A very large amount of valuable work has been done in measuring the forces on models of aeroplane surfaces placed in a wind channel, and the results obtained are of the greatest value to the designer. Doubt has however been thrown on the applicability of the results obtained to calculations referring to the full–size aeroplane in flight, and it is of great importance to obtain definite information regarding the corrections, if any, which should be applied to the wind channel results. The experiments described below were made with the object of comparing the pressure-distribution on an aeroplane wing in flight with the distribution measured on a model of the same wing in a wind channel. The measurements were carried out on an aeroplane constructed by the writer, which for the purpose: of the experiments was flown over the sands at Llanddona, on the east coast of Anglesey. The beach at this place is an ideal one for experiments of this nature, there being a stretch of hard level sand obtainable fully three miles long and over a mile broad.

I t is perhaps unfortunate, from the point of view of aviators, that the extinct flying reptiles known as “pterodactyls” or “pterosauria” no longer exist. There can be no doubt, that in the case of the more highly evolved members of the group the organisation was more specialised for flight than that of any other animal of which we have knowledge. Other flying animals can walk, run, or swim, besides fly. But in the case of the higher pterodactyls their structure is such that it is difficult to understand how they can have had any other means of progression than flying. With a body little larger than that of a cat they had a span of wing asserted in some cases to have reached 21 feet or more.

In view of the very interesting information about pterodactyls contained in the foregoing paper by Dr. Hankin and Mr. Watson it will be worth while to endeavour to reconstruct the animal and to ascertain as far as possible the effect of the various adjustments upon the shape of the membrane which forms the wing.

This can best be accomplished by a study of the drawings accompanying this paper.

In the first place, it is important to remember that the wing membrane (plainly visible in some of the smaller fossils) doubtless resembled that of a bat in being extremely extensible and elastic. Possibly it had muscles attached to it which could tighten it in various directions and possibly increase and diminish camber. Air pressure upon this membrane would be certain to make the back margin of the wing a curved line with the convexity upward and the front margin of the wing (formed chiefly by the supporting bones) would have to follow this curved line more or less closely, otherwise the angle of incidence would vary excessively in different parts of the wing.

A short summary of our knowledge of this subject may be of interest to readers of the Aeronautical Journal.

Dust devils, that is to say, columns of dust in rapid rotation, are occasionally seen in Agra. They only occur in hot, dry weather. Those of the largest size, having a diameter of two or three metres and a height of several hundred metres, only occur when the air is nearly calm. They travel to leeward at a speed of about four to six miles per hour. The dust, having reached the upper end of the column, spreads out into a diffuse, irregular mass, which may persist for some time after the dust devil that produced it has vanished.

Fig. i is copied from a book treating of dust devils and dust storms observed at and near Lahore (India) by P. F. H. Baddeley.

He states that they are never shaped like an inverted funnel, as is the case with whirlwinds in America, as described by Redfield.