54 
of them are not perfectly dry, the presence of moisture 
naturally favouring the formation of sulphuric acid, and also 
absorbing it when formed and assisting its action. In such 
cases I have known a most rapid action upon wallpapers of 
certain kinds and on organic materials where in contact 
with metals, notably brass, both the metal and the organic 
fibre being rapidly corroded. 
Many of the objects in the upper portions of rooms to 
which I ha ve alluded are replaceable, at some little expense of 
course, such as the colouring of ceilings and wallpapers, and 
we may make up our minds to putting up with their deteriora- 
tion for the sake of the excellent light and convenience of 
gas-lighting ; but to expose such objects as valuable pictures 
and books to the extensive action of the products of com- 
bustion of coal gas as we at present consume, is most inju- 
dicious, and is, there can be little doubt, the cause of a great 
deal of irreparable injury in many cases. My own opinion 
is, that now that mineral and other oils for illuminating 
purposes are so cheap, and lamps for their consumption are 
so admirably constructed and elegant in design, there is not 
the slightest reason why valuable collections of pictures and 
books should be exposed to the sulphurous emanations of 
coal gas. 
Since writing the above I find by an abstract in the 
Journal of the Chemical Society (1880, vol. ii., p. 836) that 
a Mr. W. R. Nichols confirms the generally accepted view 
that the deterioration of library bindings is mainly due to 
the action of the sulphuric acid from coal gas, and he finds 
that morocco is not so much affected as russia leather and 
calf skin, and that ordinary sheep skin is attacked by this 
body. 
Addenda. — For methods of estimating the sulphuric acid formed 
during the combustion of coal gas, and proof that suphuric acid is formed, 
see Young and others. Analyst, Yol I., p. 143.; Yol. II., pp. 66, 67, 118, 
133, 135, 139 ; and Yol, III., p. 201. For the effect of gas on the books 
of the Libraries of the Athenseum, London, Eoyal College of Surgeons, 
Portico Library, Manchester, and Literary Society, Newcastle-on-Tyne, 
see Dr. Letheby’s earlier reports to the London Corporation. 
