472 Correspondence. [July, 
about to settle, when it made a semicircle before alighting. I 
thought this movement was exceptional, but, continuing my ob 
servations, I found that all the rooks made a half circle against 
the wind before settling. I thought it a curious instincfl. Re- 
peated observations have confirmed me in the idea that it is their 
universal habit, occasioned, I suppose, by the necessity of 
breaking the impetus of the momentum acquired by their down- 
ward flight on the wind. The change in direftion is probably 
occasioned by the interstices to be observed in the spreaded wing 
of a rook, disabling them by any other means to arrest the 
acquired velocity. The turn made is always against the wind, 
and even then on settling they appear to strike the ground with 
a heavy thud. Doubtless was the ground reached in direct 
downward flight, the weight of the bird and the inability of con- 
trol — occasioned, most likely, by the interstices between the 
feathers of the wings — would cause fracflure or other serious in- 
convenience. — I am, &c., 
S. B. 
ORIGIN OF THE PERCEPTION OF NUMBER. 
To the Editor of the Journal of Science . 
Sir, —A little boy, the son of a friend of mine living at Ayles- 
bury, seeing three rooks perched on the branch of a tree, 
exclaimed, “Quo, quo, quo!” It struck me that these words 
explain the manner in which the number of objedls is appre- 
hended by young children and by the lower animals.- — I am, &c. * 
C. S. 
