SCIOPTICON MANUAL 



155 



a small chamber, as at c (Fig. 39), at the foot of a single 

 jet through which the mingled gas is projected upon 

 the lime. 



THE MIXED JET. 



The mixed jet is the only one of the Drummond 

 variety superior in effect to Nos. 1 and 2, and this we 

 adopt as the No. 3 of the triple blow- 

 pipe. 



The mixed jet tube, m (Fig. 39), takes 

 the place of both the tubes of No. 2, 

 covering both apertures at the junc- 

 tion, j. 



The oxygen gas forced up through 

 the central aperture o', in the nozzle, 

 instead of being taken direct to the 

 lime by the jet tube, as in Nos. 1 and 2, 

 is allowed first to mingle with the hydro- 

 gen forced in with equal pressure at 

 the side aperture. 



The relative quantity of each gas is 

 regulated by the stop-cocks till the best 

 effect is produced, which, in theory, is 

 when there are two volumes of pure 

 hydrogen to one of oxygen, or about 

 equal volumes if coal gas is used. 



2To. 3, Fiff. 39. 



DANGERS PECULIAR TO No. 8. 



Serious accidents in operating the mixed jet are mostly 

 occasioned by carelessly collecting or transferring one 

 kind of gas into a bag partly filled with another kind, 

 and then attempting to use it in connection with an 

 ignited jet. It is common to distinguish the bags by 

 the letters H and 0, and it is further recommended to 



