The aerodynamic resistance of wires. The apparatus used in these experiments was described by the author in his f Report to the Laboratory Committee of the Aeronautical Society of Great Britain. When the experiments herein described were started in 1910 no information on the resistance of wires and ropes was available, but the following papers have since been published :— “ The Resistance of Wires and Ropes in a Current of Air,” by B. Melville Jones, B.A. ; “ Comparison of the Resistances of Stationary and Vibrating Wires,” by T. E. Stanton, D.Sc, M.I.C.E. (Report of the Advisory Committee for Aeronautics, 1910-11) ; and “ The Tests of Smooth Wires and Wire-ropes made at the Gottingen “ Modellversuchsanstalt “ (Ztsch. fur Flugtechnik und Motorluftschiffahrt, Oct. 29th, 1910). Owing to the absence of funds the experiments of the resistance of wires have not been carried to a conclusion. The following data and conclusions are derived from a series of preliminary or trial experiments. They are published herewith for the guidance of future experimenters.

The shielding effects of struts and bars. In the previous communications, I., II., and III., the aerodynamic resistance of single bars, struts, and wires was investigated. The object of the investigation herein described was to determine the shielding effect of one bar mounted in the direct path of another bar of identical length, shape, and size.

Method of mounting the specimens. The upper bar was suspended from the fork of the balance at two points 6 inches apart in the manner described in communication II., and the identical lower bar was pivoted to the upper bar by two parallel wires 6 inches apart. Means were provided to allow the lower bar to be gradually lowered away from the upper bar. The axis of the bars were kept parallel and the ends of the two bars were kept exactly beneath one another throughout the experiments. All the bars were 24 inches long and $ inch thick.

The following tables are compiled from tests carried out at East London College on various materials of aeroplane construction, kindly supplied by Messrs. W. N. Brunton and Son, T. W. K. Clarke and Co., F. Handley Page, and H. EoUet and Co. Figure 1 shows the method of fixing the steel tapes during test. Table I. gives the results of these tests.

If one reflects on the great army of scientific men who are at present studying the subject of the motion of planes, at an angle, in fluids, it is very remarkable that the work of Avanzini on this subject should have escaped notice. All that appears to be known about this diligent experimentalist is in reference to what is known as “ Avanzini's law,” in relation to the position of the centre of pressure on a moving plate. This law is quoted by Professor Bryan and M. Alexandre See (to quote two only of the most eminent writers on the subject), but they omit to say from whence they get the formula. M. Alexandre See, in a private letter, has kindly informed me that “ je crois qu'on a appele ‘ Loid ‘ Avanzini ‘ une loi qu'il n'a jamais formulee lui mime., mais qu'il a etudiee.” Whatever Avanzini may have said on the subject is probably to be found in the Memorie della Academia di Padova, but the volume containing his memoir does not appear to be in England; in any case 1 have not been able to find it.