360 



SCIENCE 



[N. S. Vol. L. No. 1294 



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 require- 

 ments as regards supply. The total horse- 

 power produced in the last twelve montlis 

 of the war approximated to eight millions 

 of brake horse-power, a figure quite com- 

 parable 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 flight, how- 

 ever, I feel that it may be opportune to 

 make the following observations on the 

 comparative utility of aeroplanes and air- 

 ships for commercial purposes. In the 

 case of the aeroplane, the weight per horse- 

 power increases mth the size, other things 

 being equal. This increase, however, is 

 met to some extent iby a multiplicity of 

 engines, though in the fuselage the in- 

 crease 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 pro- 

 portion to the dimensions, other things, 

 including 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 ; and one of 1,500 feet in length and 

 8X60 = 480 tons displacement would re- 

 quire only 2^ 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 Northeast Coast Institution of Engi- 

 neers and Shipbuilders, July, 1919. 



"With the same proportion of weight of 

 hull to displacement, the larger airship 

 would stand double the wind-pressure, and 

 would weather storms of greater violence 

 and hailstones of greater size. It would 

 be more durable, the proportional upkeep 

 would be less, and the proportional loss of 

 gas considerably less. In other words, it 

 would lose a less proportion of its buoy- 

 ancy per day. It is a development in 

 which success depends upon the project 

 being well thought out and the job being 

 thoroughly well done. The equipment of 

 the airsheds with numerous electric haul- 

 age winches, and all other appliances to 

 make egress and ingress to the sheds safe 

 from danger and accident, must be ample 

 and efScient. 



The airship appears to have a great 

 future for special commerce where time is 

 a dominant factor and the demand is 

 sufficient to justify a large airship. It 

 has also a great field in the opening up of 

 new countries where other means of com- 

 munication are difficult. The only limita- 

 tion to size will be the cost of the airship 

 and its sheds, just as in steam vessels it 

 is the cost of the vessels and the cost of 

 deepening the harbors tliat limit the size 

 of Atlantic liners. 



Such developments generally take place 

 slowly, otherwise failures occur — as in the 

 case of the Great Eastern — and it may be 

 many years before the airsliip is increased 

 from the present maximum of 750 feet to 

 1,500 feet with success, but it will as- 

 suredly come. If, however, the develop- 

 ment is subsidized or assisted by the gov- 

 ernment, incidental failures may be faced 

 with equanimity and very rapid develop- 

 ment accomplished.^ In peace-time the 

 seaplane, aeroplane and airsliip will most 

 certainly have their uses. But, except for 

 special services of high utility, it is ques- 



3 The literature on this subject includes an article 

 which appeared in Engineering on January 3, 1919. 



