INTRODUCTION. XI 



It is mounted in wood plated with metal, which protects 

 and holds the parts firmly in convenient position. 



The lime is in the form of a wheel, two and a half inches 

 in diameter, and five-eighths of an inch thick, giving an 

 available surface on its edge, five-eighths of an inch wide, 

 and about eight inches in length. 



Tt lies loosely in its holder or cradle, with its projecting 

 edge presented vertically to the blow-pipe, which, without 

 intercepting the light toward the condenser, inclines back- 

 ward more than is shown in the diagram, and impinges the 

 gas just below the middle of the front, at about an angle of 

 forty-five degrees, so the heat glances toward the open top, 

 while the light is intercepted in that direction by the upper 

 part of the lime wheel itself. Turning the lime wheel at its 

 projecting back edge a quarter of an inch or so (by the thumb 

 and finger, it being a non-conductor of the heat on its front 

 edge), brings down to the jet a fresh but hot surface, which 

 is kept to its fixed distance by resting against the front of 

 its holder. 



The flat mouth of the jet secures to a fuller flow of gas 

 the proportional efficiency of a smaller opening, and more- 

 over, favors the mingling of the gases outside as effectually 

 as it is done in the mixed jet, or nearly so. 



The mixed jet No. 3 now resembles No. 2 in appearance, 

 and is tipped with a carefully selected gun nipple, extra 

 ones being forwarded with the apparatus in case any 

 accident befalls the first. 



The elongated and curved top of the lime-holder socket 

 serves as a rest for the lime cradle, as a guide to its stem, 

 and as a shield from the alcohol wick. 



The height of the alcohol in the wick tube is little 

 affected by tilting the lantern, because the fountain rests 

 abreast of it. 



The three burners are interchangable, giving to this one 



