In a paper published some time back in the Journal of the Institute, an endeavour was made to show the true principles upon which the value of securities depending on an isolated human life should be determined. Discarding the methods once so generally practised, and in accordance with which such securities were confounded with those depending on the average duration of many lives, it was urged that they should be regarded in a distinct point of view, and as affording the means of investments to be made not subject to any contingency whatever, but as securing to the holder a given rate of interest so long as he retains them, and the return of the capital invested when such interest shall cease to be paid or to accrue.

I. The object of the first part of this memoir was to determine the normal course of mortality as affected by age alone, without reference to other circumstances.

What we name the law of mortality is not a simple law, but a compendious expression, by which we denote the operation of various laws, physiological, physical, and moral. Of these, the physiological laws are so uniform in their operation that they impress certain characteristic features upon the law of mortality, according to age, which are observed amidst all the diversities which it exhibits under varying circumstances, physical and moral.