The first masonry was laid on 12 January 1847. A temporary timber viaduct on the east side was ready on 20 August 1848.
Timber coffer dams were constructed; they were 76 ft 6 in (23.32 m) by 29 ft (8.8 m) with two skins, the space between being filled with puddle clay. James Nasmyth had a novel design of steam pile driver; it had first been used in Devonport Docks in 1845; it could deliver 60 to 70 blows a minute; the cycle time with the hand-operated pile drivers formerly in use was four minutes. The drop weight was 1½ tons and its stroke was 2 ft 9 in (0.84 m); one was purchased from Nasmyth.
The ground gave considerable trouble during construction; Stephenson recorded:
Many difficulties occurred in driving the piles which considerably retarded the progress of the work, and, among others, the peculiar effect of ebb and flow during this operation is worthy of note. At flood-tide, the sand became so hard as almost totally to resist the utmost efforts of driving, while at ebb the sand was quite loose, and allowed of doing so with facility. It was therefore found necessary to abandon the driving on many occasions during high water. The difference between high and low water is 11 feet 6 inches. Another difficulty arose from the quicksands beneath the foundations. Although the piles were driven to the rock bottom, the water forced its way up, baffling the attempts to fill in between them; this, however, was remedied by using a concrete made of broken stone and Roman cement, which was continually thrown in until the bottom was found to be secure.[10]
The arch ribs were erected in section by travelling crane; each arch was temporarily erected at the contractor’s works.[10] The first was placed on 10 July 1848, and the erection of the ironwork was quick.
Already on 29 August 1848, it was possible to pass a special train over the first arch, and over a temporary structure for the rest of the crossing:
The High Level Bridge Over the Tyne: This important junction between the York and Newcastle and the Newcastle and Berwick Railway has been completed, and the event was celebrated on Tuesday last. In the afternoon of that day, a train of [specially invited] passengers passed along the temporary timber viaduct from the station at Gateshead to the station at Newcastle. Mr Hudson and several other Directors of the York, Newcastle, and Berwick line, who had been visiting Sunderland ... proceeded in a special train from that town to Gateshead... Several carriages were then added to the special train, and an open truck placed at each end, in which bands of music were stationed. The shrill sound of the whistle gave the signal for a royal salute, under the booming of which the train passed along the line, the band playing, and the thousands assembled to witness the event, rending the air with joyous acclamation Upon reaching the bridge, the bands struck up the well-known local air of "The Keel Row" which they continued till the train had reached the solid ground on the northern side of the river... The train proceeded to the Newcastle and Berwick station, where the company alighted and walked in procession to the Queen’s Head Inn, where a magnificent entertainment had been provided for the Directors and their friends, by the Mayor of Newcastle.
[From the south abutment of the High Level Bridge] and the river pier on the south side, the cast iron arch and road-way are nearly completed, and the second arch will be in progress in the course of a few weeks. From the middle of the first arch, the line curves to a temporary timber viaduct erected along the west side of the intended bridge. The height of this viaduct is one hundred and twenty feet to the level of the rails; it is built upon piles, which are driven between thirty and forty feet into the bed of the river. Its stability was sufficiently tested on Monday, when Captain Leffan (sic), the Government Inspector of Railways, examined it preparatory to the opening. On that day, two powerful engines weighing upwards of seventy tons, traversed it at different degrees of speed for between two and three hours; the weight would be about one ton to a foot, being four or five times greater than the temporary structure will ever be required to bear, and the result was, in the highest degree, satisfactory.
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