42 Ihe Viagraph. 



a profile of the road-surface, and (2nd) indicating a numerical 

 index of the unevenness of the surface. These taken together 

 give a quite fair estimate of the quality of the road at the pait 

 tested. 



Fig. I gives a general view of the instrument, the frame of 

 which is in form like a sled, with straight runners. On this 

 are mounted the working parts shown in Fig. 2. The lever 

 T, pivoted to the main frame at H, carries on its free end a 

 serrated wheel, the upper part of which is seen at V. While 

 the main frame, in being drawn along the road, preserves a 

 sufficiently even line, the road wheel V rises and falls over all 

 the unevennesses of the surface, carrying with it the lever 

 T, and thereby transmitting its movements by means of the 

 hnk and lever S to the pencil P, which marks the full ampli- 

 tude of these motions on the paper passing round the drum 

 A. (In the figure this pencil- is raised above its usual position, 

 from the necessity of raismg the road-wheel V so as to bring 

 it into view.) While the motion of the pencil takts place in a 

 vertical direction, the paper on which it marks is carried under 

 it by the drum A, which is rotated by a worm and wheel below 

 it connected by a shaft and bevel gear with the road wheel V. 

 The paper is thus drawn from the stock-roll C, passed under 

 the pencil and wound up on the receiving-drum B. The 

 result is a profile of the road surface, of which the scale x^full 

 size vertically^ and |z«. to \ft. longitudinally. A second pencil 

 seen below P draws a datum line corresponding to that which 

 the indicating pencil P would produce from a perfectly even 

 road. From this can be measured the depths of the '' ruts ' or 

 " cups," or other unevennesses indicated on the diagram. The 

 sum of the depths of all these unevennesses constitutes the 

 numerical index of unevenness, and is indicated on the decimal 

 counter W, which is worked as follows : — A cord attached to 

 the free end of the lever T is passed once round the double- 

 grooved pulley X, and connected to the stretched rubber band 

 at O. When the lever T descends, owing to the fall of the 

 road-wheel V, into a rut or cup in the surface, this cord rotates 



