For the conduct of quarantine against the Baltic, the historian is lucky to have two detailed and complementary sources – one from the Privy Council, the other from the Treasury. They give largely the same information, gathered at different stages, but as neither source is comprehensive or wholly accurate in itself, one tends to correct the other or make up any shortfall. The position will be clearer once the procedures and processes of quarantine are explained. It should be understood that these steps represent the mature system, in the context of a ship not owned or freighted by a contractor to the Navy Board. That consideration does not affect the extent of the evidence (which shows liability to quarantine as well as its performance), but it does mean that some ships, as will be seen, escaped the worst of the rigmarole and expense.