56 SMEATON'S EXTENSIVE EMPLOYMENT PART VI. 



head of the current under the other arches, which was 

 necessary for the purpose of driving the wheels by means 

 of which a considerable part of the water required for the 

 supply of the City was still raised. Mr. Smeaton's recom- 

 mendations were adopted as the most advisable course 

 to be pursued under the circumstances ; and horses, carts, 

 and barges were at once set to work, and the stones 

 were tumbled into the stream at the base of the tottering 

 piers. By these means the destruction of the foundations 

 was temporarily stayed, and the process of patching up 

 the old bridge went on from time to time for sixty 

 years more, until it was at length effectually remedied 

 by the erection of the present structure. 



In connection with the works at Old London Bridge, 

 Mr. Smeaton also furnished a design for a new pumping- 

 engine, which was placed in the fifth arch, and worked 

 by the rise and fall of the tide. Before the invention of 

 the steam-engine, this was an economical though an 

 irregular method of obtaining motive power. The same 

 tides that lifted great ships up the river and let them 

 down again twice in each day, then drove pumping- 

 engines and even flour-mills the driving-wheels turning 

 one way as the tide rose and another as it fell. 1 This 

 power was, however, shortly superseded by the still 

 more economical power of steam : for the steam-engine, 

 though involving a considerable expenditure of coal, 

 proved cheaper in the end, because it was so much 

 more certain, regular, and expeditious than the natural 

 power of the tides. 



The bridges erected after Mr. Smeaton's original de- 

 signs, were those of Perth, Coldstream, and Banff; the 

 only one which he erected in England being at Hex- 

 ham, in Northumberland, which proved a failure. He 

 was consulted about the new bridge at Perth as early as 

 the year 1763, when he visited the place, fixed upon the 

 best site for the structure, and afterwards furnished the 



1 ' Encyclopedia Metropolitana,' vol. vii., p. 139. 



