CHAP. XIX. CONSTRUCTION OF THE TUBES. 



431 



CONSTRUCTION OF MAIN BRITANNIA TUBE ON THE STAGING. 



the mode of floating and raising them, were nearly the 

 same as at the Britannia Bridge, though the general 

 arrangement of the plates is in many respects different. 



It was determined to construct, the shorter outer .tubes 

 of the Britannia Bridge on scaffoldings in the positions 

 in which they were permanently to remain, and to erect 

 the larger tubes upon wooden platforms at high-water- 

 mark on the Caernarvon shore, from whence they were 

 to be floated in pontoons, in like manner as Eennie had 

 floated into their places the centerings of his Waterloo 

 and other bridges, and then raised into their proper 

 places by means of hydraulic power, after a method ori- 

 ginally suggested by Mr. Edwin Clark, to whose valuable 



