CHAP. VI. AQUEDUCT OF PONT-CYSYLLTAU. 345 



greater dimensions, and a far more striking object in 

 the landscape. Sir Walter Scott spoke of it to Southey 

 as " the most impressive work of art he had ever 

 seen." * It is situated about four miles to the north 

 of Chirk, at the crossing of the Dee, in the romantic 

 vale of Llangollen. The north bank of the river is 

 very abrupt ; but on the south side the acclivity is 

 more gradual. The lowest part of the valley in which 

 the river runs is 127 feet beneath the water-level of 

 the canal ; and it became a question with the engineer 

 whether the valley was to be crossed, as originally 

 intended, by locking down one side and up the other 

 which would have involved seven or eight locks on 

 each side or by carrying it directly across by means 

 of an aqueduct. The execution of the proposed locks 

 would have been very costly, and the working of them 

 in carrying on the navigation would necessarily involve 

 a great waste of water, which was a serious objec- 

 tion, inasmuch as the supply was estimated to be no 

 more than sufficient to provide for the unavoidable 

 lockage and leakage of the summit level. Hence Tel- 

 ford's opinion was strongly in favour of an aqueduct ; 

 but, as we have already seen in the case of that at 

 Chirk, the height of the work was such as to render 

 it impracticable to construct it in the usual manner, 

 upon masonry piers and arches of sufficient breadth and 

 strength to afford room for a puddled water-way, which 

 would have been extremely hazardous as well as expen- 

 sive. He was therefore under the necessity of contriving 

 some more safe and economical method of procedure ; and 

 he again resorted to the practice which he had adopted 

 in the construction of the Chirk Aqueduct, but on a much 

 more formidable scale. 



It will be understood that many years elapsed between 

 the period at which Telford was appointed engineer to 



Selections from the Letters of Southey, vol. iii., p. 502. 



