ON DRAUGHT. 433 



he Jescribes Juno's chariot. He there says, while Juno was putting the 

 golden bits to tiie horses, Hebe fastened on the wheels to tlie iron axles. 

 " These wheels had eight brazen spokes, and the felloes were of gold, 

 and the tires of brass." — "The seal was fastened with gold and silver 

 cords." 



Tins, of course, gives us Homer's ideas of perfection in a chariot. 



All the epithets which could convey ideas of swiftness, were applied 

 to these chariots and to the horses, but we have no positive information 

 as regards the real velocity with whicii they would travel : as roads 

 were scarce, and probably at best merely tracks, much could not be 

 expected from vehicles constructed under such circumstances; the wheels 

 were small, from twenty to thirty inches in diameter, and all tiie parts of 

 the chariots were excessively heavy, so as to resist the repeated siiocks to 

 which they were sui)ject. 



The chariots represented upon the Frieze of the Parthenon, before 

 alluded to, and which is probably upwards of 2200 years old, are very 

 light in their construction, and only want springs to be called gigs. 



The advancement of all the branches of the mechanical arts has 

 necessarily introduced many improvements in the details of the construction 

 of the wheel itself, as well as that of the axle and the rest of the carriage, 

 and l)y this means no doubt increased very greatly the use and advantage 

 of it; but it is a remarkable fact, that tiiese improvements have been con- 

 fined exclusively to the workmanship and mechanical detail, and that the 

 principle has remained exactly the same, and has not even received any 

 addition during this immense lapse ol" time. 



Upwards of 3000 years ago, the wheels appear to liave been independent 

 of each other, and running upon fixed axles; we can say no more of the 

 most improved wheel of the most finished carriage of the present day. 



We are far from intending to cast any slight upon modern invention, or 

 to compare the groaning axletrees and creaking wheels of the ancients with 

 the noiseless Collinge's axles of the nineteenth century; but truth compels 

 us to acknowledge that a period of thirty centuries, more than half the 

 lime which is supposed to have elapsed since the creation of the world, has 

 produced no radical change nor brought into action any new principle in 

 che use of the wheel as applied to carriages. 



The particular form and construction of the wheel, as well as of all the 

 other parts of the carriage, however, admit of great variety, and the 

 draught is materially affected by their variation. We shall, therefore, 

 after examining the action of wheels in general, describe the mode of 

 construction now adopted, and then endeavour to point out the advantages 

 and disadvantages of the various forms which have been given to the 

 different parts of it. 



First, let us examine the theory of it, and suppose it acting on a level 

 plane. 



The wheel being a circle, the centre will remain always at the same 

 height, and consequently will move parallel to the plane in a perfectly 

 *evel line: if any weight be attached to or suspended from its centre, this 

 will also move in a continued straight line without rising or falling, and 

 consequently when once put in movement, there is nothing to check its 

 progress (neglecting for the moment the slight resistance of the air), and it 

 will require no force to keep in motion so long as the wheels continue to turn. 



We have therefore in this case only to examine into the force necessary 

 to turn the wheels. The wheels, if left to themselves, would roll on with 

 perfect freedom, whatever might be their weight, or whatever weight might 

 Ije attached to them, provid d nothing in the mode of attaching that weight 



