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which the number of times it did not happen is the numerator.

Thus, if out of 100,000 persons, at age 10, 676 have died in one year, we consider that the chance that a person, aged 10, will die in one year is T0"' ~0'(, o; , and the chance that he will not die is T`'o0011u, while the chance that he will die, plus the chance that he will not tlie is

070= 00824 — 10.00.00_ = j or certainty.

' —lUVO64-.. — l0000U

In the application of this important principle lies the possibility of computing in advance, within reasonable limits of error, the cost of insurance. The value of the risk or probability- is estimated as closely as possible by means of averages drawn from past experience. The utmost care is, of course, necessary to ascertain that the conditions of the past experience, from which the awer-ages are derived; and of the future as to which insurance is to be given, are alike in all essential regards.

In life insurance alone are compound probabilities sometimes employed; as, for instance, in an insurance payable upon the failure of the first of two or more lives or an annuity, continuing during the life of the last survivor of two or more lives.

The chance of hawing to pay a death-claim because of the death within one year of the first of two lives is not quite the same as that of haying to pay a claim be-cause of the death of one, plus the chance of haying to pay a claim because of the death of the other; for in the latter case, if both were to die, two claims would be payable. So, in order to get the correct probability-, the chance of both dying within the year must be de-ducted from the chance of the first dying, plus the chance of the second dying.