63 



Later in the season a sample of the Haider Patent Concrete Pave- 

 ment was laid on the Drive. This also promises well, but time and 

 the elements must decide the merits of this or of the Scharf Pavement. 

 The sample of Fisk concrete laid in 1867 was almost entirely disinte- 

 grated last season, and during the past summer the patentees, at their 

 own cost, re-surfaced it, but before the season was over it had again 

 gone to pieces. For Avalks it answers a better purpose, but even for 

 walks the sierns of failure are at this time becomiuo- evident. The dis- 

 integration commences at the bottom and gradually comes to the sur- 

 face. 



STEAM ROAD ROLLER, 



During the season the Park Commission authorized the purchase of 

 a Steam Road Roller from Messrs. Aveling & Porter, of Liverpool. 

 England. It arrived in the Park in August, and was immediately set 

 up by Park employees, and put to work, and from that time until the 

 work upon the drives was suspended for the season, it worked almost 

 constantly, and, for a great portion of the time, night and day. It 

 effected a very marked saving in the expense of rolling. The roller 

 weighs fifteen tons, and rolls a width of six feet. It moves either 

 backward or forward with equal facility, and hence does not have to be 

 turned around on the drive, although it can be turned around in its 

 own length, which is about twenty feet. The rollers are five feet in 

 diameter. Although this roller may be entirely adapted to the rolling 

 of broken stone or McAdam roads, a few modifications could be made 

 which would improve it for rolling gravel roads. The rollers should 

 be at least six feet in diameter, so that they would not have so great a 

 tendency to roll the gravel up in waves before them. Secondly, the 

 face of the roller should be straight. On this one the rollers are about 

 five-eighths of an inch convex, and there being four of them, the effect 

 is to produce four parallel depressions, five-eights of an inch deep, and 

 this is only produced by moving the gravel sidewise. This sidewise 

 motion is prejudicial to the packing, and would be obviated by making 

 the faces of the rollers straight, instead of convex. Again, for soft 

 roads, Park roads, with a layer of fresh gravel, three or four inches 

 thick upon them, the traction power of this roller is scarcely sufficient. 

 This could be obviated, either by coupling the four rollers, so that they 

 would all become driving wheels, or else by throwing more weight 

 upon the driving wheels. The roller, as it is, effects a very great 

 saving of expense in rolling, but the above obvious improvements 

 would add considerably to its efficiency. The cost of running it is 

 about ten dollars per day, and it does about twice as much effective 

 rolling as the seven ton Park roller, which required eight horses to run 

 it, and costs twenty dollars per day. 



