Olservntions vpon Wheel-Carriage Experiments. 257 



yard, and ten from tlie south side, the cart to the southward was 

 'verv much lower than the other, a fact that is particularly well 

 wonh attention. They should therefore have been pennUted 

 to return upon their 'respective tracks, as this would have 

 shown the disparity in point of surface; or had they been brought 

 back to the east side and again started, having changed places, 

 the difference with respect to road would likewise have been as- 

 certained. The carts, with the view of counteracting the effect 

 of any disparity of road, were erroneously made to change places 

 at the west end of the track ; but this was as deceptive as be- 

 fore, because the cart upon the south side, that had the advan- 

 tao-e of fall of ground in its first progress, was again given the 

 ad^'antage by being placed to go back upon the north «'de hori- 

 zontally-, while the other, now put to the south side, was obliged 

 to CO back, ascending the rising ground. . ., . . . . 



These circumstances with their various dissimilarities, and the 

 unsuitabilitv of an exi)eriinent, where the weight of the loading 

 was inferior to the weight of the cart, and that a heavy cart sup- 

 ported upon light springs unfit for a weighty load, render it im- 

 possible in mv huml)le opinion, to collect any accurate or useful 

 information from this experiment. Carts of the weight and 

 strength, in this case used, commonly draw a ton or thirty hun- 

 dred woi^ht. . , 



I hope I may not be thought presumptuous, when I say that 

 the construction of wheel carriages, particularly with regard to 

 the difference of the effect of weight of body and weight of 

 wheels, questions distinct that have hitherto been confounded, 

 and the application of the force of horses to carriages, are all 

 of them subiects more unconnected than is commonly supposea, 

 and very much in their infancy with respect to public knowledge 

 Many practical errors have of late years been discovered, and 

 mucli useful instruction is no doul)t yet to be receive, . 



I cannot lieh) believing, although with very muc.i dcierence to 

 the hi-h authorities upon this subject, that there is an error in 

 considering wheels in their ordinary application to carnages as 

 levers Mr. Edgeworth, in his work upon Roads and Wheel 

 Carriages, page 75, considers them as such. He mentions two 

 questions having taken up much time of a committee of the 

 House of Commons of England, that sat lor ten years upon the 

 subjects of roads and wheel-carriages. The one was Do the 

 spokea of a wheel on a level road act as levers ? ^he other 

 « What has l>eeii the cause, and what is the use of dishing 

 wheels '" To this latter ciuestion every one can give the answer. 

 I cannot, however, with respect to the former question, agree 

 with Mr. Edgeworth when he says, "Whoever looks at a wheel 

 coing over an obstacle, must see that the spoke and part ot the 

 Vol.46.No.2iO. OcM815. R f^"«^v 



