LANTERNS AND THEIR MANIPULATION 107 



FIG. 60. Star Dissolving Tap 



screen, but the turning on of the oxygen brings out the light 

 in all its brilliancy. 



All kinds of jets with two gas or vapour tubes are worked 

 with a dissolving tap, which in this case must be a 'six- 

 way ' tap, as two gases, or their equivalents, are supplied 

 to each lantern in turn. This is the form practically known 

 as a dissolving tap, 

 and was first invented 

 by the late Mr. Dan- 

 cer, of Manchester. 

 It is now made in two 

 principal patterns, one 

 of which, the ' star ' 

 tap shown in fig. 60, 

 was simplified out of 

 Mr. Dancer's model 

 by Mr. Maiden. In 

 this tap the supply- 

 tubes are stretched over the horizontal nozzles on each side, 

 and each side of the plug has a channel cut in it which 

 just reaches to the apertures over and under on each side, 

 leading to the two jets. Thus when the lever is half-way 

 both lanterns are ' on,' but any movement to either side cuts 

 off one jet. If both gases, however, were cut off altogether, 

 the jet would be put quite out ; and to avoid this there is a 

 small tube with a stop-cock in it, connecting the two jet-noz- 

 zles on the hydrogen side. The effect of this is to allow a 

 small quantity of hydrogen (adjusted by the small stop -cock) 

 to pass from the ' on ' nozzle, to the nozzle which is cut off, 

 so as to keep a small gas-flame, quite invisible as regards the 

 screen, alight in the cut-off lantern. Such a subsidiary stop- 

 cock is called a ' bye-pass.' To avoid any ' snapping ' when 

 a lantern is turned on, there is often a bye-pass made in this 

 dissolver for the oxygen supply also, and the diagram shows 

 both. An oxygen bye-pass must be very little indeed, so ae 



