seamen; with boys as young as 14 going off to sea. The other men obtained unskilled work on the waterfront as dockers, carters and coal heavers. By this time there were 3,100 dock labourers, 2,000 of whom were casual workers or "spellsmen" hired on a daily basis at low pay. Whilst Protestants and Catholics held the same jobs, the sectarian attitudes which dominated every aspect of life in Belfast ensured that Protestant dockers worked in the cross-channel docks where employment was more regular whilst Catholic dockers were made to work in the more dangerous deep sea docks, where the casualty rate was the highest. They were also the first to be laid off when labour cutbacks were required. Author John Gray in his book, City in Revolt: James Larkin and the Belfast Dock Strike of 1907 described the differences in wages earnings and the standard of living between the skilled and unskilled workers as "a yawning abyss, unequalled anywhere else in the United Kingdom". It was into this environment and social milieu that trade union leader James Larkin (a Liverpool-born Irish Catholic) arrived in January 1907. He was sent to Belfast by James Sexton, head of the National Union of Dock Labourers (NUDL), with the aim of bringing the dock workers and carters into the union. Addressing crowds of people on the steps of Belfast's Custom House, he vociferously articulated the grievances of the working classes. Due to his charismatic personality and considerable oratorial skill, Larkin succeeded in unionising the unskilled Protestant and Catholic workers. The lockout By April 1907, Larkin had recruited 2,000 workers into the NUDL union; in May the number had reached 4,500. The massive wave of labour strikes which would bring chaos to Belfast throughout the summer commenced on 26 April at Samuel Davidson's Sirocco Engineering Works in East Belfast with a walk-out by non-union workers demanding higher wages. The union members amongst Sirocco's employees were promptly sacked and the rest of the workers were each obliged to sign a document pledging not to join a trade union. The next strike occurred on Queen's Quay by employees of the coal merchant Samuel Kelly. This was after he had dismissed union members from his workforce and Larkin called for the rest of the coal workers to go on strike. On 6 May, dockers working on the SS Optic owned by Belfast Steamship Company also went out on