Embankments.
10. Besides contending with water above ground as well as below, the constructor of a railway is occasionally assailed by an element of a very different nature. For instance, when the Wolverhampton embankment of the present London and North-Western Railway, at vast trouble and expense, was nearly finished, it was observed first to smoke, then get exceedingly hot, until a slow mouldering flame visible at night appeared. The bank began to consume away, and the heat continued until it actually burned the railway sleepers; at last, however, it exhausted itself. The combustion was caused by the quantity of sulphuret of iron or pyrites contained in the earth of the embankment, which, having been baked by the fire, will probably never slip.
11. It would be tedious, and indeed impossible, to detail the various works which a railway engineer has to superintend in the construction of the line, in the laying down of the rails or “permanent way,” and in the subsequent, or rather simultaneous, erection of the various station-houses, storehouses, workshops, &c. &c., the interior of which we shall soon have occasion to enter.
An idea, however, of the magnitude of his operations may be faintly imparted by the following brief abstract of a series of calculations made by Mr. Lecount, one of the engineers employed in the construction of the southern division of the present London and North-Western Railway, and the writer of the article ‘Railways’ in the ‘Encyclopædia Britannica.’ The great Pyramid of Egypt was, according to Diodorus Siculus, constructed by three hundred thousand—according to Herodotus by one hundred thousand—men; it required for its execution twenty years, and the labour expended on it has been estimated as equivalent to lifting 15,733,000,000 of cubic feet of stone one foot high. Now, if in the same manner the labour expended in constructing the Southern Division only of the present London and North-Western Railway be reduced to one common denomination, the result is 25,000,000,000 cubic feet of similar material lifted to the same height; being 9,267,000,000 of cubic feet more than was lifted for the pyramid; and yet the English work was performed by about 20,000 men only, in less than five years.
Again, it has been calculated by Mr. Lecount that the quantity of earth moved in the single division (112½ miles in length) of the railway in question would be sufficient to make a foot-path a foot high and a yard broad round the whole circumference of the earth! the cost of this division of the railway in penny-pieces being sufficient to form a copper kerb or edge to it. Supposing therefore the same proportionate quantity of earth to be moved in the 7150 miles of railway sanctioned by Parliament at the commencement of 1848 (Vide Parliamentary Returns), our engineers within about fifteen years would, in the construction of our railways alone, have removed earth sufficient to girdle the globe with a road one foot high and one hundred and ninety-one feet broad!
Abandoning, however, speculations of this nature, we will conclude our slight sketch of the principal works required for a railway by a few data, exemplifying the magnitude of the Britannia Bridge over the Menai Straits, the construction of which has been intrusted by its well-known inventor to the very able and experienced management of Mr. Frank Forster.
The dimensions of this straight wrought-iron aërial gallery, through which passengers and goods are to travel by rail, are—
| Total length of bridge, divided into 4 openings— | ⎫ | Feet. In. 1834 9 | |
| 2 of 230 feet | } each | ⎬ | |
| 2 of 460 feet | ⎭ | ||
| Height of rails above high-water mark | 104 0 | ||
| Quantity of masonry in the towers and abutments | { | 1,365,000 cubic feet. | |
| Weight of one of the iron tubes for the largest span, to be lifted 100 feet | } | 1,800 tons. | |
| Value of each of the largest of the iron tubes, notincluding expense of raising it | } | £54,000 | |
| The cost of the scaffolding now in use about thebridge has exceeded | } | £50,000 | |
It would, we conceive, be impertinent to dilute the above facts by a single comment.