So 8 Observations upon Wheel- Carriage Experiments. 



fellow form a bended lever." This does not appear to me to 

 be the case. A thud point of force I conceive to be essentially 

 necessary to form a wheel or any other body iiito a lever ; this is 

 sometimes accomplished by a man applying his force to lift the 

 back part of a vvlieel, while the horse is perhaps endeavouring 

 to draw the carriage out of a rut. It does appear to me, that 

 a wheel as in ordinary to a carriage, does not resemble a lever 

 of any class, for the reasons following. All forces acting upon 

 the axle, either l)y gravity of the carriage or by any variety of 

 propelling forces, are resolvable into one force acting upon a 

 point within the wheel. All forces acting against the circum- 

 ference by obstructions or unevenness of the surface, upon which 

 the wheel moves, are also resolvable into one force acting upon 

 one point. We have now two forces acting against each other 

 in an inflexible line. When these forces are in direct opposition 

 to each other, the wheel stands still ; when they become so in- 

 direct as to overcome the friction, the wheel moves forward or 

 backward according to the direction of the impelling force of the 

 axle. There are, therefore, in my humble opinion, but two 

 forces and two points of force, mathematically speaking, in the 

 operation, whether a wheel be formed of spokes or of a solid mass. 

 Wheels in other machinery are often unquestionably levers, as 

 axis in peritrochio, or where two points of force happen to be at 

 different distances from the common centre in the same wheel, or 

 in inflexibly attached wheels; or where awheel moveable upon its 

 centre be used to transfer a force from one point of its circum- 

 ference to another, it umjuestionaljly becomes a lever*. 



If tlie foregoing observations should in anv degree tend to in^ 

 duce a finther course of experiments upon this subject of the 

 highest national importance, 1 cannot help entertaining the 

 Avarmest expectation, that the Report of the Committee given 

 in the Minutes of the Dublin Society of the thirtieth of 

 March last, (in consequence of which the experiments were 

 instituted,) recommending that " the relative advantages of tiie 

 different carriages be accurately and uvecjuiiwcally ascertained," 

 may be more reasonably complied with, and that the scientific 

 knowledge of that valuable body may be suital)ly assisted bv the 

 experience of practical agriculturists, so as to insure the exhibi- 

 tion of satisfactory and decisive evidence of the valuable truthsi 



• It would perliaps l)e reusonalilc for any one interested in this question, 

 to obtain in writins^ tlie nature of the ;innlus:y, that m;iy, by any niathetna- 

 tician, be supposed to exist between tlie iever and the opeiation of a wheel 

 with respect to a carriage. When on paper, such analogy may fairly 

 be serutinized ; but, if given verbally, it may be plausibly deceptive, or 

 counter to the doctrine of the resolution of forces on the definition of the 

 lever. 



relating 



