DECHERY'S AUTOMATIC CAUTERY. 123 



from that of Paquelin, and has the great advantage of being automatic 

 in action when once started, and of requiring no bellows. Every one has 

 probably seen the flaring, roaring lamps used in carrying on railway 

 works, large building operations, etc., at night ; the roaring noise and 

 the intense light, distinguish them from others. Dechery's cautery is 

 a modified reproduction of one of these. It may be divided into 

 reservoir (a a), vapour-chamber (b), and burner. The illustration 

 shows these, the essential portions of the interior being indicated by 

 dotted lines. 



To resist the considerable pressure at which it works, the 

 instrument is strongly made of nickelled brass. The reservoir is shut 

 off from the vaporising chamber by a conical valve, worked by means 

 of a long spindle (c) carrying at its extreme end a milled nut. The 

 vaporising chamber consists of a small 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. 130), this 

 minute stream of high-pressure benzol vapour then rashes 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 mto 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 vaporismg 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 combustion being conducted to the vapour- 

 chamber and the stem to a sufficient degree to promptly convert the 



