An act of the British legislature has been passed, according to which all gas-meters must lie so constructed as not to register more than 2 per cent in favor of the seller, and 3 per cent ill favor of the purchaser of gas; thus allowing 5 per cent for variation caused by the depression of the water-line on wet gasmeters. All meters fixed since the act came into operation must bear the seal of an inspector appointed th•act.
The dry gas-meter possesses advantages, which, were it in other respects equally reliable with the wet meter, would give it the preference. Once adjusted, it gives no further trouble; it is not liable to derangement in frosty weather; and, in passing through it, the gas takes up no additional moisture to increase the risk of annoyance from deposit of water in the pipes. But doubts are still entertained• by many of the durability of the machine (moan efficient and correct measure. The meter consists of chambers 'separated from each other by partitions; generally there are two, but some makers use three chambers. Each chamber is divided into two parts by a flexible par tition which moves backwardo and forwards, its motion being regulated by valves beau tifully contrived for the purpose. The meter bears sonic resemblance to a double or triple steam-engine. Following out this resemblance, Mr. Croll thus describes his meter: "It consists of a cylinder, divided, by a plate in the center, into two separate cylindrical compartments, which are closed at the opposite ends by metal disks; these metal disks serve the purpose of pistons, and they are kept in their places by a kind of universal-joint adapted to each; the space through which the disks move, and, conse quently, the means of measurement, is governed by metal arms and rods, which space, when Mice adjusted, cannot vary. To avoid the friction attending a.piston working in a cylinder, a band of leather is attached, which acts as a hinge, and folds with the motion of the disk; this band is not instrumental in the measuring, so that if it contract or expand, the registeriiig of the meter would not lie affected, inasmuch as it would 'only decrease or increase the capacity of the hinge, the disk still being at liberty to move through the required space; the leather is also distributed in such a manner, being curved, and bending 'only in one direction, that it prevents any wrinkles or creases fotming, and renders it therefore much more durable. The arrangement of the valves and arms are somewhat different to that of a steam-engine, although similar in principle." Consumers of gas should bear in mind, that the purpose of the meter is to inform them how much gas they are expending; and that while the seller of gas cannot visit it but at long intervals, the purchaser may from day to day, if he pleases, ascertain the quantity which has passed through the meter, and so detect irregularity or waste, which, if allowed to go on, would no doubt be put clown to error on the part of the seller of gas.
burner made on the argand principle is still the best when fully used, but it is expensive, somewhat troublesome to keep clean, and involves out lay for glasses from time to time. Jets and batwings have, consequently, almost sup planted it. These burners are now made by machinery at very low prices, so that to change them when out of order costs little, s easily done. They are also very easily cleaned. Jets are of two kiads—cockspu•s and union-jets. The cockspurs are pierced with one or more straight holes; the union-jets are pierced with two holes diverging inwards from the point of issue, so that two small streams of gas impinge on each other, and produce a flat flame. Batwings are made with a clean slit across the head of the burner. The union-jet is by far the most common. Metal burners are very liable to rust and become This difficulty is obviated in the patent burner made of a siliceous composition, which lasts for years without deterioration.
There is one important fact in the burning of gas, which is equally true of animal and vegetable oils. When a given quantity is burnt in a large flame, a greater amount of light is obtained than wh•the same quantity is burnt in a smaller flame. Hence one large lamp or gas-jet is better than three or four burning the same quantity in the same time. The cause of this becomes apparent by considering what takes place when it jet of gas is turned down to the lowest point. Here the white light altogether disappears, and only a blue flame remains; the small body of gas as it issues becomes mixed and diluted with air, and the whole is perfectly consumed, as in the Bunsen burner, without any of the carbon becoming solid and incandescent. On gradually admitting more gas, a white speck first appears in the middle of the blue, and this speck—the area of imper fect combustion—goes on increasing not only in absolute size, but its proportion to the area of perfect combustion becomes greater as the whole flame is enlarged. The limit to this economy is the quantity that can be burnt without smoke. This difference between large of i There are many contrivances for improved burners and improved modes of using gas. Among them are the suulights, introduced by the late Mr. of Liverpool. These consist of a ring of union-jets, placed horizontally and set round the interior of the base of a cone which is passed through the ceiling, and conveys away the products of combustion through a flue, thus serving, both for lighting and ventilation.