2090. British sheet glass was one of the first kinds generally employed in hothouses after the reduction of the duties. This glass being cast in plates of any size or thickness required, appeared exactly suited to meet the wishes of cultivators who required large panes; and it seemed admirably suited for horticultural purposes, as this kind of glass was beautifully clear and quite free from any colour. It was soon found, however, that in hothouses where this glass had been employed, the more delicate kinds of plants were 'injured by a sort of scorching when under the influence of the sun's rays in particular aspects.' Various causes were assigned for this effect; and, among others, Mr. Hunt, Keeper of the Mining Records at the Museum of Economic Geology, who had tried a great many experiments on the effects produced by coloured transparent media on the growth of plants, suggested the employment of tinted glass. To try the efficacy of his suggestion, Mr. Hunt had a number of small panes of glass manufactured of different colours, and endeavoured, by various experiments, to ascertain the effects of the different colours on the growth of plants.