DURHAM AND NORTHUMBERLAND. 201

Davy’s lamps will surmount these difficultiesI am yet at a loss to ascertain ; for the wiregauze is necessarily of so fine a texture, thatthe least concussion or splinter of coal wouldpenetrate and liberate the flame. It maycertainly answer very well for experimentwhen held with the greatest care, and merelysuspended by the hand in a region of gas:but even this will not last long; and in prac-tical application the perpetual hard usage towhich it would be subjected requires to beconsidered in speaking of its merits.

The very circumstance of its being insulatedwith gauze renders the light feeble, and pre-vents the application of any sufficient externalsecurity ; and though the gas burns within,and sometimes expands the flame completelyover the inner surface, there are evils arisingfrom it which I fear will be found difficult toremedy.

In fifteen minutes after it is lighted, the heatbecomes so intolerable that there is no touch-ing it, a circumstance which must soon renderthe fine wire unfit for use. In half an hourthe small apertures in the wire-gauze becomenearly choked up with soot, condensation, &c.;and in one hour the whole becomes totallychoked up, except about half an inch at thebottom; and in two hours the light can