226 COMPOUND BLOWPIPE. 



furnished with an injecting syringe, for the introduction of the gases, 

 previously mingled in the proportions to form water ; it is furnished 

 also with an internal valvular apparatus of wire gauze, to guard against 

 explosions,* and with a tube of efflux mounted with a stop cock and a 

 platinum orifice. Great pressure may be a convenient means of bring- 

 ing more of the gases into the reservoir, but it is of no avail as regards 

 the heat, for not being at their efflux, adequately resisted by the air, it 

 amounts to nothing more than supplying the gases in sufficient quan- 

 tity. The previous accurate adjustment of the proportions, may at 

 first view seem to be a point of importance, but after a little experi- 

 ence, there is no practical difficulty in hitting this proportion, when 

 the gases come from different reservoirs ; the eye will easily perceive, 

 by the color and size of the flame, and the appearance of the focal 

 point, when the proper proportion is attained ; and the effects have 

 proved that there is no important difference in the power of the in- 

 struments. Mr. Brooke's blowpipe has the advantage in neatness and 

 convenience of size, but its contents being soon exhausted must be 

 frequently renewed. It is obvious that the security of Dr. Hare's 

 contrivance may be easily connected with that of Mr. Brooke, by 

 simply providing two condensing boxes of proper size, one for hy- 

 drogen and the other for oxygen, and connecting them in the manner 

 represented in the cut on page 225. On account, both of strength 

 and capacity, two globes of metal would be most convenient ; and 

 an instrument, like that in the figure above referred to, would unite 

 all the most important advantages of the different varieties of appara- 

 tus, hitherto constructed for this purpose, and be at the same time, 

 free from their inconveniences, and from the danger attending Mr. 

 Brooke's. 



6. The figure in the note below represents the form of the instru- 

 ment, at present, used by Dr. Hare. It is less simple than those that 

 have been described, but the inventor says, that he has found it 

 equally convenient in use, as the most simple form, " while its parts 

 are peculiarly susceptible of advantageous adjustment."! 



* On a principle which will be illustrated under the history of the safety lamp, in 

 the section on the carburetted hydrogen gases. 



t '* B is a brass ball, with a vertical perforation, terminating in a male screw above, 

 and in a female screw below. Another perforation, at right angles to this, causes 

 a communication with the tube, t, which enters the ball at right angles. A simi- 

 lar, but smaller brass ball, may be observed above, with perforations similar to those 

 in the larger ball, and a tube, in like manner, entering it laterally. This ball ter- 

 minates in a male screw below, as well as above. The thread of the lower screw is 

 curved to the left, while that of the screw of the larger ball, which enters the same 

 nut, n, is curved to (he right. Hence the same motion causes the male screws to ap- 

 proach, or recede from each olher, and thus determines the degree of compression 

 given to a cork which is placed between them, in the nut. At S, -above the ball, a 

 small screw may be observed, with a milled head. This is connected with a small 

 tube which passes through the cork in the nut, and reaches nearly to the external 

 orifice, o, from which the flame is represented as proceeding. This tube is for the 



