1 4 Sir Humphry Davy on the jire-damp of coal mines , and on 
by a rapid jet of gas I produced an explosion in the body of 
the lantern ; there was not even a current of air through the 
safety tubes at the moment, and the flame did not appear to 
reach above the lower aperture of the chimney ; and the ex- 
plosion merely threw out from it a gust of foul air. 
The second safety lantern that I have had made is upon the 
same principle as the first, except that instead of tubes, safety 
canals are used, which consist of close concentric hollow me- 
tallic cylinders of different diameters, and placed together so 
as to form circular canals of the diameter of from - 1 - to — of 
Ha 4-0 
an inch, and an inch and long, by which air is admitted in 
much larger quantities than by the small tubes. In this ar- 
rangement there is so free a circulation of air, that the chim- 
ney likewise may be furnished with safety canals. 
I have had lamps made for this kind of lantern which 
stand on the outside, and which may be supplied with oil and 
cotton without any necessity of opening the lantern; and in 
this case the chimney is soldered to the top, and the lamp is 
screwed into the bottom, and the wick rises above the air 
canals. 
I have likewise had glass lamps with a single wick, and 
argand lamps made on the same principle, the chimney 
being of glass covered with a metallic top containing the 
safety canals, and the air entering close to the flame through 
the circular canals. 
The third kind of safe lamp or lantern, and which is by far 
the most simple, is a close lamp or lantern into which the air 
is admitted, and from which it passes, through apertures 
covered with brass wire gau%e of ~o an i nc h thickness, 
the apertures of which should not be more than of an 
