On the other hand, we have now a scientific doctrine of the effects of great fluctuations of the ground-water upon the production of telluric miasmata, which may be used to rationalize the theory of emanations adopted by Sydenham and Boyle. From this modern point of view the remarkable droughts preceding the pestilential fevers and plagues of 1624-25 and 1665, and preceding the fever of 1685-86, which is the one that immediately concerns us, may be not without significance. The London fever of 1685-86 having been suspected at the time to be the forerunner of a plague, as other such fevers in the earlier part of the century had been, and no plague having ensued, the question arises most naturally at this stage, why the plague should have never come back in London or elsewhere in Britain after the great outbreak of 1665-66. The extinction of Plague in Britain. Plague had been the grand infective disease of Britain from the year of the Black Death, 1348-9, for more than three centuries, down to 1666. The last of plague in Scotland was in 1647-8, in the west and north-west of England about 1650 (in Wales probably in 1636-8), in Ireland in 1650, and in all other parts of the kingdom including London in 1666, the absolute last of its provincial prevalence having been at Peterborough in the first months of 1667[53], while two or three occasional deaths continued to occur annually in London down to 1679. False reports of plague, contradicted by public advertisement, were circulated for Bath in 1675[54], and for Newcastle in 1710[55]; while in London as late as 1799, during a bad time of typhus fever, the occurrence of plague was alleged[56]. It is not easy to say why the plague should have died out. It had been continuous in England from 1348, at first in general epidemics, all over the country in certain years, thereafter mostly in the towns, either in great explosions at long intervals or at a moderate level for years together. The final outburst in 1665, which was one of the most severe in its whole history, had followed an unusually long period of freedom from plague in London, and was followed, as it were, by a still longer period of freedom until at last it could be said that the plague was extinct. In some large towns it had been extinct, as the event showed, at a much earlier date; thus at York the last known epidemic was in 1604, and it can hardly be doubted that many other towns in England, Scotland and Ireland would have closed their records of plague earlier than they did had not the sieges and military occupations of the Civil Wars given especial occasion for the seeds of the infection to spring into life. Plague seemed to be dying out all over England and Scotland (in Ireland it is little heard of except in connexion with the Elizabethan and Cromwellian conquests) for some time before its final grand explosion in London in 1665.