lechery's automatic CAUTERY. 161 



brass casting, hollow in the centre, and presenting two apertures 

 — that at the bottom, through which the benzol enters, being 

 closed by the conical end of the spindle ; and a second, 

 extremely small one at the side, through which the vapour issues 

 at high pressure. As will be noted (see Fig. 216), this minute 

 stream of high-pressure benzol vapour then rushes through a 

 rather wide tube, inducing in its passage a smart current of 

 air, with which it becomes intimately mixed, and finally burns 

 in the head with a bright blue, smokeless, but intensely hot 

 flame. 



To start the apparatus the large bottom nut is unscrewed, and 

 the reservoir filled with carefully filtered benzol. (It is important 

 to filter the benzol carefully, as the smallest speck of foreign matter 

 may choke the minute orifice in the vaporising chamber from which 

 the vapour issues.) The parts are then screwed together, the valve 

 spindle turned home, and the head heated in a spirit-lamp flame for 

 two or three minutes. This warms the head and vaporising chamber, 

 and prepares the apparatus for starting. As, however, there is at 

 first no positive pressure within the apparatus, the benzoline would 

 not flow into the vaporising chamber, and it therefore becomes 

 necessary to heat the stem, so as to cause the benzoline to expand 

 and to flow out when the valve is opened. The flame is therefore 

 advanced a little, and allowed to play round the top of the stem 

 for a minute or two, when, on opening the valve by turning the milled 

 head with the fingers, a few drops of benzoline are injected into the 

 heated vaporising chamber, are converted into gas, rush out into 

 the head, become mixed with air, and burn into the outer part of 

 the head, as above described. If the apparatus has been sufficiently 

 warmed at the outset it now becomes self-acting, the heat of com- 

 bustion being conducted to the vapour-chamber and the stem to a 

 sufficient degree to promptly convert the benzol into gas as it issues 

 from the reservoir, and to keep the benzol in the reservoir itself 

 nearly at boiling-point. It may be imagined, however, that the 

 pressure in the apparatus would become dangerous and involve an 

 explosion. Two safeguards are provided against this. Firstly, the 

 apparatus is very strong ; and secondly, an undue pressure in it 

 would force benzoline outwards in such quantity as to produce large 

 white flames, and thus give timely notice of danger. In practice 

 the writer has found the apparatus remarkably steady and reliable. 

 The firing points and edges are easily heated to a bright cherry red, 

 and the apparatus works without any regulating for twenty minutes 

 to half an hour, when a turn of the milled head will enable one to 



