Ever and again in the history of aëronautical development during the last century there occurred a movement in favour of the hélicoptère or vertical screw machine, and now when flying machines have advanced to a practical stage the question again appears. Many will have doubtless followed with interest the series of letters which has been appearing in “Engineering” since early in the year, in the course of which several engineers of repute have advocated the hélicoptère in no uncertain manner.