Forced labour such as this could of course only be applied to works where skilled artificers were not necessary; but occasions soon multiplied when the town mob had to be replaced by trained labourers, and we already see traces of a transitional system in the making of the Hythe harbour, where the municipality had to engage hired labour for such work as could not be done by the burgesses.[259] But undertakings for which scientific skill was needed sorely taxed local resources, and the burghers were driven to make anxious appeals to public charity. In 1447, when Bridport wanted to improve its harbour, collectors were sent all over the country to beg for money; indulgences of forty or a hundred days were promised to subscribers by archbishops and bishops; and a copy of the paper carried by one of the collectors gives the sum of the masses said for them in the year as amounting to nearly four thousand: “the sum of all other good prayers no man knoweth save only God alone.”[260] The building and repairing of bridges as being also work that demanded science and skilled labour involved serious cost. When the King had allowed the bridge at Nottingham to fall into the river, he generously transferred its ownership and the duty of setting it up again to the townspeople; who appointed wardens and kept elaborate accounts and bore grievous anxiety, till finding its charges worse than all their ordinary town expenses they at last fell to begging also. So also the mayor of Exeter prayed for help in the matter of the bridge there, which had been built by a wealthy mayor and was “of the length or nigh by, and of the same mason work as London Bridge, housing upon except; the which bridge openly is known the greatest costly work and most of alms-deeds to help it in all the west part of England.”[261] Such instances reveal to us the persistent difficulties that beset a world where primitive methods utterly failed to meet new exigencies, and where the demand for technical quality in work was beginning to lead to new organizations of labour. Meanwhile the burghers had to fight their own way with no hope of grants in aid from the state, and little to depend on save the personal effort of the whole commonalty.