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Evening Post, Volume CXII, Issue 123, 20 November 1931, Page 9

A small irregular chunk of the darker stone used' in the base of the campanile, was lifted by Dr. Marshall from a bath of one-to-one sulphuric acid, where it has lain; with frequent boilings, for five months; a polished face was still polished; cutting tool marka were perfectly plain on another face, and tha angles of fracture were still sharp. The one-to-one acid.test is ah exceedingly severe one, the reporter was told, but there was no change in the stone,-except that the tint was changed somewhat. Stone.tested in acid and then exposed to atmospheric conditions showed no signs of deterioration. .■ :■■■•■ ' .'■• - '■■■•■; ■ ■■ ' ■ • ■

Referring to tho rough tests made at tho Town Hall, Dr. Marshall said that they could not be regarded as tests at all. The lighter tinted stone which had discoloured was so close to tho ground as to collect dust and dirt, it was subjected to" the dripping from an old iron roof, and the vegetable growth which was complained of was a very common growth on Wellington buildings, and in that immediate locality was found on the Melbourne basalt of the foundation work of the Town Hall, upon the concrete of the hall, and on Port Chalmers breccia of a nearby building. ' No matter what stono might be used, concluded Dr. Marshall, discolouration from city dirt and soot was inevitable as time went on. He referred to the very marked discolouring of the State Pire Building as an outstanding example, and said that the markings were just soot and grime, with no reference of vegetable growth, and could be removed with water and a scrubbing b:ush. Tho sharp demarcation between clean stone and discoloured stone was brought about at the line whore tho beating of the weather commenced; thus below a'projection stretched a patch of discolouration where the stone was protected from tho beat of the

weather,