same distinction should be found in the statement of the age at which the mortality occurred. These elements of Sex and Race and Age are, as far as our present knowledge goes, in nowise correlatives; they are entirely independent.

In this state of documentary information, I am compelled then to resort to artificial methods for deducing the factor desired; which are at best but a partial substitute for direct ones; and whose result, only theoretically accurate in the case of a stationary population, (i. e. where the births and deaths annually are equal) is but approximate here. This, however, is not the only instance in physics or metaphysics where we have to be content with approximations

The first step, then, is to ascertain the average proportionate mortality corresponding to each given age. For this, I have arranged the years in the same groupes as just now, and have indicated the average absolute and comparative results in the following

Table shewing the average Annual Mortality and its proportion for different ages, at several periods.

The latter columns of this table shew how the increased mortality of the last six years, which we have already had occasion to notice, has been distributed; it has fallen altogether upon the period before and about puberty. From the age of 21 years and upwards, the mortality has been sensibly diminished. I shall not stop now to comment upon this fact, that the stress of mortality is bearing with progressive force upon our indigenous population.

The proportion of still-born infants to the unitary mortality, assuming that to be the equivalent of the births, is, if we take the mean, above what has been recognized for European cities; as will appear by the following statement:

This last number, however, to be reliable, should be derived from a register of actual births. I may add that the proportion in this respect, usually accepted among statists, is for cities,

and for rural districts,

1 in 18; 1 in 30.

This disparity has been attributed by some to the compliance of females during gestation to one of the prejudicial fashions in cities-tight lacing. No doubt this is one particular, among many others that could be enumerated, by which the general habit of life in the country is more favorable to a robust and healthy developement, than in towns. A more important element of the present disparity, however, appears in the difference of numbers in the illegitimate births in town and in country, and the greater liability of illegitimates to be still-born. In illustration of the first point may be taken the census returns of France for the year 1831; in which there appears as the average of the whole kingdom,. 1 illegitimate for 13,2 legitimate births, while for Paris the average was 1 66 1,9 66 births. I am very far from saying or thinking that this difference is manifested in other countries, where the social precepts in this respect are more positive.

66

The proportion of still-born infants appears on an average, in Europe, to be 3 in illegitimate for 1 in legitimate birth; and this, I apprehend, would be found to hold here.

The mortality of mothers at accouchement, is an interesting point connected with what we have been considering; and it is much to be desired that there were more data upon it. I have already adverted to the great mortality of females during the age of fecundity, of which child-birth is an important element. Hitherto the information upon this, has been derived from the reports of lying-in hospitals; where so much depends upon the administration, as to leave a wide margin of variation. As far as can be judged from the hospitals of London, Edinburg, Dublin and Paris, under their later regime, the average mortality of mothers at such occasions, may be stated, at a mean, as 1 in 100; and the comparative mortality of mother and child under the same circumstances, may be taken as 1 to 3. But these proportions will hardly be expected to apply to the mass of cases which occur amid the greater comforts (mental, if not bodily) of domestic appliance and the always greater attention of friends at home.

I return now from this digression to the establishment of the factor for relative mortality at different ages. The last column of the table just given, shews the mean proportion of the dying to the dead; the next step is to determine their proportion to the living. The product of the mean proportion at each age with the average annual mortality, gives the average annual number of deaths corresponding; and the continual subtraction of these numbers from the aggregate and successive remainders, leaves a column of survivors, from which it is easy to distribute a population (supposed stationary) according to the periods of survival. The proportion, then, of the successive differences of the numbers thus distributed to the numbers themselves, is the relative mortality required. It is upon this method that I have constructed the following Table.

Aggregates, 2586

This table shews very distinctly what was intended by the influence of Age on mortality, and the greater or less probability of death according to the different periods. The numbers in the last column are, in fact, the ordinates for the curve of life, of which I spoke before; and may be employed for the graphic construction of such a curve.

The numbers employed are the aggregates of twenty years; but in order to shew the comparative relations of mortality here at different intervals, and to render them more readily comparable too with statements that have been made for other places, I offer the following

Table of Survivorship and Probable Life for successive periods.

The numbers in the columns of probable life are not extended beyond 80 years; because at that age they tend to become stationary. It is usual, in tables of mortality hitherto, to adjust the rates at the close of life so as to avoid their apparent irregularity and caprice, and to shew an uniformly decreasing progression. I have not thought it proper to resort to any artifice of this sort. Besides, the columns of

survivors show in fact the distribution. Thus, from the experience of the first period, if the laws which governed then were permanent, out of 100000 persons born at the same instant, there would be 9 who should have survived to the age of 120; in the second period, there were only 5 chances out of 100000 for the attainment of such an age; in the last, all would die before that age. It appears, then, that the absolute longevity has diminished here, in twenty years; though the chances of life for middle and mature age have improved. For infants, and especially at birth, they have materially diminished; and in this respect approach more nearly what has been observed in the larger European Thus the probable life at the moment after birth is in

cities.

This probable life must not be confounded with what the English writers generally term the expectation of life. It is in point of fact only the number of years elapsing from a given age until the living at said age shall have been reduced to one-half. It is obvious that during such a lapse, the chances of any individual of the given age for surviving are more than even, i. e. his life is probable; when the numbers of living and dead from the given age are equal, the chances are even; after that, they become in this aspect unfavorable. But the expectation of life, or more properly the mean life of any individual, is the number of years given by the proportion of all the chances to the favorable ones. If out of any community, the same number of persons died every year, then the mean life and the probable life would be equal. I have not calculated the mean life for the preceding table; because in order to give it directly, the intervals and corresponding numbers should be annual. It is not accurate to calculate it from 10 to 10 years, unless under the assumption that the mortality of the interval is regular, which is not in fact the case. I have made such assumption, it is true, even for the probable life; but here the inaccuracy is less in theory, and besides, for purposes of comparison like the present, it is immaterial. The data which I have presented are, to be sure, sufficient for the construction of a table in which the number of annual survivors should be given; which is, in fact, the form of the ordinary life-tables. But as the calculations for it are mere toil, without novelty in the methods, and with foreseen results, they have no interest for me. I have only resorted to them for the purpose of establishing the term of 20 years as in the preceding table, instead of 21 years for which the numbers are

given by direct observations. As there is no particular importance to be attached to this last term, and certainly none in its relation to mortality, it would contribute to symmetry and a more ready application, if the former were substituted in future in our Health-returns.

In making this interpolation, I have used the elements of the common parabola, a curve to which that of life plainly conforms. If any one should be tempted to construct a Table of Mortality for each year, circular elements might be employed for the whole reach from 10 years upwards; or without material error, the numbers may be interpolated by the method of which I have already spoken, taking them three by three from 100 years downwards. At that remote period, it would not be surprising if the anomaly already indicating itself in the tables should be manifested by a decrease of survivors for some of the younger lives. This, although it has been sedulously avoided or corrected by previous computists, I am inclined to regard as an evidence of periodical variations through the whole extent of human life.

In connection with this question of periodicity, it is much to be desired that some of our surgeon-accoucheurs whose experience must furnish them with the means, would give the results of observations on the human fœtus at different periods of gestation, principally in respect to its developement and its liability at one time more than another to fatal accidents. It is generally assumed, for instance, that the fifth and seventh months after conception, are more critical than the sixth and eighth. If these or some other terms should be so established (of which there is very little reason to doubt) upon a sufficient number of reliable observations, there would then be data for analogy between human life before and after birth; and the parallelism or concurrence of both would lead to an important generalization, for we could then continue the curve of life below the zero point and, so to speak, examine its negative equations. At present, I believe, we are wholly without elements for this end. I may be permitted to observe that it is not so much the medical relations which is desirable-not a discussion of proximate or final causes-as the simple establishment of the facts and terms. The aspect in which the laws of mortality are presented to the scientific inquirer, is less why men die, or how they die, than when they die; and the aim of the research, overlooking the fatalities or the casualties of single individuals, it is to discover and demonstrate in a comprehensive generality the laws or the accidents of the average Man-of man considered as the type of a class (and that the highest) of beings inhabiting the earth. For this, we observe him during his period of voluntary activity while living; we study him after his death: the complement of the research is to study him also before his birth.

In this general aspect, then, a topic that has been already adverted to in the beginning of this article and is included in our Health-returns, viz. the prevalence of particular diseases, either uniformly or occasionally-becomes of less importance. Nevertheless as sickness and suffering are the aids and precursors of mortality, and as divers diseases affecting a locality may be regarded as artificial (i. e. removable by effort and skill) this point too must properly find a place in any discus