ON DRAUGHT. 573 



pected in the railway over the common road. A railway, as now con- 

 structed, 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 prmcipally 

 on the mode selected for supporting them, some resting on and secured to 

 blocks of stone, placed at intervals of about thi^ee feet— others secured m 

 like manner to ' sleepers,' or beams of wood which are placed transversely, 

 restino- 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 m 

 diameter, are made shghtly conical with a flange about one inch deep on 

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

 very shght, are found suf&cient to keep the wheels from running oft the 

 rads, even at the highest velocities. This brief description is suflacient to 

 oive'a general idea of the construction of raHways, which is all that is 

 necessary for our present purpose. It mil be easily conceived that hard, 

 cast-ii'on wheels, running upon smooth edges of iron m this manner, can 

 meet with but httle resistance except that arising from friction at the axle. 



Accordingly we find, upon a well-constructed railway m gooa order, 

 that the reststance at moderate velocities does not exceed, in any sensible 

 deo-ree that which must arise from this cause. It has been found that a 

 for°ce of traction of 1 lb. will put in motion a weight of 200, 300 and even, 

 in some cases, 350 lbs. ; so that a horse, exerting an effort of only 125 ibs., 

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

 averao-e effect of his work upon a good common road, and, as it arises 

 entirely from the hardness and smoothness of the surface, we cannot con- 

 clude oui' 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. 



