Soon after the capture, the detachment of the sixth and seventh companies, first battalion, returned to Cadiz, Major-General Cooke having represented the desirableness of maintaining the corps in adequate strength to carry out the defensive operations under his orders.[187] The sixth of the second battalion was attached to the expedition for besieging Tarragona,[188] and portions of the fifth and seventh companies, second battalion, remained at Badajoz to assist in the repairs of the breaches, and in improving the defences of the town. One private was killed by the unexpected explosion of a blast when he applied the match to fire it. The restorations were effected before the close of the year, and to mark the date, some masons of the corps built the number of the year with 24-pound shot in the escarp wall of the face of the bastion La Trinidad. ----- Footnote 187: Ibid, v., p. 650. Footnote 188: In the Dispatch to the Earl of Liverpool, dated Fuente Guinaldo, 10th June, 1812, the Earl of Wellington states, “I have likewise sent from this country to Gibraltar Lieutenant-Colonel Jones and four subaltern officers of engineers, and two companies of military artificers, including all the sappers there are with the army,” to join the corps d’armée under Lieutenant-General Lord William Bentinck, “to make an attack on the eastern coast of the Peninsula, with the troops from Sicily.”—Wellington Dispatches; 1845, v., p. 706, 707. The above company, 92 strong, was the only one despatched from Portugal, but one of the Maltese military artificers from Messina was added to the engineers' means for the siege, which made a combined sapper-force of 134 strong. ----- The bridges of Yecla and Serrada, which spanned the Yebra—a branch of the Douro between Salamanca and Cuidad Rodrigo—were mined in December 1811 by Spanish miners, with a few privates of the sappers as overseers, under the direction of Lieutenant W. Reid, royal engineers. Owing to the flinty nature of the cement giving the compactness of rock to the structures, it required a fortnight’s unceasing toil—day and night—to drive the shafts. The mines were fired in April, following, when one arch of the Yecla was blown down, and a pier and two arches of the Serrada were destroyed. Sub-Lieutenant C. Booth and ninety-five men reinforced the companies in Spain under Sir Richard Fletcher. Nine men also joined from Madeira. Both parties landed in April increasing the artificer force to 273 of all ranks. All the effective men were attached to the different divisions of the army, or were dispersed on various duties throughout the country. Those remaining at Badajoz were instructed in sapping and mining under Lieutenant Harry Jones of the royal engineers.