12inch x 18inch Poster Although it was well known that the air of coal mines contained gas which caused explosions on coming into contact with naked lights, it was not until 1815 that a practical safety lamp was devised. Sir Humphrey Davy found that a tube of wire gauze so cools a flame atempting to pass, that in prevents the ignition of flammable gas on the other side, and this principle is embodied in the "Davy" lamp. - There is a border around the image. Image size is correct.