He found the illuminating power of oil gas to coal gas as two to one in volume; and from an average of all the experiments made upon the two gases, taking them upon a fair average quality, found the proportion of the illuminating power of the two gases-two measures of coal gas to one of oil gas in volume. One cubic foot of atmospheric air, mixed with from ten to twenty-five feet of oil gas, would materially affect its illuminating power.

FINIS.

In correcting the press, the following errors have, unfortunately, escaped notice.

Page 82. For "RETORTS of Mr. Wilson," &c., read PATENTS,

&c.

163. In the note for "volatile and foots," read volatile oil

and foots.

416. After " London and," insert Westminster.

418. For "£15 and £29 per 1000 cubic feet," read 15s. and 29s.

PRINTED BY G, SMALLFIELD, HACKNEY,

"LET THERE BE LIGHT!" proclaimed the ALMIGHTY LORD. Astonished Chaos heard the potent word;

Through all his realms the kindling Ether runs,

And the mass starts into a million suns.

DARWIN.

LONDON:

ROWLAND HUNTER, 72, ST. PAUL'S CHURCHYARD.

1827.

THEC

G. SMALLFIELD, PRINTER, HACKNEY.

PREFACE.

THOUGH gas is now so extensively introduced and employed as the medium of obtaining light, comparatively few are well acquainted with the detail of its production and preparation for use; and hence, in many cases, a very imperfect estimate is formed of its important advantages. To supply this deficiency is the principal object of the following Compendium of Gas-lighting, which may be considered as an attempt to render the knowledge of its principles, apparatus, and processes so familiar, as to be easily understood.

The engraving which represents the apparatus for producing and purifying coal gas, is contrived to exhibit at one view the connexion of the different parts with each other; and, with the assistance of the description, it is hoped that the whole process is so plainly elucidated, that any person who may never have seen the operations will readily and perfectly understand them.-The engraving of the Patent Oil-gas Apparatus, exhibits a section of one of them in its most im

proved and complete form; and it is presumed, that its mode of action will be readily comprehended.

The Tell-tale, the Pressure Indicator, the Apparatus for Registering the Impurities of Gas, and the Instrument employed for ascertaining the Specific Gravity of Gas, are recent inventions, and constructed by Mr. Samuel Crosley. Heretofore, no descriptions of these useful and important additions to Gas Apparatus have been published; but, by the obliging permission of the inventor, the author has been allowed to communicate an account of their construction to the public. The detail of the apparatus and process of making gas from tar, is the substance of an original communication.

From the great utility of the Gas-Meter, no ordinary care has been betowed in describing its principle and mode of operating, so as to render both of them easy to be understood. The figure represents a section of one of the most effective and complete in its construction.

With a view of conveying clear and correct notions of the nature and properties of the gaseous bodies, to such as may not be acquainted with the terms or principles of chemistry, the Explanation of Chemical Terms, &c., has been subjoined. In this part, plainness and perspicuity have been invariably studied; and, to enable