Life Assurance provides for the family of the deceased in case of premature death; deferred Annuities provide for old age; but both institutions leave uncovered the risk of premature inability to work. Invalidity Assurance, including the benefits of a deferred Annuity, would be the real complement to Life Assurance. This truth is so deeply felt in Germany, that a good many institutions, employing a large number of officers, workmen, and labourers; many mills, and particularly the Railway Companies, long since directed their attention to the providing for their officers in case of their being invalided. How were they to calculate the annual contribution, how to make the valuation of their liabilities?