784 
As this annual increment is at the best 
small and as for ten years there has been a 
steady loss, it seems apparent enough that 
the number that might be taken with safety 
has been very much exceeded. 
It is conceded that pelagic sealing has of 
late fallen off in a greater ratio than the 
herd, thus producing a tendency toward 
equilibrium innumbers. Thissimply means 
that over 60,000 seals were taken in 1895 ; 
43,000 in 1896, and 26,000 in 1897, so that 
the pelagic catch has fallen off one-half in 
three years, although the herd has not di- 
minished by one-half in the same time. 
It is to be feared that before any equi- 
librium could be reached but a small por- 
tion of even the present number would be 
left, and this leads naturally to the next 
point agreed upon, which is that in estima- 
ting the future conditions of the herd the 
reduction in the number of pups caused by 
the pelagic catches of 1894 and 1895 must 
be taken into consideration. 
For example, not less than 20,000 pups, 
half of them females, perished of starvation 
in 1895, owing to the death of their mothers 
Not only did the 
portion of this number that would have 
from pelagic sealing. 
survived fail to appear on the rookeries in 
1897, but the number of births will be nat- 
urally lessened by just that number in 1898 
and the progeny of these in turn fail to ap- 
pear in 1900. Thus, as the natural decrease 
will go on, while the natural increase has 
been cut off, effects of pelagic sealing will be 
felt up to 1900, even should it be stopped 
at once. 
The final conclusion is that the herd is 
not in danger of actual extermination so 
SCIENCE. 
[N. S. Vou. VI. No. 152. 
long as its haunts on land are protected 
and the protected zone about the islands is 
maintained, and that both land and sea 
killing now yield an inconsiderable profit. 
The seal herd is in fact very far from actual 
extermination, although the point of com- 
mercial extermination, or that where the re- 
turns are wholly incommensurate with the 
amount of capital invested, has been nearly 
reached. But for the prompt action of the 
United States in 1869 this point would 
have been reached years ago, while but for 
its care of the islands ever since practical 
extermination would not be far off. 
The example of the Southern fur-seal 
illustrates the rapidity with which commer- 
cial extermination may be effected, while 
the fate of the fur seals on the Farallones, 
Guadalupe and Juan Fernandez shows how 
readily actual extermination may take 
place. The Pribilof Islands are not, like 
those of the Antarctic, difficult of access, and 
their abandonment by this government 
would lead to the actual extirpation of the 
On the 
other hand, with proper protection the fur- 
fur seals within a very few years. 
seal herd can, with but little care and cost, 
be made an important source of revenue so 
long as fashion may decree the wearing of 
of seal-skin sacques. 
THE PSYCHOLOGY OF THE PERSONAL EQUA- 
TION. 
In the present paper the writer proposes 
to maintain the thesis that the personal 
equations of astronomers are mainly con- 
trolled by known laws of experimental psy- 
chology and hopes to assist his professional 
brethren in making use of the researches of 
the psychologists in such a manner that 
they shall avoid groundless hypotheses 
