This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1920 edition. Excerpt: ...the force required to move a certain load on poor asphalt, best macadam and best gravel to be 26, 38 and 51 pounds, respectively. In the thirteenth annual report of the Board of County Road Commissioners of Wayne County, Michigan, it is stated that at a test made at Cleveland, in Novem'ber of last year, it was shown that less than half the quantity of gasoline was required to propel a given vehicle with a given load over an even, hard, concrete surface than was required to move the same vehicle and load over the same distance on the best type of earth road. The size of the wheels of the vehicles varies the tractive force, some engineers claiming that it varies inversely as the diameter, and others inversely as the square root of the diameter. In a paper read before the Surveyor's Institute, London, it is stated: From experiments made with Eastren and AndersonIs horse-dynamometer at the Royal Agricultural Show in 1874, a slightly greater ratio than inversely as the diameter was given, and I am inclined to think that inversely as the diameteris the more correct view of the two." This property is given a value of 22. Nor SLIPPERY. As is the case with traction, nearly all observations made with regard to slipperiness are not of much value for the present roads, as the standard generally was the number of times a horse slipped or fell down. Practically no data on this point for auto trucks are available at the present time. The condition of the surface is to be considered. A little loam may not be harmful when dry, but a little moisture will bake it very slippery, while a heavy rain will wash it off entirely. It can be accepted that the smoother the surface the more slippery it will be. Apart from the danger of overturning by...