It would be impossible to describe in detail all the engineering works which are to be found on Mr. Brunel’s railways, the aggregate length of which is upwards of 1,200 miles; but in this chapter it is proposed to give a brief sketch of the lines he constructed, omitting all that can be more properly inserted in the three chapters which follow, relating to the broad gauge, to the Atmospheric System, and to the bridges and viaducts. * * * * * The Great Western Railway was opened to Maidenhead, a distance of nearly twenty-three miles, in June 1838, and to Twyford, eight miles farther on, in July 1839. A description of the Wharncliffe Viaduct at Hanwell will be found at p. 172, and of the Maidenhead bridge at p. 173. The line from Twyford to Reading was opened in March 1840, and from Reading to Chippenham by May 1841. Meanwhile the portion from Bristol to Bath had been opened in August 1840. The last division, namely, that from Chippenham to Bath, containing the Box Tunnel, was opened on June 30, 1841; and the railway was completed throughout its whole length. * * * * * A considerable part of the history of the Great Western Railway is connected with the adoption on it of the broad, or 7-foot gauge, and will be dealt with in the next chapter, in which is also given some account of the longitudinal system of permanent way. The bridges are described in Chapter VII.; but some of the other works may be noticed here. In laying out the line, Mr. Brunel endeavoured to make it as straight and as level as possible throughout, and to concentrate those changes of level, which could not be avoided, into short inclines, to be worked, if necessary, by auxiliary power. Accordingly the line is thus divided:-- Miles Yards Level, or with an inclination not exceeding 4 feet in the mile 67 88 Above 4 feet, and not exceeding 8 feet in the mile 47 110 Steep inclines 3 1210 The steep inclines are two in number, of a gradient of 1 in 100, or about 53 feet in a mile, and descend towards the Bristol end of the line. The Wootton Basset incline, 85½ miles from London, is 1 mile 550 yards long. The second incline is at Box, 99 miles from London, and is 2 miles 660 yards in length. An assistant engine is still occasionally used to work heavy trains at this point. On this incline the line passes through the Box Tunnel. This tunnel is the first out of London, and could only have been dispensed with by taking a circuitous route several miles longer than that adopted by Mr. Brunel. The tunnel is 1⅞ mile in length, and is ventilated by six shafts. They are 30 feet in diameter, and from 70 to 300 feet deep.