344 



CHIRK AQUEDUCT. 



PART VIII. 



greater cost in time and water. The aqueduct is a splendid 

 specimen of the finest class of masonry, and Telford 



showed himself a master of his pro- 

 fession by the manner in which he 

 carried out the whole details of 

 the undertaking. The piers were 

 carried up solid to a certain height, 

 above which they were built hol- 

 low, with cross walls. The span- 

 drels also, above the springing of 

 the arches, were constructed with 

 longitudinal walls, and left hol- 

 low. 1 The first stone was laid on 

 the 17th of June, 1796, and the 

 work was completed in the year 

 1801 ; the whole remaining in a 

 perfect state to this day. 



The other great aqueduct on 

 the Ellesmere Canal, named Pont-Cysylltau, is of even 



SECTION OF PIER. 



1 Telford himself thus modestly 

 describes the merit of this original 

 contrivance : " Previously to this time 

 such canal aqueducts had been uni- 

 formly made to retain the water ne- 

 cessary for navigation by means of 

 puddled earth retained by masonry ; 

 and in order to obtain sufficient 

 breadth for this superstructure, the 

 masonry of the piers, abutments, and 

 arches was of massive strength ; and 

 after all this expense, and every ima- 

 ginable precaution, the frosts, by 

 swelling the moist puddle, frequently 

 created fissures, which burst the ma- 

 sonry, and suffered the water to escape 

 nay, sometimes actually threw down 

 the aqueducts; instances of this kind 

 having occurred even in the works of 

 the justly celebrated Brindley. It 

 was evident that the increased pres- 

 sure of the puddled earth was the 

 chief cause of such failures : I there- 

 fore had recourse to the following 

 scheme in order to avoid using it. 

 The spandrels of the stone arches were 

 constructed with longitudinal walls, 



| instead of being filled in with earth 

 (as at Kirkcudbright Bridge), and 

 across these the canal bottom was 

 formed by cast iron plates at each 

 side, infixed in square stone masonry. 

 These bottom plates had flanehes on 

 their edges, and were secured by nuts 

 and screws at every juncture. The 

 sides of the canal were made water- 

 proof by ashlar masonry, backed 

 with hard burnt bricks laid in Parker's 

 cement, on the outside of which was 

 rubble stone work, like the rest of 

 the aqueduct. The towing path had 

 a thin bed of clay under the gravel, 

 and its outer edge was protected by 

 an iron railing. The width of the 

 water-way is 11 feet ; of the masonry 

 on each side, 5 feet 6 inches ; and the 

 depth of the water in the canal, 5 feet. 

 By this mode of construction the 

 quantity of masonry is much dimin- 

 ished, and the iron bottom plate forms 

 a continuous tie, preventing the side- 

 walls from separation by lateral pres- 

 sure of the contained water." ' Life 

 of Telford,' p. 40. 



