1815.) Experiments on the Draught of Carriages, 107 
an advantage over that without springs of one-fourth of the weight 
that was laid upon it. 
mt Experiment II. 
Two post-chaises, weighing each 12 cwt. 7 lb. one of them 
painted black, the other white, were next compared ; the perch of 
the black one was moveable, so that it could be lengthened or 
shortened at pleasure. 
When their perches were of equal length, viz. of seven feet six 
inches, the carriages were compared previous to these experiments, 
and their draft was equalized by an addition of weight to that which 
‘ran the lightest. 
The perch of the black carriage was now lengthened to ten feet 
three inches. The carriages were each of them loaded with 2 ewt. 
They now nearly kept pace with each other, the one with the 
long perch appearing to have rather the advantage. 
Experiment III. 
The load, which in the former experiments was placed in the 
bottom of the white carriage, was now placed in an imperial on the 
top. The removal of the weight four feet higher from the ground 
did not promote the progress of the carriage, which did not yet 
keep pace with the black carriage. : 
Experiment IV. 
Two similar Scotch drays, one of them painted biuve, and the 
other red, were now compared. They had been brought to an 
equal weight; and the blue carriage was supported upon wooden 
rings, consisting of two pieces of elastic timber, connected with 
the bottom of the dray by iron shackles ; each dray was loaded with 
6 cwt. 
The (blue) dray upon springs had now a weight of 12 ewt. placed 
upon it. With this additional weight, however, it got before the 
(red) dray which had no springs. 
From this experiment, the application of wooden springs to carts 
upon pavements, or upon ordinary roads, appears to have an ad- 
vantage in the proportion of 71. to 6. It must be observed, that a: 
perfect coincidence of draft could not be obtained; because the 
carriages to be compared rolled upon different tracts of the pave- 
ment, so that the smallest inequality of the roads must have made’ 
some difference in the relative progress of the carriages; but to 
make as fair a comparison as possible between their drafts respect- 
ively, that carriage which was placed on the northern track, as the 
carriages went from east to west, was in its return placed on the 
southern track. 
Some small variation of the draft might be occasioned bythe 
elasticity of the long perch, and some by the vibratory motion of 
the fore carriage, which was drawn by a single rope. But to those 
fonversant with the subject, these slight variations were but of little 
moment, 
