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respective valleys of the Dee and the Ceriog to the other； and
hence the magnificent aqueducts of Chirk and Pont…Cysylltau；
characterised by Phillips as 〃among the boldest efforts of human
invention in modem times。〃*＇2＇ The Chirk Aqueduct carries the canal
across the valley of the Ceriog； between Chirk Castle and the
village of that name。 At this point the valley is above 700 feet
wide； the banks are steep； with a flat alluvial meadow between
them； through which the river flows。 The country is finely
wooded。 Chirk Castle stands on an eminence on its western side；
with the Welsh mountains and Glen Ceriog as a background； the whole
composing a landscape of great beauty； in the centre of which
Telford's aqueduct forms a highly picturesque object。
＇Image＇ Chirk Aqueduct
The aqueduct consists of ten arches of 40 feet span each。
The level of the water in the canal is 65 feet above the meadow；
and 70 feet above the level of the river Ceriog。 The proportions
of this work far exceeded everything of the kind that had up to
that time been attempted in England。 It was a very costly structure；
but Telford； like Brindley； thought it better to incur a considerable
capital outlay in maintaining the uniform level of the canal； than
to raise and lower it up and down the sides of the valley by locks
at a heavy expense in works； and a still 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 profession 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 hollow； with cross walls。 The spandrels
also； above the springing of the arches； were constructed with
longitudinal walls； and left hollow。*＇3＇ 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 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 otherwhich would
have involved seven or eight locks on each sideor 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 have involved a great waste of water； which was a
serious objection； 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 Telford 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
expensive。 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 larger scale。
＇Image＇ Pont…CyslltauSide view of Cast Iron Trough
It will be understood that many years elapsed between the period at
which Telford was appointed engineer to the Ellesmere Canal and the
designing of these gigantic works。 He had in the meantime been
carefully gathering experience from a variety of similar
undertakings on which he was employed； and bringing his
observations of the strength of materials and the different forms
of construction to bear upon the plans under his consideration for
the great aqueducts of Chirk and Pont…Cysylltau。 In 1795 he was
appointed engineer to the Shrewsbury Canal； which extends from that
town to the collieries and ironworks in the neighbourhood of
Wrekin； crossing the rivers Roden and Tern； and Ketley Brook； after
which it joins the Dorrington and Shropshire Canals。 Writing to his
Eskdale friend； Telford said ： 〃Although this canal is only
eighteen miles long； yet there are many important works in its
courseseveral locks； a tunnel about half a mile long； and two
aqueducts。 For the most considerable of these last； I have just
recommended an aqueduct of iron。 It has been approved； and will be
executed under my direction； upon a principle entirely new； and
which I am endeavouring to establish with regard to the application
of iron。〃*＇4＇
It was the same principle which he applied to the great aqueducts
of the Ellesmere Canal now under consideration。 He had a model made
of part of the proposed aqueduct for Pont…Cysylltau； showing the
piers； ribs； towing…path； and side railing； with a cast iron trough
for the canal。 The model being approved； the design was completed；
the ironwork was ordered for the summit； and the masonry of the
piers then proceeded。 The foundation…stone was laid on the 25th
July； 1795； by Richard Myddelton； Esq。； of Chirk Castle； M。P。； and
the work was not finished until the year 1803；thus occupying a
period of nearly eight years in construction。
The aqueduct is approached on the south side by an embankment 1500
feet in length； extending from the level of the water…way in the
canal until its perpendicular height at the 〃tip〃 is 97 feet；
thence it is carried to the opposite side of the valley； over the
river Dee； upon piers supporting nineteen arches； extending to the
length of 1007 feet。 The height of the piers above low water in the
river is 121 feet。 The lower part of each was built solid for 70
feet； all above being hollow； for the purpose of saving masonry as
well as ensuring good workmanship。 The outer walls of the hollow
portion are only two feet thick； with cross inner walls。 As each
stone was exposed to inspection； and as both Telford and his
confidential foreman； Matthew Davidson；*＇5＇ kept a vigilant eye
upon the work； scamping was rendered impossible； and a first…rate
piece of masonry was the result。
＇Image＇ Pont…Cyslltau Aqueduct
Upon the top of the masonry was set the cast iron trough for the
canal； with its towing…path and side…rails； all accurately fitted
and bolted together； forming a completely water…tight canal； with a
water…way of 11 feet 10 inches； of which the towing…path； standing
upon iron pillars rising from the bed of the canal； occupied 4 feet
8 inches； leaving a space of 7 feet 2 inches for the boat。*＇6＇
The whole cost of this part of the canal was 47；018L。； which was
considered by Telford a moderate sum compared with what it must
have cost if executed after the ordinary manner。 The aqueduct was
formally opened for traffic in 1805。 〃And thus；〃 said Telford； 〃has
been added a striking feature to the beautiful vale of Llangollen；
where formerly was the fastness of Owen Glendower； but which； now
cleared of its entangled woods； contains a useful line of
intercourse between England and Ireland； and the water drawn from
the once sacred Devon furnishes the means of distributing
prosperity over the adjacent land of the Saxons。〃
＇Image＇ Section of Top of Pont…Cyslltau Aqueduct。
It is scarcely necessary to refer to the other works upon this
canal； some of which were of considerable magnitude； though they
may now seem dwarfed by comparison with the works of recent
engineers； Thus； there were two difficult tunnels cut through hard
rock； under the rugged ground which separates the valleys of the
Dee and the Ceriog。 One of these is 500 and the other 200 yards in
length。 To ensure a supply of water for the summit of the canal；
the lake called Bala Pool was dammed up by a regulating weir； and
by its means the water was drawn off at Llandisilio when required
for the purposes of the navigation； the navigable feeder being six
miles long； carried along the bank of the Llangollen valley。
All these works were skilfully executed； and when the undertaking
was finished； Mr。 Telford may be said to have fairly established
his reputation as an engineer of first rate ability。
We now return to Telford's personal history during this important
period of his career。 He had long promised himself a visit to his
dear Eskdale； and the many friends he had left there； but more
especially to see his infirm mother； who had descended far into the
vale of