stated. I became therefore a student of theory and literature for a time, I hit upon the string of considerations that led me to what is called Ponderevo's Principle and my F.R.S., and I worked this out in three long papers. Meanwhile I made a lot of turntable and glider models and started in upon an idea of combining gas-bags and gliders. Balloon work was new to me. I had made one or two ascents in the balloons of the Aero Club before I started my gasometer and the balloon shed and gave Cothope a couple of months with Sir Peter Rumchase. My uncle found part of the money for these developments; he was growing interested and competitive in this business because of Lord Boom's prize and the amount of réclame involved, and it was at his request that I named my first navigable balloon Lord Roberts Alpha.
Lord Roberts α very nearly terminated all my investigations. My idea both in this and its more successful and famous younger brother Lord Roberts β was to utilize the idea of a contractile balloon with a rigid flat base, a balloon shaped rather like an inverted boat that should almost support the apparatus but not quite. The gas-bag was of the chambered sort used for these long forms, and not with an internal balloonette. The trouble was to make the thing contractile. This I sought to do by fixing a long fine-meshed silk net over it that was fastened to be rolled up on two longitudinal rods. Practically I contracted my sausage gas-bag by netting it down. The ends were too complex for me to describe here, but I thought them out elaborately and they were very carefully planned. Lord Roberts α was furnished with a single big screw forward and there was a rudder aft. The engine was the first one to be, so to speak, right in the
