Garum

GARUM: a heavily salted and highly seasoned sauce or relish made from fish—prin cipally from those of the Scomber family, as the tunny, mackerel, etc.,—in the state of fermentation, the flesh itself or the blood and gills being variously employed. The Gramm of the Romans was generally prepared from the Anchovy (which see).

GAS.

The revolutionizing of general illumination by the substitution of gas for can dles and lamps, is credited to a Scotchman named William Murdock. He conceived the idea in 1792 and demonstrated its utility by illuminating his home at Redruth, Cornwall, with gas drawn through seventy feet of piping from the place of manufac ture. He also advertised his invention by carrying portable gas-lamps through the streets, the burners supplied by bladders filled with gas. This first product was poor in illuminating' power, smoky and unreliable, but Murdock made many improvements in it, including in his process its partial purification by passing it through water, whiCh is still one of the essential features of modern manufacture. The first illumi nation on a large scale was by a Murdock installation which lighted the Soho Engine Works at Birmingham, England, in 1798. The pioneer American gas plant was erected at Newport, R. I., in 1812, by David Melville. The first gas company formed to light the streets of an American city was that in Baltimore in 1816. Boston fol lowed in 1822 and New York in 1823.

The chief forms of commercial gas now utilized are coal gas, natural gas, water gas, producer gas, petroleum or oil gas and acetylene gas. Except where natural gas is obtainable, coal gas is the form chiefly employed for street and household illumina tion, household cooking, etc.

Coal Gas, also known as Illuminating Gas, is obtained by the Destructive Dis tillation (see sub-head in general article on DISTILLATION) of coal, principally bitu minous (or "soft") coal. When used chiefly for illuminating purposes, it is frequently enriched by the addition of petroleum gas or benzol, a coal-tar product. The rn crude product is most offensive in smell, but its odor is greatly modified and reduced by ing through a "scrubber"—falling water on a coke bed or perforated iron plates—by purification by oxide of lime or iron, etc.

The storage tank or cylinder of the gas plant, familiar in general appearance to every consumer, is essentially a large "bell" set inside a circular steel framework. The bottom of the bell rests in a deep-water seal and is automatically raised as the gas is carried into it. When the tank is raised close to the top of the framework, it is full of gas ; when it has shrunk low and the bare frame shows against the sky, the supply is very scant.

Commercial coal gas varies greatly in components but an average analysis win show about 46% hydrogen, 40% marsh gas (the principal constituent of natural gas), 5% olefiant gas or ethylene, which is extremely luminous, and 5% carbon monoxide.

It is the carbon monoxide which renders coal gas especially poisonous.

Natural Gas, which flows freely from subterranean sources in various parts of this, and other countries—generally from beds of coal or petroleum—varies considerably in composition, but marsh gas is its chief component. Pittsburg natural gas shows an average of 92% marsh gas and 3% olefiant.

Petroleum or Oil Gas is obtained by passing oil through superheated pipes or re torts. It can be made from any , fats, oils or grease—even from some city garbage.

Producer Gas, so-called because made in various types of "producer equipments" or machines, is made largely from low-grade coal, hard or soft. Instead of being secured, as coal gas, by dry distillation, it is obtained by the destruction of the coal by its own partial combustion in closed furnaces, steam being introduced during the process. It was formerly employed chiefly in the iron industry. It is not suitable for household purposes but in recent years has become increasingly important as power fuel.

Water Gas is manufactured from anthracite (or "hard") coal, or coke, and steam.. The coal is placed in an air-tight cylinder, ignited and blasted to incandescent heat. The blast is then shut off and dry steam is blown through, the resultant gas being carried by pipes into the reservoir. As soon as the coal begins to cool, the steam is shut off and the blast again blows the coal to a white heat, the process being repeated every few minutes until the coal is exhausted. Water gas is excellent for heating purposes, but where it is desired for illumination it is necessary to enrich it by the addition of carbon or petroleum gas.

Acetylene Gas is obtained by the action of water on calcium carbide. It gives a brilliant white light, but is too expensive for general use in competition with other commercial gases.

Store Illumination.

The retailer who relies on gas for store illumination, should use the best burners and mantles obtainable and see that both are always in good condition. With proper attention, a store lighted by gas can be made as brilliant as if wired for electricity.

The efficiency and cost of illumination is also affected by the color and coverings of the walls and ceiling. If painted white or even tinted a faint grey-cream, and kept clean and fresh, fully double the illumination will be obtained from the same number of burners as in places where the walls and ceilings are badly soiled or are covered with paper or paint of blue, green, brown or red. Next best to the faint grey-cream mentioned, are very light-greenish, and light yellow.