1. Recent investigation has brought to light the fact that the usual formulae are not necessarily practicable for the calculation of the force of mortality at very young ages. The problem is not only of considerable theoretical interest, but is also of practical importance to the Industrial Assurance Companies, which transact a very considerable volume of business at these ages. These companies use continuous functions for their various calculations, and μ being large at these very young ages, variations in the method of calculation are of such importance as to justify a detailed examination of the matter.