The use of these appliances is very important. Planted at convenient and commanding spots,--often at the corners of streets or roadways, and at varying distances apart, ranging from fifty to about four hundred feet, according to the circumstances of the locality, and marked also, not only by the plate in the pavement, but by the letter H, placed in a conspicuous position near,--the fireman can now, at almost a moment's notice, find the hydrant, and obtain an ample supply of water for his engine, or even a jet of water for the fire, before an engine is on the spot. Very different from the troublesome and hindering work of floundering about, possibly in fog or rain or snow, to find the fire-plug, and then to find the turncock which governed the plug. On snowy or foggy nights, the difficulty and delay were sometimes very great; and the substitution of an extensive system of hydrants, with their quickly-obtained water-jets for the old fire-plugs, may rank as one of the most efficient means of fire extinction in the closing years of the nineteenth century. Firemen being thus interested in the pressure of water in the mains, an apparatus for recording the pressure automatically was fixed up at the fire-brigade headquarters at Southwark Bridge Road in November, 1898. A clock stands at the top of the instrument, and under the clock is a roll of paper, having the hours of day and night marked upon it, and divided into sections. A small pipe connected with the main runs under the big engine-room, and acts upon mechanism beneath the paper roll, and the clock and the column of water, and its pressure per inch, are marked in red ink upon the sheet, varying perhaps from forty up to seventy-five or even eighty pounds per square inch. At noon each day the sheet can be removed, and forms a permanent record of the variation in water pressure in the mains of the neighbourhood. But if the number of hydrants is large, the area to be protected by the brigade is also very large. Including the ancient city of London, which is estimated to cover about a square mile, the area measures about 118 square miles. Of these, twelve are estimated by the fire-brigade committee to be covered by parks and open spaces, where fire-hydrants will probably never be needed. This leaves, however, a net area of 106 square miles, extending from Sydenham to Highgate, and from Plumstead to Roehampton, to be efficiently protected by the brigade. Another means of water supply has been suggested. In his evidence at the Cripplegate Fire Enquiry, Mr. John F. Dane, an ex-officer of the Metropolitan Fire-Brigade, suggested that at the centre of the junction of the most important streets surrounded by large buildings underground tanks should be placed, and supplied by the main water-pipes. The tanks would be empty until required, and would be under the control of the brigade, while the hydrants should still be maintained for service. Such tanks were in use at Leeds and at Salford.