ON THE RESISTANCE OF ROAD VEHICLES TO TRACTION. 377 



cooling purposes, and Signor Canovetti has shown evidence that a pei*- 

 forated surface will offer less resistance to the air than a plane one of 

 similar area. This is not of much advantage with an automobile as the 

 air, after having passed through the holes in the radiator, meets with 

 further obstacles in the mechanism inside the hood. 



With regard to the working parts situated under the car, these should 

 be made by the aid of inclined planes to cut tlie air rather than oppose it. 



M. Lavergne commends the suggestion of M. Forestier that different- 

 shaped bodies should be mounted on an electric chassis, and the total 

 resistance of chassis and body accurately measured, so that a really prac- 

 tical model could be designed. 



Power required hj Automobiles. 



Under this heading M. Lavergne has shown the enormous reduction 

 of weight per horse-power that has taken place during the last eight 

 years. In 1895, Levassor made the run from Paris to Bordeaux in a 

 4 horse-power car weighing about 1 ton, or 1 horse-power per 550 lb. dead 

 weight. In 1896 this weight was reduced to 365 lb. per horse-power ; in 

 1900 it fell to 90 lb. per horse-power. In the recent Paris-Madrid race 

 M. Cxobron Brillie appeared with a 100 horse-power car, the weight of which 

 represented only 22 lb. per horse-power. This weight has been still 

 further reduced in the case of motor bicycles, reaching as low a figure as 

 17 '5 lb. per horse-power. 



But there is not a corresponding increase in speed. In 1901 

 M. Fournier made over 53 miles per hour with a 28 horse-power Mors ; 

 last year M. de Knyff only slightly exceeded 58^ miles per hour with a 

 70 horse-power motor ; that is, an additional 40 horse-power. 



To what must this relatively small increase of speed be attributed ? 

 Air resistance is responsible for some increase but certainly not all. 



An extremely powerful motor must be accompanied by a comparatively 

 heavy load, otherwise the wheels do not ' bite ' well and energy is wasted. 

 It is well known that the modern racing-car skims along the surface of 

 the course, without sufficiently close contact between the wheels and the 

 ground ; in any case driving wheels should be more heavily weighted and 

 springs made less elastic. To reduce the power lost in vibration, the 

 engine should be more perfectly balanced, and, if necessary, the fly-wheel 

 and motor itself made heavier. ' AVho shall say,' M. Lavergne concludes, 

 ' whether, instead of building very powerful yet extremely light motors — 

 the durability of which is questionable — it would not be better to rest 

 content with a vehicle of smaller power, and use it more effectively? ' 



IV. Negotiations with the War Office. 



At a Committee Meeting held at the Society of Arts on May 15, 

 1903, it was proposed that as the expenses of this research were extremely 

 heavy it would be advisable to approach the Mechanical Transport 

 Committee of the War Office, in order to see if they Avoukl conduct the 

 experiments with heavy traction, as they had at their command various 

 powerful motors and traction engines, together with the necessary variety 

 of wheels. The Transport Committee in return would have the use of 

 the British Association recording instruments for their own experiments. 



This British Association Committee would have access to the in- 

 formation obtained which was of a scientific character with a view to 



