486 THE POPULAR SCIENCE MONTHLY, 



One of the greatest among these was Jan de Witt, Grand Pen- 

 sionary of Holland and West Friesland, a disciple of Descartes, and 

 author of a mathematical work of note. 



About contemporary with him, the eminent French thinker, Pas- 

 cal, had laid down the first principles of the doctrine of chances. The 

 celebrated Christian Huygens enlarged upon these inquiries in a trea- 

 tise written in Dutch. When, in 1671, the States-General applied to 

 De Witt to elaborate the best plan for raising a loan, he was the first 

 to apply the principles of the science to a practical subject. In a mem- 

 orable report he states that, for reasons given, it is better to negotiate 

 funds by life-annuities, which by their nature are terminable, than to 

 resort to either perpetual or terminable annuities. He shows that it 

 had long been the practice in Holland to grant life-annuities at double 

 the rate of interest current. That is to say, if four per cent, was cus- 

 tomary, a loan of one hundred florins would bring four florins per 

 annum, while one hundred florins applied to the purchase of a life- 

 annuity would yield an income of eight florins. He goes on to 

 prove that the practice of making no distinction between the ages, 

 the selling a life-annuity on the same terms to the young and the 

 old, was based on a fallacy. He then applies the doctrine of chances 

 to data, most likely deduced from former annuity experiences, and 

 proceeds to construct a mortality-table. This table, though erroneous 

 in many respects, is still the first application of mathematical prin- 

 ciples to questions of this kind, and, as such, deserves the highest 

 consideration. 



The report was never acted upon, and was lost before De Witt's 

 contemporaries had become acquainted with it. 



Toward the end of the seventeenth century, the subject of calcu- 

 lating a table of mortality began to create interest in scientific circles 

 in England ; but the difficulty was, to obtain reliable statistics. A 

 few registers had been kept since 1538, and by 1600 they had been 

 introduced into probably one half the parishes of England. Unfor- 

 tunately, only births or baptisms had been entered. During the 

 plague, the government was induced to publish mortality bills, show- 

 ing the number of deaths ; but here, also, the ages were not stated. 

 The Royal Society, finding no data at home, turned to the Continent 

 of Europe. 



The city of Breslau, in Silesia, had kept an exact register of births 

 and deaths for some time, and reliable copies for the five years from 

 1687 to 1691 were obtained. These were intrusted to the Astronomer 

 Royal, the celebrated Dr. Halley, renowned for having calculated the 

 orbit of a comet, which has been named after him. He published a 

 treatise, which appeared in the "Philosophical Transactions" in 1693, 

 giving the following mortality-table, the first that had ever been con- 

 structed on exact scientific principles : 



