed to be washed off, im- 

 merse in the same way in Rochelle salt silvering-solution 

 (Kohlrausch, ' Physical Measurements/ p. 115). 



6. Wash as in 4. 



7. Fill a glass with the copper solution that is employed in 

 electrolytic measurements of current, i. e. not saturated, and 

 slightly acid. Dip the extreme point of the positive wire from 

 a single cell into the liquid, and with a clean smooth negative 

 wire take the hanging ends, one at a time, and having made 

 the contact outside the glass by resting the upper part of the 

 silver coat upon the wire, let down into the solution, keeping 

 the fibre in gentle movement on the wire and making it dip 

 more and less in the liquid. In a few seconds the little 

 weight will be bright red, and the immersed portion of the 

 silvered coat will be bright red also. The silver coat has 

 sufficient resistance to prevent unduly rapid deposition. Do 

 the same to the other end. 



8. Cut off to length, allowing about 5 millimetres at each 

 end for the junction. Take tags of copper-foil three or four 

 centimetres long and three or four millimetres wide, tapering 

 to a point, and having tinned the pointed end of each with 

 the minimum of solder, again wet with chloride-of-zinc 

 solution. On the wet surface lay the coppered end, taking 

 care that it points in the right direction. Capillarity will 

 now hold it. Rapidly heat the copper to the melting-point 

 by holding a point about one centimetre from the narrow end 

 over a minute flame. The solder will flash and envelope the 

 coppered fibre. Cut off the tag of the desired length, holding 

 the metal by the tag with a pair of pliers and not by the 

 heavy end. 



9. Wash in boiling water as in 4 to remove chloride of 

 zinc. The fibre is now attached, but the protruding silver 

 and copper give a want of defmiteness in the place of 

 attachment. 



10. Dip up to the point of the tag in melted beeswax, 

 following the precautions given in 3, but the two tags may 

 be more conveniently dipped separately. 



11. Dip up to the top of the copper and silver in strong 

 nitric acid. 



12. Wash in boiling water, which removes acid and bees- 

 wax and leaves the fibre readv for use. 



