Dew: Does it Rise or Fall?

Abstract

I AM sorry that Dr. Cohen thinks I misstated his views: but after comparing his letter (NATURE, Sept. 28, p. 482) and my letter (NATURE, Oct. 12, p. 578) very carefully I cannot see his point. I only referred to Dr. Cohen twice in my letter: in the first case I wrote: “Dr. J. B. Cohen … says it does both”, while his actual words were: “I think it may be said to do both”; in the second case I wrote: “Both Sir Herbert Maxwell and Dr. Cohen speak of the water vapour first condensing in the air before appearing as dew”; Dr. Cohen actually wrote: “The cold air tends to cool the objects with which it is in contact and the water vapour present in the warmer air is thereby condensed. Mist over water and marshy ground is formed in this way and this dew may therefore be said to fall”. I wish to be helpful in this correspondence, and if Dr. Cohen will be good enough to say in what particular he cannot accept my explanation of dew formation, I will do my best to elucidate the point.