ON DRAUGHT. 563 



degree of perfection in those essentials for a good road hardness and smoothness 

 of surface for the wheels to roll upon. It requires, however, that the carriages 

 should be all nearly alike, as regards the width and form of the wheels ; and 

 experience has proved that such a road is not generally worth constructing, 

 unless the traffic is sufficient to allow of carriages being built expressly for that 

 or similar roads. This being the case, the form and dimensions of the rails, 

 and the general construction of the carriages, are uncontrolled by any other 

 consideration than that of diminishing draught. 



A considerable improvement upon this point may, therefore, be expected in 

 the railway over the common road. A railway, as now constructed, consists 

 simply of two parallel bars of iron, having a flat upper surface of about two 

 and a half inches wide. With the exception of this surface, the forms adopted 

 for the bars are various, depending principally on the mode selected for sup- 

 porting them, some resting on and secured to blocks of stone, placed at intervals of 

 about three feet others secured in like manner to " sleepers," or beams of wood 

 which are placed transversely, resting on the ground ; while according to a third 

 system the bars are secured along their whole length to longitudinal timbers. 

 The wheels at the present time, generally made of wrought iron, and from 3 to 

 4 feet in diameter, are made" slightly conical with a flange about one inch deep on 

 the inner side. This slight flange, and the cone of the wheel which is also very 

 slight, are found sufficient to keep the wheels from running off the rails, even at 

 the highest velocities. This brief description is sufficient to give a general idea 

 of the construction of railways, which is all that is necessary for our present 

 purpose. It will be easily conceived that hard, cast-iron wheels, running upon 

 smooth edges of iron hi this manner, can meet with but little resistance except 

 that arising from friction at the axle. Accordingly we find, upon a well-con- 

 structed railway in good order, that the resistance at moderate velocities does 

 not exceed, in any sensible degree, that which must arise from this cause. It 

 has been found that a force of traction of lib. will put in motion a weight of 

 200, 300, and even, hi some cases, 350lbs. : so that a horse, exerting an effort of only 

 125lbs., would drag on a level 12 or 14 tons. This is ten or twelve times the 

 average effect of his work upon a good common road, and, as it arises entirely 

 from the hardness and smoothness of the surface, we cannot conclude our 

 observations by a more striking and unanswerable argument than this, in proof 

 of the immense advantages and saving of expense which would result from 

 greater attention to the state of the roads. 



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