Manchester Memoirs, Vol. xlvi. (1902), No. 0. 3 



Whilst employing the open arc, however, several 

 interesting observations were made, which may be worth 

 while recording. 



In the first place, supports of carbon can be used with 

 advantage for bringing the quartz into the flame, but it is 

 necessary that the carbon used for these supports, as also 

 the carbons used for the arc, be as pure as possible, or 

 else the quartz may be contaminated by the ash which 

 falls upon it ; for the supports I have throughout made 

 use of graphitic carbon prepared in the electric furnace, 

 which is very pure and easy to work ; it can, moreover, 

 now be obtained on the market at a reasonable price. 



In building up small rods, grooves were cut in a 

 plate of this carbon and small pieces of prepared quartz 

 were placed in these grooves, the quartz being melted 

 together gradually from one end to the other of the 

 grooves, by sliding the carbon plate gradually under 

 the arc-flame. Small lens-shaped discs can be similarly 

 prepared by placing pieces of the prepared quartz in 

 a shallow carbon crucible, and, with a little practice, 

 it is hoped that masses suitable for making lenses can 

 be prepared in this way. The valuable optical properties 

 of fused quartz are pointed out by Shenstone in his 

 papers/ 



When quartz is thus fused in the arc, it is quite easy 

 to observe the reduction which takes place in the imme- 

 diate neighbourhood of the arc, and causes a black stain 

 on the surface, which can easily be made to disappear by 

 bringing the heated mass for a short time away from the 

 centre of the flame ; in fact, the working of quartz in the 

 arc-flame much resembles the working of lead glass in 



^ It should be mentioned that Messrs. Zeiss, of Jena, exhibited small 

 lenses at the Paris Exhibition in 1900, made of " crystal de roche fondu,'" 

 but the method by which the quartz was fused was not stated. 



