1893.] A New Portable Miners Safety-lamp. 487 



hydrogen was fed through a copper tube of very fine bore within the 

 lamp to a jet terminating beside and just above the wick of the lamp. 

 This copper tube passed through the oil reservoir of the lamp. 



The hydrogen having been kindled by the lamp-flame, the wick was 

 drawn down by the " pricker " until the oil-flame was extinguished. 

 The hydrogen flame was then set to a standard height of 10 mm. by 

 regulating the very tapering cylinder- valve, whilst looking across a 

 vertical 10 nim. wire fixed on the wick-holder in front of the hydro- 

 gen flame. The flame-cap was then looked for against a dead-black 

 background, produced by smoking with a taper a vertical strip half an 

 inch wide upon the interior of the back of the lamp-glass. The lamp- 

 glass was specially made of greater length than usual, so as to enable 

 the whole of a flame-cap 60 mm. in height to be seen. The height of 

 any flame-cap thus observed was estimated by comparing it with the 

 standard 10 mm. hydrogen flame, or, if the flame had increased in 

 height, by taking the vertical wire as the fixed 10 mm. standard of 

 measurement. 



When the observation of the flame-cap had been completed, the 

 lamp-wick was pushed up once more against the hydrogen flame ; and 

 as soon as the oil-flame had been kindled, the hydrogen was shut off 

 by the valve of the cylinder, and the flexible tube was disconnected 

 from the lamp. 



The whole process of producing the standard hydrogen flame within 

 the ordinary safety -lamp was very simple and was very rapidly 

 effected ; and the change from the oil flame to the hydrogen flame, 

 and the converse, presented no difficulty. A little practice enabled 

 the operator to turn on the hydrogen sufficiently slowly, if the valve 

 was properly constructed ; and a little care sufficed to prevent the 

 extinction of the hydrogen flame by sudden shocks imparted to the 

 flexible connecting tube. 



This form of apparatus appears to be suitable for many purposes. 

 But practical mining men objected to the unnecessarily large weight 

 and dimensions of the hydrogen cylinder, and to the inconvenience of 

 the connecting tube. For making one's way along rough and awk- 

 ward passages underground something more compact and light was 

 requisite. 



After many experimental forms of apparatus had been tried, a little 

 steel cylinder directly and rigidly attachable to the safety-lamp was 

 adopted. It is shown attached to Ashwortii's modified lamp in fig. 1. 

 The sectional drawings represent the key of the valve below the 

 cylinder; it is in reality at the side and is detachable; the attach- 

 ment of the cylinder to the lamp is also not accurately represented 

 in the sections. This cylinder may be adapted to any other form of 

 safety-lamp, but for several reasons Ashworth's lamp has been pre- 



