170 Ml"* Anderson on the Illiimmating Power (yf Coal-Gas. 
the number of lamps, of various kinds, to which these retorts 
are found to afford an abundant supply of gas, is 650, inclu- 
ding, however, nearly 100 which are only lighted on Sundays 
in churches. The lamps are of the following descriptions : 
1 Jet, 
52 
2 do. 
94 
3 do. 
80 
5 and 7 Cock spurs, 
7 
Batwings, 
22 
Argands, 10 holes, 
221 
Do. 14 do. 
125 
Do. 18 do. 
24 
Do. 22 do. 
26 
651 
From this statement it appears, that a single retort at the 
Perth Gas Manufactory, is capable of affording an ample sup- 
ply of gas to about SOO lamps, the greater number of which are 
Argands, and many of them batwings, burning upwards of 
twelve hours daily. This result, so very different from the 
number of burners supplied by a single retort in other places 
I ascribe to two causes : In the first place, to a more thorough 
decomposition of the coal, arising from the peculiar manner in 
which the retorts are set ; and, in the second place, to a more 
effectual separation of the tar and other noxious products than 
has hitherto been effected by the modes of purification usually 
employed. 
With regard to the gas itself, I shall avail myself of your in- 
dulgence to give the result of a considerable number of experi- 
ments, which I performed with a great deal of care, in order to 
determine its illuminating power, in reference to that of a’ Ken- 
sington candle of the description termed short sixes The 
1st column shews the kind of burner ; the 2d the number of 
cubic inches of gas consumed per hour ; the 3d the number of 
candles to which the light was equal, as determined by the me- 
thod of shadows ; and the 4th the number of inches per hour 
which corresponded to the light of one candle. 
* One retort supplies gas to about 100 burners in Edinburgh ; to 45 in Lon- 
don ; to 31 in Berwick, &c. 
