In this country, from causes which would occupy too much space to review, gas-lighting has been confined to comparatively large. cities ; but at the present time, we are happy to say, that efforts are being made to introduce it into every locality. In the SCIENTIFIC AaiuuiCAN of March 7, 1857, we devoted considerable space to the illustration and description of gas-works adapted to small towns and villages, taken from an English publication; and public interest seems now to be awakened to the want of such works in every community. But more of fcliis anon. Let us continue our history. The greatest objection to the use of coal gas, at this period of its history, was the large proportion of sulphurated hydrogen which it contained—a very noxious gaseous compound, which by burning is transformed into acrid vapors, eminently detrimental to life, furniture, plate, silk hangings, paintings, &c. Clegg introduced the purifying process, by passing the gas through lime-water, and subsequently through dry powdered lime. Nevertheless, it required a long time before the purifying was sufficiently perfected or attended to by companies to overcome the objections to the use of.coalgas. Indeed, to the present time, many wealthy owners of costly picture galleries in England, many silk manufacturers and silversmiths, cannot be persuaded to introduce it into their houses or factories. In consequence, the efforts of gas engineers in Europe have been lately almost entirely confined to the improvement of the purifying process. The difficulty is, in that branch of manufacture, as in most others, to combine efficiency with economy and simplicity. The simplest test by which consumers can ascertain the comparative purity of their gas in this respect, is by holding above a gas-burner, a piece of paper dipped in a solution of acetate of lead (sugar of lead). If the gas is not pure, the paper will turn to a greyish, and even a black tint; whilst pure gas will leave it white. The bad quality of coal gas at its origin induced the formation of rival companies, who used oils, fats, rosin, and other materials free from sulphur. Though the price of oil gas was four times higher than that of coal gas, many preferred it on account of its purity. But the rudeness of the processes employed in the distillation of oil or rosin, and the varying cost of these articles in England, as compared with that of bituminous coals, combined with the improvements in the manufacture of coal gas, soon put an I end to all competition, and coal is now the article most generally used there. In several parts of Europe other materials arc yet distilled for illumination. In some cities, the fat withdrawn from the washings of wool, in the manufacture of cloth, is used to make gas; in others, rosin gas is yet manufactured. In some parts of Germany, the wood gas process has been sufficiently perfected to make it preferable there to coal gas ; and we have no doubt that the discoveries of Dr. Pettenkoffer, of Munich, will make the use of wood gas much more general than it has hitherto been. The most important device, however, in gas-lighting (due also to Mr. Clegg's ingenuity) is the meter, by which gas is measured to consumers. That instrument has been the means of decreasing the price of gas, by making every one pay for what he burns. Before its introduction, gas was sold by approximation, based on the number of burners used in each house. This, of course, gave rise to great frauds, which weighed heavily on the honest customers. When wall constructed, the meter is a fair reckoner, though frequent differences arise on this subject between gas companies and their customers. Tn"e fact is, that the discrepancies occurring between one period of consumption and another, which are always attributed to the meter, come more likely from differences in the quality of the gas furnished; for it is a fact not sufficiently known, that the poorer iHie gas, the faster it will flow through the burners; and, though the meter has registered correctly the volume of gas delivered, it does not follow that the consumer has received ah equivalent amount of light. A desirable improvement in this direction would be a meter registering the time or duration of light, rather than the volume of gas. Until that is accomplished, gas companies have no inducement .to furnish good gas. The worst article with which consumers can be satisfied will be more likely to be manufactured, since it is the cheapest to produce, and the dearest to sell. A complete review "of the different improvements introduced in the manufacture of gas would occupy too much space, and more properly belongs to special works on the subject. As the process is now generally practiced, it consists in placing from 1 to 3, 5 and even 12 retorts in an oven heated by a fire fed with a portion of the coke left from tho distillation of gas coal. These retorts are long cast iron or clay tubes, usually of the sectional shape of a D, open at one end, and closed by means of a plate luted with soft clay. It is furnished with a pipe, through which the gas, as it is generated, passes off to the condensers, purifiers, and gas-holder. The retorts are kept at a cherry red heat; a charge of coal is shoveled in, and the retort closed. The gas and vapors contained in the coal soon begin to be evolved, and continue to distill until nothing but dry coke remains in the retorts. The richest gas is generated in the first three hours; and it requires from four to eight hours to exhaust the coal. In the best managed gas-works the charges are renewed every four hours, the quantity and quality of gas varying with almost every kind of coal used. Cannel coal gives the richest ga3, and in larger quantities ; but as it leaves but little coke, it would not be economical to use it alone. A mixture of Cannel with caking coal, in certain proportions, afford the best results; but the reduction of the quantity of Cannel coal below a certain standard is soon perceivable, by a diminution in the illuminating power of the gas flame., and an increase in the bills of the customers. On an average, a tun of mixed good gas coals produces 8,000 to 10,000 cubic feet of gas, (or from four to five feet per pound,) 1,200 pounds of coke, 200 to 300 pounds of tar, and 200 to 300 pounds of ammoniacal water. One pound of rosin gives, in the old rosin apparatus, from six to nine feet of gas, the illuminating power of which is greater than that of ordinary coal gas as 5 to 3, and sometimes as 6 to 3. One gallon of fish oil gives from 70 to 90 feet of gas, of double the value of coal gas. But, on account of its cost everywhere, oil is now but little used. Some wood gas-works have been tried in this country, but from some unknown causes, have riot been so extensively built as we think that their merit deserves, although the original introducers (Messrs. Breisach) have still a patent on the process. The objection stated is, that the difficulty of obtaining tho right kind of wood sufficiently dry, and of purifying the gas of a large proportion of carbonic acid, renders the process too uncertain and costly for large practical operations. These difficulties have been overcome, and there are many places where wood gas would be cheaper than coal. The best results seem to have been obtained at Philadelphia, Pa'., where a cellular retort is employed, in which the volatile matters evolved from the wood are made to circulate in heated chambers placed under the retort, and by which they are mostly decomposed into permanent gas, which is afterwards passed through lime obtained from oyster shells. The wood is previously baked for that purpose. It is stated that 12,000 to 15,000 feet are obtained from a cord of south yellow pine or dry oak. In a report of the analysis of the Philadelphia wood gas by Professor Gibbs, it is stated that its illuminating power is superior to coal gas. However, at the present prices of the other material, and in the actual state of tho manufacturing process, it does not seem advisable to use wood where coal is cheap and obtainable. Within a few late years, a number of small gas-works have been erected in or near gentle-mens' private houses in the country, in which gas is generated from rosin oil, poured in small streams into retorts placed in a stove. They answer very good purposes where convenience is of greater import than economy ; but the cost of rosin oil prevents its competing on a large scale with coal or wood. Several patents on portable rosin oil works have been taken out of late in this county. A question very often raised here is, why gas costs so much more in this country than in England. Several causes can be assigned for it. First, gas coals cost more here than there, and the cheapness of anthracite coal renders coke of less relative value than it is in Europe ; wages, and the value of capital, are higher; the residuary products are more easily disposed of there than here; tar is distilled for its naphtha and pitch; ammonia is made into sulphate and muriate of ammonia. The first is sold as manure; the last is used in the arts; the lime is also readily disposed of for more than its original cost. In America, gas companies have to rely more particularly upon the sale of gas for their income; as for the other products there is not so great a demand. Our cities cover a much greater area than those of the same population in Europe, therefore the outlay for main is much greater. However cheaply gas can be made from coal, when the cost of materials alone is taken into account, many difficulties yet prevent its adoption in our small communities. The first establishment of the apparatus is complicated and costly. The distillation of coal must be continuous, as it sometimes takes several days to heat the retorts to the required temperature; therefore two laborers at least are required, with an engineer to conduct operations and attend to repairs, which are somewhat expensive, since the renewing of the retorts necessitates the rebuilding of benches, which costs nearly $100 per retort. It will be understood how the summer consumption of many localities would not justify such expense. Indeed, ire have heard of places where gas sold at five dollars, yet left a loss of one dollar per every thousand feet made in summer. From what precedes, we think that all improvements which tend to remove those difficulties deserve attention. We have been furnished with drawings, plans and views of gasworks, constructed under Mr. Aubin's patents, adapted to small towns, villages, and factories. They have been tested at Palmyra, Cohoes, Murphreesborough, Rondout, San Francisco, and other places ; and the statements which accompany them seem to confirm the claims of the inventor, who offers them as calculated to generate gas from any material, thus enabling each locality to adopt the cheapest, whether coal, rosm. oily seeds, sawdust, asphaltum, or mixtures of the same, and which can bo operated one hour, one day, or constantly, as required. In an early number WB shall publish illustrations of the Palmyra Gas-works, erected on this plan ; and from them our readers will be able to form a sufficient idea of their merits. We will add that patents have been obtained in France and England, through the Scientific American Agency, on Mr. Aubin's improvements.
This article was originally published with the title "Gas lighting—Article II"