Although the problem of the stability of a fuselage that is subjected totorsional force is important in connection with the case of light metalconstruction of an aeroplane in flight, the theoretical side of the problemdoes not seem to have received much attention. This is probably because ofthe difficulty of obtaining its mathematical solution even in the case wherethe fuselage is assumed to be a circular hollow cylinder.Thus, I studied the problem in assuming that the fuselage is a cylindricalshell for the first approximation. Southwell and Skan have dealt with thestability of a plane elastic strip due to edge shearing forces, but theirresult cannot be applied to the problem of the cylindrical shell unless itslength is very short. Schwerin seems to be the only one who has written onthe torsional stability of a cylindrical shell. Although his method ofconstructing the differential equations of the equilibrium of a cylindricalshell has been chiefly derived from Love's text book, and appears correct inthe main, yet owing to the certain apparent particularities on his part hissolutions of equations are open to grave doubts.

In considering the design of marine aircraft, viz., flying boats andseaplanes, an entirely separate and additional subject is brought in forinvestigation, and upon which there would appear to be much reserve as todefinite formulations and data, etc. This subject, which I prefer to entitle“Hydrodynamics,” can become, besides interesting and absorbing, certainlymost deep in its complexity, and it is realised only too well by thoseactually engaged in such investigations, the more that time passes andexperience is gained.