The important and laborious investigation of which we give the results in the following pages is the last serious contribution to statistical knowledge by Mons. Marco Besso, a Fellow of the Institute of Actuaries of some years' standing, and an insurance expert of wide experience and great repute throughout the continent. The paper was at first published in part in the Bulletin de l'Institute de Statistique, and a translation subsequently appeared in the German Annual Magazine of Herr Ehrensweig.