2. PROBABILITY OF LIFE; or _the probable duration of life_, _la vie probable_. These are synonymous terms, in use chiefly among continental writers as an expression of the comparative duration of life. The tabular methods of setting forth the duration of life consist, for the most part, in assuming that 10,000 infants are born; and that at the age of one, two, three, and each successive year of life, there are so many still remaining in existence. Fix on any age; observe what number remain alive to commence that age; note at what age this number decreases to one-half; the age at which they so come to one-half is called the probable term of life; because, say the continental writers, it is an equal wager whether a person shall or shall not be alive at that period. Thus, suppose one thousand males commence together the age of eighty-four; suppose the table indicate that there will be alive at the age of eighty-five, 817; at the age of eighty-six, 648; at the age of eighty-seven, 493; at the age of eighty-eight, 357, and so on. In the present case, the probable duration of life at eighty-four is said to be very nearly three years, because, at the age of eighty-seven there are left alive 493, very nearly one-half of the thousand that originally started together. 3. VALUE OF LIFE. This term, when used accurately, expresses the duration of life as measured by one or other of the methods already expounded. But it is sometimes popularly used in a loose and singularly inaccurate sense. Thus it is very commonly said—"Such a man's life is not worth ten years' purchase," which is the same thing as to say, that an annuity, suppose a hundred pounds a year, payable during the life of the person in question, is not worth ten times its magnitude, that is one thousand pounds. If a thousand pounds be put into a bank at some rate of interest to be agreed upon, and if a hundred pounds be drawn every year from the stock, the expression under consideration affirms that the person in question will be dead before the principal and interest are exhausted. For instance, at four per cent., the value of an annuity of one hundred pounds to a man of the age of twenty-five is 1694_l._, which is 16-9/10 years' purchase; whereas, his expectation of life at that age is 35-9/10 years.