REPORT OF AMERICAN COMMISSIONERS. 353 



tlie distribution of ages from tliis time on pre- ExpiniKitiou of 



diagrams. 



tends only to be an approximation, as it is impos- 

 sible to obtain the accurate information necessary 

 for a better representation. We maintain, how- 

 ever, tliat the fullest knowledge would necessitate 

 no change which would materially affect the 

 force of our argument based on these diagrams. 



The longest vertical line at the left represents 

 tlie number of births annually, which, for con- 

 venience, is assumed to be ten thousand of each 

 sex. At the end of one year the vertical line is 

 reduced one-half in length, as half the seals born 

 the year before are assumed to be dead. At the 

 end of the second year it is still further short- 

 ened, and so on until the end of the twentieth 

 year. There can thus be traced the history of a 

 group of ten thousand seals from birth to final 

 extinction, the area bounded by lines vertical at 

 the beginning and end of any year showing the 

 number alive at any age, as between ten and 

 eleven years of age, and tlie total area of the 

 diagram is proportional to the total number of 

 seals in the herd. 



Diagrams A and B represent the males and 

 females of such a herd in its natural condition, 

 that is, not interfered with by man. It is in a 

 condition of practical stability, the males and 

 females are equal in number, and the diagrams 

 pre identical, except as to the coloring of the 

 3716 45 



