Mr Anderson on the Illiimmatkig Power of Coal-Gas. 383 
nating power of coal-gas^ as it is manufactured at the Perth Gas- 
works, I stated that three retorts were found sufficient to pro- 
duce an adequate supply of gas to about 600 lamps, lighted 
during the usual time of burning in large towns. As I under- 
stand this result has been ascribed to some peculiarity in the 
coal used for carbonization, I think it right, in order to remove 
all mistakes on the subject, to mention that the coal used at the 
Perth Gas-works, is oPthe kind termed Cannel Coal, and as I am 
informed, greatly inferior in quality to the coal of the same des- 
cription, which is employed for the production of gas, both at 
Edinburgh and Glasgow. The retorts, which are set on se- 
parate furnaces, are charged every three hours, with about one 
hundred pounds of coal each ; so that the whole daily con- 
sumpt of the three retorts is about 2500 lb., or nearly 23 cwt. 
From this small quantity of coal, which, inclusive of fuel, costs 
about 18s. a-day, abundance of gas is produced to supply, at 
present, no fewer than 891 lamps, of the following kinds : 
Burners. 
Kumber. 
iVo. of Jets-, 
No. 1 Jets, 
67 
67 
2 do. 
134 
268 
3 do. 
74 
222 
5 do. 
2 
10 
7 do. 
2G 
182 
1 Argands 
10 holes, 
298 
2980 
2 do. 
14 do. 
136 
1904 
3 do. 
18 do. 
56 
1008 
4 do. 
22 do. 
37 
814 
.Batvvings, 
61 
732 
Total, 
891 
8187 
Many of these lamps burn to a late hour, and some of them 
the whole night ; but it is proper to add, that a few of them are 
lighted only on Sundays, and others now and then, in the course 
of the week. Still, however, if these occasional lights be reduced 
to equivalent ones, by making a suitable allowance for the time 
they are not used, it may be affirmed, that, three retorts at the 
Perth Gas-works furnish a sufficient supply of gas to about 800 
lamps of the kind above mentioned, having 7331 jets, and giving 
a light equal to that of 8100 candles, for about five hours daily ; 
and that, too, at a time, when a considerable portion of the gas 
is unavoidably wasted, by the daily opening of the main pipes, 
