The effect of dew in protecting vegetation every clear still night of summer was long ago pointed out by Dr Wells; the correctness and acuteness of whose views on this subject have been generally recognised. The hypothesis recently put forth by Dr Tyndall, that absorption of radiant heat by aqueous vapour in the atmosphere is an effective defence against destructive degrees of cold, and the ready acceptance yielded to it by some of our highest authorities in the popular promulgation of the truths of science, seem to render it necessary to recall attention to Dr Wells' admirable work.