182 Dr Fyfe on the Comparative Value of Oil and Coal Gas. 
the junctures of the pipes are tight, there ought to be no escape 
of gas ; but, allowing that there is, it is fortunate, as I have be- 
fore remarked, that it is possessed of odour, because it gives us 
warning of its escape. 
That oil-gas does not contain any sulphuretted hydrogen, 
is allowed by all ; but that it is from this to be preferred to coal- 
gas, must not be taken for granted ; for though the gas given 
off from coal is at first loaded with sulphureous vapour, it is 
possible to free it entirely of it. Mr Neilson, Glasgow, in his 
report to the Dundee Company, states, that the gas made in the 
gas-works there is free from sulphuretted hydrogen, and does 
not tinge either silver or gilding. I have found the coal-gas of 
Edinburgh to be also free from it, as it did not discolour, in the 
slightest degree, paper dipt in a solution of sugar of lead, which 
it ought to have done, had it contained the smallest portion of it. 
It has been stated, that coal-gas has an advantage over oil-gas 
when required for street-lamps, because, as burners with very 
small holes are used for the latter, the flame is apt to be extin- 
guished by wind ; but this objection no longer exists, the small 
burners being laid aside for others, with holes a little larger, 
though not quite so much so as those used for coal-gas. Allow- 
ing, however, that the properties of oil-gas are such as to make 
us give it a preference, let us now inquire if it can be afforded 
as economically as that from coal. From what is already before 
the public, and perhaps the fullest account is to be found in the 
Dundee Report, it is impossible to come to any conclusion with 
respect to the profit likely to be derived from oil-gas establish- 
ments, they are so much at variance ; but, luckily, there is no 
necessity for having recourse to these calculations. Indeed, in 
attempting to find whether oil-gas can compete with coal-gas, I 
would throw them entirely aside, for why should we trust to 
speculations, when we have facts deduced from experience, to 
lead us to the decision of the question ? — I mean the expence of 
manufacturing the gases. 
In endeavouring, then, to answer this question with re- 
spect to their comparative merits, there are two circumstan- 
ces which ought to guide us, the comparative illuminating power 
of the gases, and the expence of making them. I have al- 
ready stated, at full length, the various opinions with respect to 
