ill OPTICAL PROJECTION 



worked in the middle of a room, it is very important to re- 

 serve enough space for the gas-bags or cylinders comfortably, 

 and to have this space protected by making a kind of fence 

 with some of the seats, within which no one is allowed to 

 come. If it is a juvenile audience, it is important to get some 

 elder lad appointed to act as sentinel over this. 



The connections are made as in the diagram, which shows 

 a star-tap (as the most puzzling). The hydrogen is connected 



from the bag or cylinder to the 

 nozzle across which the bye-pass 

 is fitted, if only one ; otherwise 

 to the one known to have the 

 longest channel. (If the jets 

 both persist in snapping out, 

 with a tap that has two bye- 

 passes, it is probable the gases 

 are taken to the wrong nozzles 

 supplying the dissolver, and that, 

 from the unequal length of chan- 

 nel, the hydrogen cuts off before 

 the oxygen). In the diagram, 

 the hydrogen goes to the left, 

 the oxygen to the right-hand 

 nozzle. The tubes carrying from 

 the dissolver to the jets may be 

 connected to either top or bottom 

 lantern, as regards one of the 



gases, provided the other gas be connected to correspond. In 

 the diagram the top hydrogen nozzle goes to the top jet, and 

 therefore the bottom oxygen nozzle must connect to the same 

 jet. With the other form of dissolver (fig. 61) both nozzles 

 on the same side go to the same jet, and the cylinders or bags 

 connect with the centre pair, and no mistake can be made by 

 a person of ordinary sense. 



The lantern lenses will now be wiped over if necessary, 



FlG. 63. Connections 



