his Lordship encouraged one, young both in years and in his profession, to meet and surmount the various obstacles and natural difficulties in the execution of this work, personal gratitude alone is due-but for the advantages derived from the bridge itself, the Earl of Morley has laid the public of Plymouth under lasting obligation.

The benefits to a nation, from such a spirit of truly patriotic liberality amongst her nobility, are incalculable. To the many magnificent exertions of it, England owes no small part of her commercial prosperity; and the names of the Dukes of Bridgewater, of Portland, &c. &c. should be venerated by every lover of his country, as powerful contributors to its present eminence. With regard to Plymouth, it is to be hoped that the example set by the noble Earl in this and other public works in the vicinity, may find imitators. The natural advantages of the town and port are great, and nothing appears to be wanting for raising them to a still higher scale of national importance, but a continuance of that enterprising and liberal spirit which is at present dawning amongst a large portion of the inhabitants.

Plymouth, Jan. 1829.

IV.

ON THE RISE AND DECLINE OF PARTICULAR MORTAL DISEASES, DURING THE LAST TWENTY-FIVE YEARS; WITH AN ATTEMPT TO ASCERTAIN THE LAW OF MORTALITY, IN RESPECT OF ITS DISTRIBUTION ON VARIOUS AGES, AND IN BOTH SEXES: BY EDWARD BLACKMORE, M. D. MEMBER OF THE ROYAL MEDICAL SOCIETY OF EDINBURGH, AND OF THE PLYMOUTH INSTITUTION.

Duntaxat Rerum Magnarum parva potest res
Exemplare dare, ac vestigia notitiaf.

LUCRETIUS.

THE subject of this paper is contained in the following passage of MALTHUS's Essay on the Principle of Population, vol. 2, B. iv. c. 5.-" Nature will not be defeated in her purposes; the necessary mortality must come in some form or other; and the extirpation of one disease will only be the signal for the birth of another, perhaps more fatal. We cannot lower the waters of misery by pressing them down in different places, which must necessarily make them rise somewhere else the only way in which we can hope to effect our purpose, is by drawing them off. In a country which keeps its population at a certain standard, if the average number of marriages and births be given, it is evident that the average number of deaths will be also given; and the channel through which the great stream of mortality is constantly flowing, will

always carry off a given quantity. Now if we stop up any of the given channels, it is most perfectly clear that the stream must run with greater force through some of the other channels; that is, if we eradicate some diseases, others will become more fatal. In this case, the only distinguishable cause is the damming up a necessary outlet of mortality. The way in which it operates, is probably by increasing poverty, in consequence of a supply of labour too rapid for the demand. If the cowpock should extirpate the small-pox, and yet the number of marriages continue the same, we shall find a very perceptible difference in the increased mortality of some other disease. Nothing could prevent this but a start in agriculture."The view of the reign of death herein exhibited, is truly dark and startling. This doctrine of the constancy of mortality wears an aspect which is naturally calculated to repress the efforts of philanthrophists to extirpate diseases;-and the fatalism with which it invests mortality, tends to shut up mankind in hopeless subjection to the various ills of their condition. The passage moreover assumes, that mortal diseases will necessarily and perpetually exist; and thus for ever precludes the hope of man's attaining to a natural issue of his earthly existence in the exhaustion of mature old age.— Omitting to discuss the truth of this proposition in the abstract, as designating the law of mortality in a state of society where the population is making pressure on the means of subsistence, I propose to inquire How far, from the register of deaths in the course of the last twenty-five years, mortality is shewn to be a constant quantity ?-What changes have been wrought in the various channels through which the great stream of mortality has been flowing-What relative proportion is observable in the rise and fall of particular diseases?— Has, for example, the depression in the mortality of the SMALLPOX since the discovery of the cow-POCK, been a means of diminishing the general mortality in the rate of that depression; or, has an increase in the mortality of some other diseases, absorbed those whom the decline of the small-pox had permitted

to survive? Can any natural explanation be assigned of the variations in the channels of mortality, and of the general constancy of death? or, is its invariable amount to be ascribed to an inscrutable law of Divine Providence !-"that," in the words of Dr. Woollcombe," which the plan of Providence in the creation of life requires ?" If there be such a determinate rule in the prevalence of death as Malthus expounds, what can MEDICINE effect in promoting the well being and life of the community?

The LONDON BILLS OF MORTALITY present us with the largest scale of deaths of any record within our reach; and they are of sufficient accuracy for the object of our inquiry. For although the designation of diseases in them is not scientific, and their materials are drawn from sources which might be presumed to be uncertain and inadequate; yet, as Dr. HEBERDEN has well remarked, "The agreement of the bills with each other at various periods, 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." And more exact proof of their general accuracy is to be found in the accordance of the numbers of those diseases, taken together, which are known to be peculiarly prevalent at particular ages, with the total numbers which were ascertained to have died at those very ages. It is only necessary to premise further, that THE BILLS' consist of two tables; one of the deaths at different ages, without distinguishing the fatal disease; the other of different diseases, without distinction of the particular ages, when they were severally fatal.

I select then, as proper tables for comparison, the BILLS for two periods of six years each, from 1795 to 1800 inclusive; and from 1820 to 1825 inclusive for the proportion of one mortal disease to the total mortality in any given period, is assumed to be a fair subject of comparison with the proportion