1907.] on Conservation of Historic Buildings and Frescoes. 599 



October 1, 1905 — the sulphuric acid from this source has trebled in 

 amount, the average during the twelve months preceding the 

 relaxation having been 11 J grains per 100 cubic feet, but in the 

 subsequent twelve months 33 grains.* And during the present year 

 so far there have been 43 grains in the same volume of gas.f If 

 sulphuric acid from coal-gas (like that from paraffin oil) contribute 

 in a comparatively small degree to the pollution of the general atmo- 

 sphere of London, vet it exerts a definitely injurious action when 

 produced in close proximity to an easily affected surface, such as 

 that of a fresco, within a building. Xo wonder that the delicate 

 film of calcium carbonate, the distinctive binding material in a 

 fresco, soon perishes under the onset of oil of vitriol. And here 

 let me anticipate, what I might have relegated to a later part of my 

 discourse, namely, a few words concerning the best-known frescoes 

 in the Palace of Westminster. I do this because the question of 

 sulphur in gas happens to have been brought into close connection 

 with these paintings in consequence of a Parliamentary paper pub- 

 hshed last year (Cd. 3085). For it has been urged, by one who 

 writes in the interest of the gas companies, that " the hydrochloric 

 and nitric acid vapours resulting from the electric arc-lamps in 

 nightly use in London are even more pernicious than the burning 

 of gas as at present manufactured." But it must be remembered 

 that analyses of London air find London rain prove that the pro- 

 portion of these acids present is quite insignificant compared with 

 that of sulphuric acid. The same writer states that five frescoes in the 

 King's Robing Room in Westminster Palace have required nothing 

 more than the removal of dirt. This remark is made in order to 

 discount a statement of mine in the Parliamentary Paper just named. 

 This statement runs thus : " The increased and increasing consump- 

 tion of coal in London, and the greater Ucence allowed to the gas 

 companies in the matter of freeing their gas from sulphur compounds, 

 must result in a serious augmentation of sulphuric acid in the air of 

 the Metropolis." But very much more than the removal of dirt was 

 needed. The frescoes are no longer frescoes. While retaining the 

 aspect of frescoes, they have been transformed gradually into paintings 

 which have had their original binding material replaced mainly by 

 ceresin and paraffin wax, unalterable compounds competent to 

 resist even sulphuric acid. But not only has the painted surface 

 required fresh protection, but the ground itself has had to be 

 strengthened by similar treatment, the plaster having been in many 

 places " sulphated " and thus rendered rotten. So the writer in the 

 Gas World of August 25, 1906, has not, as he says, hunted out " this 



* I have to thank Dr. F. Clowes, Chief Chemist and Superintending Gas- 

 Examiner to the London County Council, for his kindness in supplying me 

 with the official figures. 



t The corrosion of copper-boilers heated by gas is now so much more rapid 

 that their lives are shortened in the ratio 7 to 2. 



