Hey, cabby! How much to take me to the station?
"Five bucks, sir."
"And how much for my suitcase?"
"No charge for the suitcase, sir."
"Okay. Take the case and I'll walk."
Safety lampIn 1816, Sir Humphry Davy's safety lamp was first used in a coal mine. Deadly explosions had been a continual hazard caused by the flammable gas, methane, leaking out of the coal seams ignited by the flame of a miner's lamp. There had been previous attempts by others to make a safety lantern. Davy applied a scientific approach to determine the suitable fineness of wire gauze placed around the flame which would avoid ignition of flammable gas outside. He determined that the holes in the gauze should be less than 1/22 inch in diameter, and that the wire itself should be between 1/40 to 1/60 inch thick. Since the flame changed colour in the presence of methane, it also served as a warning to the miner to take protective action.«[Image: Davy safety lamp, circa 1816.] |
