of counterpoise weights, to give 3 inches pressure, mark the scale or intended scale of the gasholder at a point opposite the index, and if the gasholder bell remains in the same position for five minutes the connections are sound. Put the bell of the gasholder in perfect balance by replacing the counterpoise weights which have been removed; then open C and allow the water from A to descend into E; listen for the time when it ceases to run, then note the clock and wait five minutes to allow for drainage of the upper vessel, then close C. With F closed and a vent cock (not shown in the woodcut) open, draw off the water from G and return it to A with sufficient in addition to cause the level to be above the neck of A, draw off the excess by the side cock, strike the water with the glass across the neck as before, open F and C, and so proceed until the gasholder scale is formed: marks, as in the former illustrations, being made after each delivery of air into the bell.

10. These various methods of using water are, as will be readily realized, both slow and exceedingly laborious, for more than 62 lbs. of water had to be weighed, measured and lifted for every cubic foot of air measured; and it will be hereinafter shown how much more facile and rapid the methods are, which have been practised since the year 1861.

THE SALES OF GAS ACT.

11. In the year 1859 an Act was passed entitled "An Act for Regulating Measures used in Sales of Gas." This Act was modified by two subsequent Acts, which deferred the date at which it was to come into operation, changed some of the authorities who were to carry its provisions into execution, and finally rendered its application permissive instead of compulsory -dependent, in fact, upon the resolutions of magistrates and

other local authorities. As a consequence of the last alteration, many of the authorities neglected to adopt the Act from considerations, it may be, of the attendant expences. Nevertheless the Act is virtually in operation all over the kingdom, for very few meters are put into use without having been previously verified and stamped by a Public Inspector.

12. In the original Act it is enacted that—

CLAUSE II. After the passing of this Act, the only legal Standard or Unit of Measure for the Sale of Gas by Meter shall be the Cubic Foot, containing 62.321 Pounds, Avoirdupois Weight, of Distilled or Rain Water weighed in Air at the Temperature of Sixty-two Degrees of Fahrenheit's Thermometer, the Barometer being at Thirty Inches, except as relates to Contracts made before the passing of this Act by which a different Unit of Measure is adopted, which Contracts may not be renewed. CLAUSE III. Within Three Months next after the passing of this Act, Models of Gasholders measuring the said Cubic Foot, and such Multiples and Decimal Parts of the said Cubic Foot as the Lord High Treasurer or the Commissioners of Her Majesty's Treasury of the United Kingdom for the Time being shall judge expedient, and, from Time to Time after the Expiration of the aforesaid Period of Three Months, Models of such further Multiples and Decimal parts of the said Cubic Foot as the Lord High Treasurer or the said Commissioners shall from Time to Time think expedient, shall be carefully made, with proper Balances, Indices, and Apparatus, for testing the Measurement and Registration of Meters, and such Models shall be verified under the direction of the Lord High Treasurer or the said Commissioners, and when so made and verified shall be deposited in the Office of the Comptroller General of the Exchequer at

Westminster; and copies of the Models so from Time to Time deposited, verified as aforesaid, shall be sent to the Lord Mayor of London, and the Chief Magistrate of Edinburgh and Dublin, and to the Chief Magistrate of such other Cities and Boroughs and to such other places and Persons in Her Majesty's Dominions as the said Lord High Treasurer or the aforesaid Commissioners may from Time to Time direct; and the said Lord High Treasurer or the said Commissioners shall appoint a competent Person or Persons to design and make, subject to the Approval and by Direction of such Lord High Treasurer or the said Commissioners, Stamps of a uniform Design to be used for stamping Meters throughout the United Kingdom, with only such Variations of Numbers or Marks thereon as shall be sufficient to distinguish each Inspector's District.

13. The clauses which follow the foregoing relate to the appointment of meter inspectors, the models, or copies, of the standard measures to be used in testing meters, the verification of meters, fees for such verification, &c., &c.

14. In accordance with the provisions of the third clause, the following standard of cubic capacity were accordingly constructed under the direction of the Astronomer Royal, namely, a measure of such capacity as to contain 62.321 lbs. of distilled water at the temperature of 62° Faht., and with the barometer at 30 inches (which measure is usually called the cubic foot bottle), and three gasholders of the respective capacity of one and one-tenth, five and five-tenths and eleven cubic feet. In 1871 the Royal Commissioners of Weights and Measures increased the number of gas measures by including GAS METERS of a very perfect character as secondary standards (24).

STANDARD GAS MEASURES,

15. THE CUBIC FOOT MEASURE, or unit.
GASHOLDERS, containing more than a cubic foot.
GAS METERS of special construction.

16. THE CUBIC FOOT MEASURE, or Bottle, as it is usually
called. This is shown in fig. 4, and is an outcome
of Mr. Alfred King's Transferrer, shown in fig. 3,
for the form of the bottle is practically identical
with that of chamber A of his transferrer; and to
that gentleman the credit is due of having been
the suggestor of a form of vessel so well suited for
the purpose, and which is so little liable to have
its form and therefore capacity altered by mode-
rately rough usage.

are very

FIG. 4. 17. GASHOLDERS.-The Government Standards elaborately finished and beautiful instruments, far too costly for general use. In principle of construction, they are identical with those employed by Public Inspectors and others for the verification of gas meters in this country, in the colonies, and abroad. By these standards, the working or "Inspection Standards," as they are called, are verified, and the divergence, or error in the latter, must not now exceed a quarter of a per cent., only one half the error formerly allowed, but which is nevertheless amply sufficient. The description which follows applies specially to "Inspection Standards," and generally to the Government Standards.

18. An instrument of this kind, fig. 5, consists like an ordinary gasholder, of a water tank and a cylindrical bell or holder fitting into the tank. The holder is free to rise to a certain height, and is made to contain a specific volume of air or