president's address. 15 



insulated cable laid on the bottom of the sea, earthed at the further 

 end, and through which an alternating current is passed. By means 

 of delicate devices installed on a ship, she is able to follow the cable 

 at any speed with as much precision as a railless electric 'bus can 

 follow its trolley wire. Cables up to 50 miles long have been used, 

 and this device promises to be invaluable to ships navigating narrow 

 and tortuous channels and entering or leaving harbours in a fog. 



Aircraft. — It may be justly said that the development in air- 

 craft design and manufacture is one of the astonishing engineering 

 feats of the war. In August 1914 the British Air Services possessed 

 a total of 272 machines, whereas in October 1918, just prior to the 

 Armistice, the Eoyal Air Force possessed over 22,000 effective machines. 

 During the first twelve months of the war the average monthly delivery 

 of aeroplanes to our Flying Service was fifty, while during the last 

 twelve months of the war the average deliveries were 2,700 per month. 

 So far as aero-engines are concerned, our position in 1914 was by no 

 means satisfactory. We depended for a large proportion of our supplies 

 on other countries. In the Aerial Derby of 1913, of the eleven machines 

 that started, not one had a British engine. By the end of the war, 

 however, British aero-engines had gained the foremost place in design 

 and manufacture, and were well up to requirements as regards supply. 

 The total horse-power produced in the last twelve months of the war 

 approximated to eight millions of brake horse-power, a figm-e quite 

 comparable with the total horse-power of the marine engine output of 

 the country. - 



Much might be written on the progress in aircraft, but the subject 

 will be treated at length in the sectional papers. In view of the recent 

 trans-Atlantic flights, however, I feel that it may be opportune to make 

 the following observations on the comparative utility of aeroplanes and 

 airships for commercial purposes. In the case of the aeroplane, the 

 weight per horse-power increases with the size, other things being equal. 

 This increase, however, is met to some extent by a multiplicity of 

 engines, though in the fusilage the increase remains. 



On the other hand, with the airship the advantage increases with 

 the size, as in all ships. The tractive effort per ton of displacement 

 diminishes in inverse proportion to the dimensions, other things, includ- 

 ing the speed, being the same. Thus, an airship of 750 feet length 

 and 60 tons displacement may require a tractive force of 5 per cent., 

 or 3 tons, at 60 miles per hour; while one of 1,500 feet in length and 

 8x60=480 tons displacement vsould only require 2i per cent, x 480 = 12 

 tons at the same speed, and would carry fuel for double the distance. 



^ See Lord Weir'.s Paper read at the Victory Meeting of the North-East 

 Coast Institution of Engineers and Shipbuilders, July 1919. 



