2093. Coloured glass, however, notwithstanding the ingenious hypothesis which has been broached respecting it, does not appear to have succeeded in practice, and, indeed, none of the new kinds of glass that have been used since the reduction of the duty appear to have answered the expectations formed of them. Indeed, as Dr. Lindley very justly observes, 'it is improbable, to say the least of it, that any artificial light should be as well suited to plants as that which has been provided for them by the great Author of the universe.' 'Plants in hothouses are, however, necessarily exposed to a light rendered in some degree artificial by the glass through which it passes; and therefore it is really a serious question, what kind of glass is best suited to the purpose.' Dr. Lindley adds, that his own opinion is 'in favour of the whitest, as being that in which the three primitive colours are most entirely blended.' And this opinion will probably, in the end, prove to be correct, as light passing through a perfectly colourless medium must be most like the pure light of the open air.