Each burner develops 300 candle-power. A double-cylinder steam-engine working a double pump supplies 300 of these burners, giving a total lighting-power of 90,000 candles. As compared with the cost of low-pressure incandescent lighting the high-pressure system is very economical, being but half as expensive for the same amount of light. It is largely used in factories and railway stations. It may be seen on the Tower Bridge, Blackfriars Bridge, Euston Station, and in the terminus of the Great Central Railway, St. John’s Wood. Perhaps the most formidable rival to the electric arc-lamp for the lighting of large spaces and buildings is the Kitson Oil Lamp, now so largely used in America and this country. The lamp is usually placed on the top of an iron post similar to an ordinary gas-light standard. At the bottom of the post is a chamber containing a steel reservoir capable of holding from five to forty gallons of petroleum. Above the oil is an air-space into which air has been forced at a pressure of fifty lbs. to the square inch, to act as an elastic cushion to press the oil into the burners. The oil passes upwards through an extremely fine tube scarcely thicker than electric incandescent wires to a pair of cross tubes above the burners. The top one of these acts as a filter to arrest any foreign matter that finds its way into the oil; the lower one, in diameter about the size of a lead-pencil and eight inches long, is immediately above the mantles, the heat from which vaporises the small quantity of oil in the tube. The oil-gas then passes through a tiny hole no larger than a needle-point into an open mixing-tube where sufficient air is drawn in for supporting combustion. The mixture then travels down to the mantle, inside which it burns. An ingenious device has lately been added to the system for facilitating the lighting of the lamp. At the base of the lamp-post a small hermetically-closed can containing petroleum ether is placed, and connected by very fine copper-tubing with a burner under the vaporising tube. When the lamp is to be lit a small rubber bulb is squeezed, forcing a quantity of the ether vapour into the burner, where it is ignited by a platinum wire rendered incandescent by a current passing from a small accumulator also placed in the lamp-post. The burner rapidly heats the vaporising tube, and in a few moments oil-gas is passing into the mantles, where it is ignited by the burner. So economical is the system that a light of 1000 candle-power is produced by the combustion of about half-a-pint of petroleum per hour! Comparisons are proverbially odious, but in many cases very instructive. Professor V. B. Lewes thus tabulates the results of experiments with various illuminants:-- _Cost of 1000 candles per hour._