1815.] Tlumination by Coal Gas. 7 
The heating of the gas furnace, the charging of the retorts with 
coal, the closing them up air-tight, and keeping them red-hot, are 
the only operations required in this art ; and these demand no more 
skill than a few practical lessons can teach to the meanest capacity. , 
The diversified experiments which have been made by different 
individuals unconnected with each other have now sufficiently esta- 
blished the perfect safety of the new lights, and numerous manu- 
factories might be named in which the gas lights have been in usé 
for upwards of seven years, where nothing like an accident has 
occurred, though the apparattis in all of them is entrusted to the 
most ignorant man. 
That coal gas, when mixed with a certain portion of common 
air in close vessels, may be inflamed by the contact of a lighted 
body, is sufficiently known. But the means of preventing such an 
occurrence in the common application of this species of light are so 
simple, easy, and effectual, that it would be ridiculous to dread 
dangers where there is nothing to be apprehended. | 
In speaking thus of the safety of this new art of illumination, it 
would nevertheless be easy to name instances where explosions have 
been occasioned, but solely through egregious mistakes having been 
committed in the erection of the gas light machinery, were this @ 
subject on which I meant to speak ; but as I do not, I shall merely 
mention, on the present occasion, that an explosion very lately took 
any in a manufactory lighted with coal gas, in consequence of a 
arge quantity of gas escaping (from the gazometer being over- 
eharged with gas) into the gazometer house, where it mingled with 
common air, and was set on fire by the approach of a lighted 
candle. That such an accident could happen, is an evident proof 
that the apparatus for preparing the gas was a bad one, because 
such an accident might have been prevented effectually by adapting 
a waste pipe to the gazometer, as well as to the gazometer house. 
By this means, if more gas had been prepared hy a careless operator 
than the gazometer could contain, the superfluous quantity could 
hever have accumulated, but must have been transported out of the 
building into the open air, in as effectual a manner as the waste- 
pipe of a water cistern conveys away the superfluous quantity of 
water when the cistern is full. 
In answer to the second question made by your Correspondent, 
namely, what sort of coal is to be prepared for producing the gas, 
it remains to be observed, that Cannel coal produces thé very best 
fas or at least the gas which it affords requires the least trouble of 
eing purified and rendered fit for illumination ; though Newcastle 
coal is employed for illumination in this metropolis.* But the 
* The public buildings already illuminated in this town with coal gas are the 
following: the church of St. John the Evangelist, the avenues to the House of 
rds and House of Commons, Wesminster Hall, the Admiralty, the house and 
offices of the Speaker of the House of Commons, the Mansion House, the whele 
jiberty of Norton Falgate, &c.; and the total length of pipe laid down as mains 
j0 the streets of London amounts already to 15 miles, ‘ 
Vor, VI, N° I. B 
