The first suggestion that bacteria might be agents in stone decay was probably that of Buchanan (1904) in a paper read before the Royal Philosophical Society of Glasgow in 1904. This paper contained evidence that bacteria, yeasts and moulds were associated with the decay of sandstones in the City of Glasgow, and included a brief sketch of the manner in which the autotrophic bacteria, sulphur bacteria, iron bacteria, and the nitrifying bacteria might play a part in sandstone decay. This paper was apparently unknown to later writers, Anderson (1910), Marsh (1923) and Fox and Harrison (1925), none of whom makes reference to it. In 1928 Buchanan published the results afresh with no important addition, but confirming his earlier work. Stutzer and Hartleb (1899) in an important paper, published five years before that of Buchanan, noted the solution of the lime of the cement on walls of reservoirs and dock sides. While the greater part of this solvent action was believed to be due to dissolved carbon dioxide in the water, part of it at least was attributed to the action of bacteria contained in a brown slime which covered the walls.