448 ON DRAUGHT. 



the more effect will it produce in diminishing' the draught : with a C spring* 

 a very contrary effect is produced. 



A carriage hung upon C springs may certainly be made the most com- 

 fortable to the rider, but all the ease that can be required, and much more 

 than is found in the generality of post-chaises, may be obtained by well- 

 constructed grasshopper springs, and with considerable advantage to the 

 horses. 



The practice of loading coaches as high as possible to make them run 

 light, as the coachmen have found by experience, is only a mode of assist- 

 ing the springs. The mass being placed at a greater height above the 

 wheels, acting at the extremity of a longer lever, is not so easily displaced 

 laterally by any motion of the wheels, which, therefore, may rise and fall on 

 either side as they run over the stones, without producing any sudden con- 

 cussions upon the load, which swings to and fro with long, easy move- 

 ments ; it is probable also, that the weight, being thus swung from side to 

 side, may, upon good roads, diminish the draught, as it is in fact generally 

 running upon two of the wheels ; while, in the other direction, it equally 

 admits of the front and hind wheels successively passing over any impedi- 

 ments ; and yet, by the manner in which it is fixed upon the springs, it 

 does not admit of any longitudinal elasticity. 



The fact of coaches thus loaded running light has been clearly proved 

 by the failure of what were called Safety Coaches, in which the only differ- 

 ence consisted in placing the load very low. These coaches, although 

 completely answering their purpose of safety, were discontinued solely, we 

 believe, from their being found destructive of the horses. 



Experiments, nevertheless, have been made to prove that this w^as only 

 an idle prejudice of coachmen ; but universally received opinions, even if 

 leading to erroneous conclusions, which is hardly possible, must always 

 have some good foundation ; and coachmen, although they may not have 

 been so much so at the time these experiments were published (in 1817), 

 are certainly now rather an intelligent class of men. We should, therefore, 

 prefer risking a theory, if a theory were necessary, in support of their pre- 

 judices rather than in opposition to them. The experiments alluded to 

 were not, in our opinion, made under the circumstances which occur in 

 practice. Small models (the wheels being seven inches in diameter) were 

 drawn along a table across which were placed small strips of wood to 

 represent the obstructions met with in a road ; but these strips of wood 

 came in contact with each pair of wheels at the same time, and never 

 caused any lateral motion. They produced, therefore, a totally different 

 effect from that which takes place in a road, where the action rarely affects 

 more than one wheel at a time, or if two, they are almost invariably those 

 two on the same side of the carriage ; consequently, in the model, the 

 wheels in passing over an obstruction, threw the whole weight backwards 

 in a direction exactly opposite to the movement required ; while in practice, 

 the carriage is generally thrown sideways, which does not affect its forward 

 motion. 



The conclusions drawn from these experiments are, therefore, as might 

 be expected, at variance with practical results, and directly contrary to the 

 opinions of those whose daily experience ought to enable them to judge 

 correctly. 



The effects, also, of velocity and momentum must be difficult to imitate 

 in models. 



The advantage of placing the load high will not, however, equally apply 

 at low velocities, still less when springs are not used : it may frequently, 

 indeed, in the latter case, produce quite a contrary effect. 



