oh Experiments upon Wheel-carriages* 93 



the rope which goes round it, the whole machine was so raised 

 as to place the wheel in a vertical situation, and one hundred 

 weight heing suspended at each end of a rope that went round 

 this pulley, their equipoise was overcome by placing half a pound 

 on either one side or the other. 



To compare the draft of two carriages by means of this wheel, 

 one end of a rope passing round it must be fastened to one car- 

 riage, and the other end to another ; if, then, the peirameter be 

 drawn forward, the carriage which moves the easicbt will get ' 

 before the other, and by adding weights to that which gets fore- 

 most, until both proceed together, the weight thus added be- 

 comes a measure of the advantage in the construction of one of 

 these carriages over the other, or of the roads upon which they 

 move. It must be observed, that the draft of carriages thus 

 compared, is not to be determined by one of them preceding the 

 other, but by the u'eight luh'ich produces an equaiily of draft. 



Two parallel roads, or trackways of deal plank, were laid so 

 as to be level in every direction ; all the carriages used in these 

 experiments were guided upon the roads by a guide-rail placed 

 between the planks. The pole of each carriage was provided 

 with brass rollers, which ran on each side of the guide-rail to 

 prevent the friction, and uncertainty of fiaunches, and guide the 

 carriage when drawn forward.* 



To overcome the vh ineriice of the carriages before they were 

 brought into competition, a detent was applied to the peirame- 

 ter, so as to prevent it from revolving till the carriages had ad- 

 Tanced some yards. Pieces of wood, five-eighths of an inch in 

 height, were nailed upon each of these trackways, to represent 

 the mean inequalities of a road, which had been ascertained by 

 Mr. Edgeworth, by a contrivance of his invention, to be equal 

 to that height. 



Comparison of Axlclrces by means of Ike Peirameter. 



A carriage with a straight axletree, greased with anti-attrition 

 compo'^ition, was compared with a carriage having Coilinge's 

 patent axletree, eacii weighing 3 cwt. S qrs. 7 lbs. 



crct. (jrg. 



The straight axletree was loaded with . . .3:0 

 Coilinge's with . , . . . . . . 0:2 



When drawn forward on the smooth j)lank road, by the peira- 



iTietcr, they kept together. 



Comparison of Axle trees ly means of a fixed Vullcy. 



A carriage of cc(ual weight, mounted on wheels, of Messrs. 

 Bonnie, wa-j compared with the two former ; each was loaded 

 with ti cwt. 



On 



