The title of my paper should really have been “ Stability in Ordinary Conditions of Wind near the Ground,” to indicate that the stability about which I want to talk here to-night is not the equilibrium of a machine in calm air, or in an unfluctuating breeze (if there is such a thing), but the ability which a machine must have to remain stable under ordinary conditions of wind most days in the year. Although my ideas on feathering fans are brought in as one way of meeting the conditions which have certainly up to the present not been provided against in any experiment, I by no means hold by them if any better way could be devised for this vital purpose. Now the ordinary conditions of a breeze near the ground have been ably described by Sir Hiram Maxim and Professor Langley.