9 8 EX VI RIB US VIVIMUS. 



With these preliminary remarks on the nature of 

 the possible variations in human potential longevity, 

 we may proceed to some facts, and their interpreta- 

 tion, by means of the relations shewn to exist in 

 all organisms for longevity. 



15. Sources of Information as to Human Longevity. 



Before making enquiry, one is apt to suppose that 

 a good deal must be known as to the probable 

 duration of human life ; that there are, at any rate, 

 statistics of some nations or periods of which assur- 

 ance companies make use. But there are statistics 

 and statistics,^ and very few of the calculations re- 

 lating to this matter are of real value. Besides 

 statistics, as observed in a previous paragraph, we 

 have general impressions either brought home by 

 travellers or current amongst a people, and appearing 

 in their sayings, poetry, traditions, and philosophy. 



he believed himself that there is hereditary difference of life-tenure in 

 various races. But he gave no facts, and probably the explanation here 

 given of the apparent hereditary character may include all that he would 

 contend for. 



' Professor Huxley most truly observes that there are ' many cases in 

 which the admitted accuracy of mathematical processes is allowed to 

 throw a wholly inadmissible appearance of authority over the results 

 obtained by them. Mathematics may be compared to a mill of exquisite 

 workmanship, which grinds you stuff of any degree of fineness; but, 

 nevertheless, what you get out depends on what you' put in ; and as the 

 grandest mill in the world vrill not extract wheat-flour from peascods, so 

 pages of formulae will not get a definite result out of loose data.'— 

 Anniversary Address to the Geological Society, 1869. 



