122 



OPERATIVE TECHNIQUE. 



allowed to flow away, leaving the sponge saturated. The parts 

 are then screwed together, the bellows affixed and started, the 

 little two-way stopcock (a) at the bottom turned nearly at right 



angles, the small screw (d) in the 

 head opened as far as possible, and 

 a light applied to the holes shown in 

 .2 the head. If all is acting properly, a 

 I strong bluish flame will be seen within 

 ^ the head, and a rather loud hissing 

 ■Z sound will be heard. If not, the bottom 

 ^ stopcock is turned one way or the 

 'i. other, so as to alter the proportions of 

 ^ air and benzoline vapour passing to 

 '4 the head, until the flame appears and 

 i burns steadilv. In a minute or two 

 ^ the entire head will become strongly 

 J heated, and if the top screw (in the 

 ■g head) be then turned home, the blue 

 ■^ flame will disappear, the hissing noise 

 Z will cease, and the point of the cautery, 

 .5 previously quite dull, will suddenly 

 .5 begin to glow, and soon attain a bright 

 ^ reddish-white heat. The reason of this 

 y is that the direct flame is extinguished, 

 ? and the vapours are caused to burn 



witliin tJie platimiiii point or head. The 

 ^ instrument is now ready for use, and 

 >^. will continue acting for twenty minutes 

 = to half an hour by simply workmg the 

 r; bellows. Should the heat decline, a 



1 slight turn of the lower stopcock will 

 I admit more benzoline vapour, and re- 

 '■^, store the required temperature. If 

 V; employed in the open air some pre- 

 's caution is required when starting to 



shield it from draughts. A point of 



considerable importance is to obtain 



the right kind of benzoline ; the 



F"^- 150. common benzoline sold in oil-shops 



for use in cabmen's lamps or in the little cheap night lamps seems 



to answer best. 



The second instrument shown (Fig. 150) is quite different in principle 



