CHAP. VI. WATEKLOO BRIDGE. 185 



fixed in a strong cast iron box firmly bedded in the solid 

 floor of the barge. The apparatus worked so well and 

 smoothly, that the whole centre, consisting of eight ribs, 

 each weighing about fifty tons, was usually placed within 

 the week. 



The means employed by Mr. Rennie for forming his 

 road upon the bridge were identical with those adopted 

 by Mr. Macadam at Bristol some six years later. But the 

 arrangement constituted so small a part of our engineer's 

 contrivances, that, as in many other cases, he made no 

 merit of it. When the clay puddle placed along the 

 intended roadway was sufficiently hard, he spread a 

 stratum of fine screened gravel or hoggins, which was 

 carefully levelled and pressed down upon the clay. This 

 was then covered over with a layer of equally broken 

 flints, about the size of an egg ; after which the whole 

 was rolled close together, and in a short time formed 

 an admirable " macadamized " road. Mr. Eennie had 

 practised the same method of making roads over his 

 bridges long before 1809 ; and he continued to adopt 

 it in all his subsequent structures. 



The whole of the stone required for the bridge 

 (excepting the balustrades, which were brought ready 

 worked from Aberdeen) was hewn in some fields ad- 

 jacent to the erection on the Surrey side. It was 

 transported on to the work upon trucks drawn along rail- 

 ways, in the first instance over temporary bridges of 

 wood ; and it is a remarkable circumstance that nearly 

 the whole of the material was drawn by one horse, 

 called " Old Jack" a most sensible animal, and a great 

 favourite. His driver was, generally speaking, a steady 

 and trustworthy man, though rather too fond of his dram 

 before breakfast. As the railway along which the stone 

 was drawn passed in front of the public-house door, the 

 horse and truck were usually pulled up while Tom 

 entered for his " morning." On one occasion the driver 

 stayed so long that "Old Jack," becoming impatient, 



