VISION. 227 
We have not a doubt it is by the eye alone that 
the carrier pigeon (Columba tabellaria, Ray) per- 
forms those extraordinary aerial journeys which 
have from the earliest ages excited astonishment. 
We have frequently witnessed the experiment made 
with other pigeons, of taking them to a distance from 
the dovecot, expressly to observe their manner of 
finding their way back, and we feel satisfied that 
their proceedings are uniformly the same. On be- 
ing let go from the bag in which they have been 
carried, in order to conceal from their notice the ob- 
jects on the road, they dart off on an irregular 
excursion, as if it were more to ascertain the 
reality of their freedom than to make an effort to 
return. When they find themselves at full liberty, 
they direct their flight in circles round the spot 
whence they have been liberated, not only increas- 
ing the diameter of the circle at every round, but 
rising at the same time gradually higher. ‘This is 
continued as long as the eye can discern the birds, 
and hence we conclude that it is also continued 
after we lose sight of them, a constantly increasing 
circle being made till they ascertain some known 
object enabling them to shape a direct course. 
It is not a little interesting to contrast the pro- 
ceedings just described with those of a pigeon let 
off from a balloon elevated above the clouds. In- 
stead of rising in circles like the former, the balloon 
pigeon drops perpendicularly down like a plummet, 
till it is able to recognise some indications of the 
earth below, when it begins to wheel round in a de- 
scending spiral, increasing in diameter for the evi- 
dent purpose of surveying its locality, and discover- 
ing some object previously known by which to direct 
its flight. 
The rapidity with which the carrier pigeon per- 
forms long journeys may, perhaps, be adduced as 
an objection to this explanation. M. Antoine, for 
example, tells us that a gentleman of Cologne, hav 
