16 THE FUR SEALS OF THE PRIBILOF ISLANDS. 
therefore be taken, and in a mile of rookery space the number of distinguishable 
marks of this sort is exceedingly small. Where stones exist, there are thousands of 
them practically indistinguishable. On bare slopes, as on Gorbatch, Vostochni, and 
Polovina, there are no natural landmarks whatever. 
THE ABSENCE OF RELIABLE SURVEYS. 
If perfectly recognizable artificial landmarks could be placed at every angle, turn, 
and projection of the belt of breeding seals, or if these points could be taken from a 
distance by instruments and then reproduced with certainty in the same manner after 
the animals have left the ground, accurate results might be obtained. Nothing of 
this kind, however, was done, at least no landmarks remain to show for it. 
THE IRREGULAR NATURE OF THE GROUND. 
But a determination of the rookery borders is not the only difficulty. The 
character of the ground is extremely variable. It lies at every conceivable angle 
and slant. ‘There are narrow, rocky beaches hemmed in by perpendicular cliffs. 
There are long slopes of jagged bowlders. There are sand flats and cinder slopes. 
On the bare places the seals still mass together as closely as they can be crowded, 
and on the rocky areas they lie about among the rocks as best they can. Their 
distribution over the rookeries is as irregular as the nature of the ground. 
It is in general true that the greater the number of females the more extended are 
the boundaries of the rookeries; but it is also true that with the decrease of the 
number of seals the population of the rookeries grows sparse without a corresponding 
decrease of dimensions. It is probable that when the seals were more numerous 
they were as evenly distributed over the ground as its nature would permit, and 
the greater part of each rookery was closely massed; but at the present time their 
distribution is very irregular, as unequal as the arrangement of the trees in the 
forest. On some of the rookeries, as on Tolstoi sands, in the breeding season the 
seals lie as thick as swarms of bees. On other rookeries, as the Lagoon, detached 
harems sprawl over the rocks and individual seals are greatly scattered. Nor are 
the mechanical imperfection of these estimates all. The counts of live pups made 
during the seasons of 1896 and 1897 show that at the time when these past estimates 
were made not more than half of the cows are present at any one time. 
ACREAGE MEASUREMENTS CHIEFLY GUESSWORK. 
In a word, the acreage measurements of the rookeries in the past have been based 
chiefly upon guesswork. More guessing has been done in determining the space to 
be assigned to individual animals, and finally the rookery population sought to be 
enumerated has at best represented only about half the actual number of animals 
belonging to the herd. The last element of uncertainty was not known until 1896, it 
having been assumed up to that time that during the period between the 10th and 
20th of July all or practically all the animals belonging to the breeding herd were 
present upon the rookeries. 
THE MAGNITUDE OF THE PROBLEM. 
It is easy to find in the magnitude of the problem an explanation for the adoption 
of such a faulty method. It is not so easy to find an excuse for implicit reliance 
