Dummies are particularly suitable for use in camouflaging operational aerodromes; they not only serve to mask the aircraft and equipment stationed thereon, but also make it possible to give the flying field the aspect of being unusable for flying purposes.

In recent wartime practice, dummies have been extensively used for aerodrome camouflage, and have proved particularly effective, since an enemy flying over the area in which an operational aerodrome is situated, will usually omit to take notice of dummies imitating local features of the landscape, and concealing the purpose for which the terrain is actually being used.

The following paper forms a continuation of a recent work by Prandtl (I) “On the Calculation of Boundary Layers.” It deals with the problem of developing in detail the method, proposed in that paper, for continuing a given velocity profile in a laminar boundary layer when the pressure distribution is given; the method is tried out in practice by numerical evaluation of an example.

It is shown that the calculation of the critical loads of a plane framework is superfluous if the bending moments in the bars due to external moments and to lateral loads are determined by the Hardy Cross moment distribution method as extended by James. Convergence of this method is a proof of the stability of the framework. In Section 1 methods of determining stresses and critical loads in frameworks are discussed. Section 2 deals with the distortion patterns of beam columns on several supports below and above the critical loads. In Section 3 the method of proof of the convergence is outlined, and regular and particular cases are discussed with the aid of numerical examples. The final proof is given in Section 4.

The Theorem of Three Moments in a simple form, referring to bending moments at any three consecutive supports A, B, C, of a continuous beam uniform in each bay, AB = a, BG = c, takes the form

w and being constant load intensities over AB and CB respectively.

On p. 159, Vol. 42 (1938), of this journal, Capt. J. Morris discussed a modification in this case (and in the more general case when the beam is in thrust) when the load intensity varies according to a parabolic law.