been little variation since the origin of the bills, would consequently be reformed; and we should then derive from them the elucidation of many important and dubious medical points, as 1. _The causes of many diseases, and their affinity to one another._ 2. _The rise, situation, increase, decrease, and cessation of epidemic and contagious diseases._ 3. _The means of guarding against their extension and effects._ 4. _The comparative healthiness of different countries and places, climates, and seasons._ 5. _The influence of particular trades and manufactures on the human constitution._ Such are the medical advantages which would arise from correct and enlarged bills of mortality. Dr. William _Heberden_[225] has made the following observations upon this subject: “People have fallen into two opposite errors concerning the Bills of Mortality; some have considered their authority as too vague to be made the foundation of any certain conclusions; and others have built upon this foundation, without sufficiently considering its real defects. Both parties are equally wrong. The agreement of the bills with each other does alone carry with it a strong proof that the numbers under the several articles are by no means set down at random, but must be taken from the uniform operation of some permanent cause. While the gradual changes they exhibit in particular diseases, correspond to the alterations which in time are known to take place in the channels through which the great stream of mortality is constantly flowing. That there are, however, many and very great imperfections in these bills cannot be doubted; for, _First_, the births include only those who are baptized according to the rites of the church of England, by which means all Jews, Quakers, and the very numerous body of dissenters are omitted. _Secondly_, of those who are of the church of England, a very large proportion are either buried in the country, or in burial grounds adjacent to London, but without the bills; the burials also in St. Paul’s Cathedral, in Westminster Abbey, the Temple, the Rolls, Lincoln’s Inn, St. Peters in the Tower, the Charter-house, the several hospitals of the metropolis, and other places which are not parochial cemeteries, are for that reason omitted; besides which, the great parishes of Mary-le-bone, and Pancras, have never yet had a place in the bills of mortality. _Thirdly_, many abortives and still-born are noticed in the deaths, but not in the births.” Dr. _Heberden_ proceeds to examine the fluctuation observable in certain diseases, and which he considers under two distinct points of view; the first comprehending their variations in different years; the second those which take place in different parts of the same year; we must refer the reader for much curious matter, and useful information, to his work above cited. Many of the provincial bills of mortality are more perfect than those of London, a superiority