ESTIMATING THE NUMBER OF SEALS. 135 



rocks, sometimes entirely out of sight and most tiroes beyond computation. I found 

 that every factor of the calculation would have to be estimated averages, and that 

 these averages in their turn had to be founded upon estimated items; in short, that 

 the whole calculation would have to be a product of guesses multiplied by guesses. 

 As we have to deal with large figures, it is evident that a mistake in the estimated 

 factors must result in disastrously great mistakes in the total number. 



Suppose, for instance, that I had "estimated" the area covered by the seals on 

 both islands to be 4,000,000 square feet. If I " estimated " the average ground covered 

 by a seal (mother, pup, and bachelor) on the rookeries to be 2 square feet, I would obtain 

 a total of 2,000,000 seals on the Commander Islands. But, on the other hand, if I 

 guessed that on the average a seal, large and small, on the rookery occupies 5 square 

 feet — and this would possibly have been more nearly correct — I would get only a 

 total of 800,000 seals, large and small. According to this method, various persons 

 might estimate the number of seals on north rookery, Bering Island, from 20,000 

 to 120,000, and yet it might be impossible to convince any of them that they were 

 mistaken. 



A numeration of the seals being utterly valueless unless accurate, or at least 

 approximately accurate, I naturally regarded such an estimate of the number of seals 

 on the rookeries not only as useless, but as downright pernicious. Actual counting 

 being impracticable, and an individual judgment of the number being about as 

 valueless as the above method of calculation, unless acquired by a very long practice, 

 I gave up all attempts at presenting figures. 



When, after twelve years, I again visited these rookeries the same question 

 conironted me. In one place, where I had an unusually good opportunity, I tried to 

 make an estimate of the average area occupied by a seal on that particular rookery. 

 On July 16, watching the seals before me on Kishotchnoye rookery, Bering Island, I 

 wrote in my notebook as follows : 



Here is a harem right in front of me, 1 sikatoh, 16 matki, and ahout as many pups. They are 

 lying as close together as about the average, and they easily cover a, piece of ground 20 by 20 feet, 

 400 sq^uare feet, or more than 11 square feet per animal, pups and all. Ten square feet per animal for 

 this rookery is, therefore, I think, a fair estimate: 



But when I came back to the north rookery and tried to apply my estimate, I was 

 entirely at sea. I could not make up my mind whether the seals on the average were 

 lying as close as above, or closer. Of course, I could see places where they were 

 thicker, and others where they were thinner, but I could not, to my own satisfaction, 

 strike an average, if for no other reason, because there were great portions of the 

 rookery of which I could get no general view. Under those circumstances I would 

 have regarded it as the merest humbug to present any figures pretending that they 

 meant anything. Consequently, I wasted no further time upon getting at the iirobable 

 number of seals on the Commander Islands rookeries. 



The only method which promises reliable results is the one adopted now on the 

 Pribilof Islands by the experts of the United States Fish Commission, viz, to actually 

 count the number of seals on several large tracts of rookery, each of the size of an 

 acre or more. In this way an average per acre may be obtained, which, multiplied 

 by the computed acreage of all the rookeries, will give an approximate number which 

 may not be too far out of the way. But, unfortunately, this method is hardly appli- 

 cable to the Commander Islands, for various reasons, chief of which is the impossibility 



