338 



Scientific Proceedintjy, luina.i Dwhltn Society. 



fixed cantilever, and carries a small gas jet, for which the nipple of a Primus 

 stove proved verj^ suitable. The position of this jet can be readily adjusted 

 both horizontally and vertically, so that when the arm on the left side of the 

 apparatus is raised the small flame is brought to a position midway between 

 the chucks. The swinging framework is sufficiently flexible to enable the flame 

 to be moved towards either chuck by applying a slight side pressure to the 

 operating arm. 



The construction of the chucks is best shown in fig. 3, which is drawn to 

 scale, actual size ; one of them is shown in section. Each consists of a piece of 

 steel rod, 14 mm. long by 63 mm. (^") diameter, with a central hole, which for 

 the greater part of its length is 32 mm. (^") in diameter, but at one end is 

 contracted to 17 mm., thus forming an internal shoulder. A piece of rubber 



Fig 1. 



i'lG. 2. 



cycle-valve tubing, 65 mm. long, fits inside the larger part of the hole, and may 

 be pressed against the shoulder by a screw plunger (^\" "Whitworth thread), 

 which is also perforated axially by a hole 1-7 mm. diameter. This plunger is 

 fitted with a milled head, about 2 cm. diameter, which, for lightness' sake, is 

 made of vulcanite. Thus an emanation capillarj' may very easily be slipped 

 right through the chuck when the head is unscrewed, but, on screwing up the 

 latter, the rubber tube is compressed longitudinally, so that the central hole is 

 contracted, and the capillary firmly grip]Ded by the rubber. In fig. 3 the left- 

 hand chuck is shown in its "near" position, with the milled head screwed up, 

 while the right-hand chuck, seen in section, is in the "far" position, with the 

 head unscrewed to release the capillary, which is also shown. Other details, 

 such as the supports for the jet holder, and some of the gearing are omitted. 



The manipulation of the instrument is very simple. The fingers are locked 

 in the "near" position, the milled heads unscrewed, and the chucks pushed as 

 close together as possible. The emanation tube is then slipped in, a forceps being 



