At the age of twenty-three Telford at length quitted Eskdale, and visited Edinburgh with a view to obtain better employment. The splendid improvements then in progress in that city enlarged his field of observation, and enabled him to contemplate architecture as applied to the object of magnificence as well as utility; and he seems at this time to have devoted much attention both to the scientific study of architecture and to drawing.
After remaining in Edinburgh two years, he removed to London, where he obtained employment upon the quadrangle of Somerset House, then erecting by Sir William Chambers, an engagement in which he states that he obtained much practical information.
After this, in 1784, he was engaged to superintend the erection of a house for the resident commissioner at Portsmouth Dockyard, and for the next three years was occupied upon various buildings in this dockyard, which gave him good opportunities of becoming well acquainted with the construction of graving-docks, wharf walls, and other similar engineering works. Two or three years previous to this, Telford's good character and promising talent had secured for him the friendship of two families resident in his native district,—the Pasleys and the Johnstones,—and to their influence his early employment on important works is in some measure to be attributed.
In 1787, having completed his engagements at Portsmouth, he was invited by Sir William Pulteney (a member of the Johnstone family) to take the superintendence of some alterations to be made in Shrewsbury Castle. Telford consequently removed to Shrewsbury, where he was employed to erect a new jail, completed in 1793, and was afterwards appointed county surveyor, in which office (retained by him until death) he had to design, and oversee the construction of, bridges and similar works. The first bridge which he designed and built was that over the Severn at Mont-fort, consisting of three elliptical stone arches, one of fifty-eight, and the others of fifty-five feet span. His next was the iron bridge over the Severn at Buildwas, which was the third iron bridge ever erected in Great Britain, the first being the Colebrookdale in Shropshire, built in the years 1777-9, and the second the Wearmouth,[38] erected between the years 1793-6. Telford's bridge over the Severn was erected in 1796, and consisted of a single arch of 130 feet span, formed of five cast iron ribs, and having a rise of only 14 feet; the width of the platform is 18 feet, and the total weight of iron in the bridge about 174 tons; it was constructed by the Coalbrookdale Ironmasters at a cost of 6,034l. Forty smaller bridges were erected in Shropshire under Telford's direction.
The first great undertaking, upon which Mr. Telford (in conjunction with Mr. Jessop) was engaged, was the Ellesmere Canal, a series of navigations intended to unite the Severn, the Dee, and the Mersey, and extending altogether to a length of nearly one hundred and twenty miles. From the date of this engagement, about 1793, Telford directed his attention almost entirely to civil engineering. In the execution of the immense aqueducts, required on this work, which cross the valleys of the Ceroig or Chirk, and of the Dee, at an elevation of 70 and 120 feet respectively, cast iron was first introduced as a material for forming the water-troughs of the canal, in place of the usual puddled clay confined in masonry, a practice which involved great expense, and some danger in times of frost, from the expansion of the moist clay. In the locks of this canal Telford also introduced cast iron framing in place of timber; and in one instance, where the lock was formed in a quicksand, he made every part of the above material.
The Caledonian Canal, of which Mr. Jessop was consulting engineer, was another of Mr. Telford's principal works. This canal was opened throughout its course in the year 1823, and it forms a noble monument of the skill of the engineer. The locks are stated by Telford to be the largest ever constructed at that time, being 40 feet wide, and from 170 to 180 feet long. Of other canals constructed wholly or partially under his superintendance, it is sufficient to mention the Glasgow, Paisley, and Androssan; the Macclesfield; the Birmingham and Liverpool Junction; the Gloucester and Berkeley; the Birmingham, which was completely remodelled by him and adapted to the conduct of a very extensive traffic, and the Weaver navigation in Cheshire. On the Continent he likewise superintended the construction of the Gotha Canal in Sweden, a navigation of about 125 English miles, of which 55 are artificial canal. From the Lake Wener at one extremity, this navigation rises 162 feet to the summit level, and falls 370 feet to the Baltic at the other; the rise and fall are effected by fifty-six locks, and the canal is 42 feet wide at the bottom and 10 feet deep. Upon its completion Telford received a Swedish order of knighthood, and as a farther mark of the royal approbation, received the King of Sweden's portrait set in diamonds.
The works executed by Telford under the Commissioners of Highland Roads and Bridges are of great importance. The practical operations under this commission, appointed in 1803, embraced about a thousand miles of new road, with nearly 1,200 new bridges, which caused the whole of Scotland, from its southern boundary near Carlisle, to the northern extremity of Caithness, and from Aberdeenshire on the east, to the Argyleshire islands on the west, to be intersected by roads; and its largest rivers and even inferior streams to be crossed by bridges. The execution of this undertaking occupied a period of twenty-five years, and all was done under the sole direction of Telford. The great road from London to Holyhead remains, perhaps, one of the most perfect specimens of his skill as an engineer; the improvements in it were executed by him, under another Parliamentary Commission appointed in 1815, and Telford himself appears to have regarded this work with peculiar satisfaction.
The Menai suspension bridge is, however, unquestionably one of the noblest monuments of Mr. Telford's fame, and it may be said to have inaugurated the era of the extensive introduction of wrought iron into great permanent structures exposed to heavy strains.[39] This bridge was commenced in 1819, and opened for traffic in 1826. The distance between the two piers is 550 feet, and the whole roadway, which is carried over four arches on the one side, and three on the other, has a length of 1000 feet, and a breadth of 30 feet. The total cost of the work was 120,000l.
Mr. Telford also built many other bridges of considerable size, and executed some important harbour works at Aberdeen and Dundee; but his most striking performance of this latter class is the St. Katharine Docks, London. One of his latest engagements was the survey of Dover harbour, undertaken in January, 1834, at the request of the Duke of Wellington, (as Warden of the Cinque Ports,) with a view to the adoption of measures to check the accumulation of shingle at the entrance.
During the course of his life Mr. Telford taught himself Latin, French, and German, so as to be able to read those languages with fluency, and to be able to converse freely in French. He is likewise said to have been well acquainted with algebra, but to have placed more reliance upon experiment, than on mathematical investigation. He contributed to the 'Edinburgh Encyclopædia' the articles—'Architecture,' 'Bridge Building,' and 'Canal Making.' Besides the above, he wrote an account of his own life, giving elaborate descriptions of his various professional undertakings. (Life of Thomas Telford, written by himself. Edited by John Rickman. London, 1833, 4to.)