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construction。 The navigations brought lime； coal； manure； and
merchandise； almost to the farmers' doors； and provided them at the
same time with ready means of conveyance for their produce to good
markets。 Farms in remote situations were thus placed more on an
equality with those in the neighbourhood of large towns； rents rose
in consequence； and the owners of land everywhere became the
advocates and projectors of canals。
The dividends paid by the first companies were very high； and it
was well known that the Duke's property was bringing him in immense
wealth。 There was； therefore； no difficulty in getting the shares
in new projects readily subscribed for： indeed Mr。 Telford relates
that at the first meeting of the Ellesmere projectors； so eager
were the public； that four times the estimated expense was
subscribed without hesitation。 Yet this navigation passed through
a difficult country； necessarily involving very costly works； and
as the district was but thinly inhabited； it did not present a very
inviting prospect of dividends。*＇1＇ But the mania had fairly set
in； and it was determined that the canal should be made。 And
whether the investment repaid the immediate proprietors or not； it
unquestionably proved of immense advantage to the population of the
districts through which it passed； and contributed to enhance the
value of most of the adjoining property。
The Act authorising the construction of the canal was obtained in
1793； and Telford commenced operations very shortly after his
appointment in October of the same year。 His first business was to
go carefully over the whole of the proposed line； and make a careful
working survey； settling the levels of the different lengths；
and the position of the locks； embankments； cuttings； and aqueducts。
In all matters of masonry work he felt himself master of the
necessary details； but having had comparatively small experience of
earthwork； and none of canal…making； he determined to take the
advice of Mr。 William Jessop on that part of the subject； and he
cordially acknowledges the obligations he was under to that eminent
engineer for the kind assistance which he received from him on many
occasions。
The heaviest and most important part of the undertaking was in
carrying the canal through the rugged country between the rivers
Dee and Ceriog； in the vale of Llangollen。 From Nantwich to
Whitchurch the distance is 16 miles； and the rise 132 feet；
involving nineteen locks； and from thence to Ellesmere； Chirk；
Pont…Cysylltau； and the river Dee； 1 3/4 mile above Llangollen； the
distance is 38 1/4 miles； and the rise 13 feet； involving only two
locks。 The latter part of the undertaking presented the greatest
difficulties； as； in order to avoid the expense of constructing
numerous locks； which would also involve serious delay and heavy
expense in working the navigation； it became necessary to contrive
means for carrying the canal on the same level from one side of the
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 direc