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.