IS 15.] Draught of Carriages. 1 71 



waggoner or coachman by experiments on the modeh of coaches or 

 waggons. It has been hitherto, therefore, a desideratum in 

 mechanics to discover means of ascertaining precisely the power 

 exerted by animals in drawing instruments of agriculture, as well as 

 what is requisite to draw wheel carriages. 



A machine for this purpose was presented to the Society for the 

 Encouragement of Arts and Manufactures in 1771' It consisted of 

 levers acting upon a spiral spring, in such a manner as to move an 

 index that went through a considerable space. But as the power of 

 the horse, and tlie resistance of the machine, varies continually ; 

 and as this machine showed only the greatest exertion of the power, 

 without giving the sum of all its efforts, it was not satisfactory. It 

 is possible to construct a machine upon this principle that will give 

 the amount of the time and force employed in trials of this sort j 

 but more simple and satisfactory means have been discovered. 



In page 50 of the first Report for May, 1S08, of the Committee 

 of the Highways, I have spoken of a perfect method of ascertaining 

 the comparative force necessary to draw any two carriages. It 

 appears to me to be my duty * to describe this contrivance in the 

 present paper. 



To elucidate the principle of this apparatus, two post-chaises 

 were selected, the weights of which were nearly tiie same, their 

 wheels were nearly of the same size, and they were alike in their 

 general construction. To determine which of these could be drawn 

 over the same obstacles with the greatest ease, one end of a rope 6"0 

 yards long was fastened to the splinter-bar of one of tlie chaises, and 

 the other end of it was fastened to the splinter-bar of the other car- 

 riage. This rope had been previously made to pass round a light 

 pulley six feet six inches diameter, which was placed horizontally, 

 by means of a proper frame, on a two-wheeled carriage. 



This pulley was sufiicicntly large to permit the carriages which 

 were to be compared to run in a parallel direction at a sufBcient 

 distance from each other. 



The foremost carriage was drawn forward by horses, and the two 

 chaises were obliged to follow it. As the chaises were nearly of the 

 same weight, they kept for some time together ; but when cither of 

 them was retarded, it fell behind the other. An inconsiderable 

 ditll'rence in the goodness of the parts of the road on which either 

 L-arriage ran bc'Came sensible by ilic retardation of thut cairiage 

 which ran upon the worst road. 



If the machine carrying the pulley be drawn forward, the two 

 other carriages must follow it ; and if they are of equal weight, and 

 equally well constructed, they must move on together, as they are 

 drawn by the carriage with tlie pulley, provided the part of the 

 road on which each of ihrm moves be equally smooth and good ; 

 but if cither of the carriages that arc to be compared is inferior in 



• Ttiis r««ay was composed ae the diiirc of llic Chairman of the Committcp of » 

 Ibc House of C'JiniiHins. 



