1000 An apparatus capable of supplying an equal quan tity of light by moans of oil gas, would in point of expence amount to nearly as follows Retorts with all their apparatus, condensing and washing vessels, and buildings for the same, . . • L.3,700 Gasometers, &c. of half the capacity of the former,• . 3,500 Main pipes, &c. the length supposed the same as before, but the capacity reduced one half, . . 7,700 Total, L. 14,900 The quantity of gas daily consumed will average 12,500 cubic feet, or half the bulk which could be required of coal gas.
Annual expenditure, L. 7,830 In the above calculation for the expence of coal gas, no mention is made of the coke, tar, ail, and am. monis produced. The value of the coke depende much upon the nature of the coal employed ; that obtained from such as the Newcastle coal answers well for house fires, drying kilns, stoves, &c.; but the Cannel coal, which used for making gas to a great extent in many parts of the kingdom, gives a very inferior coke, of frequently not more than to the value of the coal which produced it. The tar, when boiled and mixed with drying oil and other substances, forms a paint which may be used for common purposes ; it may also be converted into pitch, and by burning it in close vessels, a species of lamp-black is produced. On the whole, this and the other liquid products have, however, not been considered as of much value, and the getting rid of them and of the refuse lime, which has been used in purifying the gas, is often attended with an expence which their own value, and that of the charcoal, will not mo re than compensate.
Though the expence of lighting by gas from oil appears, on a large scale, not to be much less than double that of coal gas, the same great dispropor tion will not altogether hold for very limited quan tities of light, where the charge for an attendant forms a considerable part of the current expenditure.
A coal gas apparatus, however small, will, when in work, require the almost constant attendance of a person to manage the fire, to charge and discharge the retort, to renew the lime or other substance used for purification, and to remove that which has done its office, also to empty the tar reservoir, &c. In the other apparatus, when the oil reservoir is filled and once set to work, it requires no other at. tendance for a number of hours, than the keeping. of the fire in order ; and the production of gas can be continued at pleasure, or stopped by the mere turning of a cock, and the nuisances accompanying the formation and removal of tar, amtnoniacal liquor, and lime refuse, are entirely avoided.
An argand oil lamp with a burner three-fourths of an inch diameter, we have found to consume 406 grains of the best oil in one hour, when giving the light of 31 candles of the size above spe cified. Five thousand grains of oil will, therefore, give the same quantity of light that 1 lb. of tallow does, and valuing it at 5s. 6d. per gallon, the cost will be, with an allowance for wicks and trouble of trimming, about 61d.
The comparative expence of light from the differ ent substances mentioned below will, then be as fol lows : • s. Valuing the quantity which 1-1b. of tallow gives in candles at 1 0 An equal quantity of light from spermaceti, oil consumed in an argand lamp will be 0 61 A ditto ditto from whale oil gas,. 0 41 A ditto ditto from coal gas,. .. . 0 2i Or about 41-d-for a light-equal to what 1 lb. of tal low would give; and if interest on capital is includ ed, it will amount to about 4d. being, compared with the cost of coal gas-light, nearly as ten to six.
It would have been desirable to have been able to give a comparative table of the actual charges made for supplying gas-lights in the prin. cipal towns of the kingdom ; but unless. some stand.
and size of the burner or burners employed was fixed, any thing of this kind would be nearly impracticable. In some places the Argand burners used are of three or four different sorts, and named No. 1, No. 2, &c. the smallest being distinguished by the least number ; the reverse occurs in other places, where the highest number is used to desig.
nate the least. The number and size of the per forations vary considerably; as likewise does the length to which the flames are allowed to be burnt; and variations also take place from time to time in some towns lighted by gas, which circumstance alone would render any attempt at a comparison of the rates charged of doubtful utility.