AN ESSA V ON LONGEVITY. 1 1 



tistics, individual assertions, general impressions, ex- 

 periment. It might be supposed that statistics would 

 furnish very valuable evidence on this matter ; but, 

 in the first place, it is only within certain European 

 areas and a part of America that statistics relating 

 to age are prepared, and the qualifications to which 

 these are subject, from the shifting of population, are 

 of a very complex character ; further, there is a re- 

 markable personal equation in the observers, who 

 are at the same time the subjects of the enquiry 

 into age, which it seems almost impossible fairly 

 to estimate. Men do not tell the truth as to their 

 age, either from ignorance or from deceitfulness. The 

 ill-educated and the aged are specially likely to make 

 false statements from ignorance, whilst that 'vanity 

 which never grows old ' ^ affects equally the state- 

 ments of old and young. 



Individual assertions, taken alone and apart from 

 the correction which the average of a vast number 

 must ensure, are of course still less to be depended 

 upon, and for the same reasons. General impressions, 

 such as are imparted to us by travellers, by poets, and 

 even historians, are of very small value when they 

 relate to the duration of life, where it is so easy to 

 confuse wear and one of its factors age. Experiment 

 of what will ensure long duration of life in himself 

 has been too rarely tried by man to make this class 

 of evidence of any scientific value, whilst amongst 

 1 Buffon. 



