1864. | Feat. 347 
line once more. Another observation is now taken, and this is 
repeated for an indefinite number of times; the mean result being 
capable of any degree of accuracy according to the number of observa- 
tions from which it is deduced. It will be seen that the reservoir and 
mercury gauge constitute a gigantic air thermometer, and the method 
of registration is capable of giving the most minute variations of tem- 
perature. The amount of work done by the sudden expansion of the 
gas has a fixed value in thermometric degrees, and the tracings on the 
glass plate hold all the data required to give the exact numerical 
relation between the two. We will not follow our authors into the 
details of their calculations, but will state from the results of their 
investigation, that the number 476 formerly used must be changed for 
that of 433, which is near that given by the labours of M. Seguin and 
Mr. Joule. From the method of operating, and the large scale upon 
which the work has been conducted, there is every probability of this 
number being very near the truth. 
In our last Chronicles of Science we gave a short notice of a new 
gas-furnace by Mr. G. Gore, of Birmingham, The same principle has 
since been applied upon a much larger magnitude, and furnaces on a 
commercial scale are now in use at the electro-plate manufactory of 
Messrs. Elkington, Birmingham, and elsewhere. These larger furnaces, 
as at present constructed, are capable of melting about 400 ounces of 
silver, copper, gold, German-silver, or if desirable, even cast-iron. The 
amount of coal-gas consumed varying from 800 to 400 cubic feet per 
hour. 
With a consumption of 360 cubic feet per hour, the following 
results have been obtained :—266 ounces of sterling silver were per- 
fectly melted within 25 minutes from the period of lighting the gas in 
the cold furnace, and the metal was sufficiently hot to cast for rolling in 
20 more minutes. A second quantity of 266 ounces of the same metal 
was then introduced and was perfectly melted in 11 minutes, with a 
consumption of 66 cubic feet of gas, value 2d., the price of gas being 
2s. 8d. per 1,000 feet; in a further period of 15 minutes the metal 
was sufficiently hot to cast for rolling. A quantity (116 ounces) of 
German-silver was then introduced and melted in 15 minutes, and, 
after 28 minutes’ longer heating, various highly-figured articles were 
cast from it in a most perfect manner. In a subsequent operation 460 
ounces of silver were melted in about the same time, and with an 
expenditure of scarcely more gas than was required to melt 266 ounces. 
The smaller sizes of this furnace are much used by dentists, 
jewellers, analytical chemists, assayers, enamellers, and others, in con- 
sequence of their readily fusing silver, gold, copper, glass, and even 
cast-iron, without the aid of a bellows or lofty chimney, by simply 
lighting the gas ; and the crucible and its contents being at all times 
protected from the air and yet perfectly accessible for examination, 
stirring, removal, &e. The burners of the larger-sized furnaces are 
formed of a series of plates of cast-iron, and may be readily removed 
from the furnace and placed to heat a retort, mufile, reverberatory 
chamber, or other apparatus, where intense heat is required; it is 
