CHAPTER IV. 



LIME-LIGHT JETS, BAGS, PRESSURE BOARDS, ETC. 



HEBE are three forms of jets for the lime-light, 

 namely, the oxy calcium, the blow-through, or 

 safety form, and the mixed jet. The simplest 

 of all is the first named. 



The oxy calcium jet consists of a spirit-lamp, which is 

 fed from a little reservoir at the back of the lantern. The 

 spirit furnishes the necessary hydrogen, and through its 

 flame a jet of oxygen is passed, and impinges upon a 

 cylinder of lime placed just at the other side of the wick. 

 This lamp will well illuminate a disc of about ten feet in 

 diameter with a clear, white light. It has the advantage 

 of simplicity, but presents one difficulty in the circum- 

 stance that the lantern must be kept perfectly level. If it 

 is inclined backwards, the spirit cannot flow to the point of 

 combustion, and if it -is inclined forwards the fluid may 

 flow too rapidly towards the wick. In some forms of 

 oxycalcium lamp this is obviated by a special construction 

 of the spirit cistern, which is furnished with an automatic 

 valve for governing the supply of fluid to the wick. The 

 wick will rapidly become charred if the stream of oxygen 



