252 CLASS AVES. 



causes. The owl is not made for the full light of day, and can 

 live only, for all the active purposes of life, in partial darkness ; 

 the dusk of evening, or gray of the morning, is essential to the 

 full exercise of her vision ; the noonday sun, or even the pre- 

 sence of that luminary any where above the horizon, dazzles 

 and blinds her by the influx of too much light consequent 

 on the uimsual largeness of the disk of the eye-pupil : but 

 this very circumstance, which is a source of so much inconve- 

 nience to the animal by day, is, in fact, an admirable con- 

 trivance for the perfection of vision during the comparative 

 darkness of twilight or night. When the rays of light are 

 diffused, and cannot find access in sufficient quantity to the 

 ordinary pupils of diurnal animals, the capaciousness of those 

 of the owl takes in enough for the perfect use of the eye : the 

 shape of the pupil seems to be unimportant, but the capacious- 

 ness of its disk is certainly essential to nocturnal vision. 



Although, however, the eyes of these birds will admit light 

 enough for all purposes of vision during twilight, they will not 

 enable them to see sufficiently during the darkness of night; 

 and consequently, as they cannot see from redundancy of light 

 during day, and from want of it during the greater part of 

 many nights, they have very short space of time left them for 

 procuring their food. 



It is observable, from the quality of animal and vegetable 

 food, that animals which feed on the former are capable of en- 

 during abstinence much longer than these which subsist on the 

 latter: if, therefore, this fact be considered in conjunction with 

 the conditions of these birds just alluded to, we may fairly con- 

 clude, that if owls had been vegetable eaters, they would soon 

 have all starved : for, without some special provision against 

 such a consequence, the short spaces of time they could appro- 

 priate to procuring food would be insufficient to enable them to 

 collect vegetable matter in sufficient quantity; but the owl, 

 which is necessarily abstinent, is carnivorous : — so congruous 

 are the works of nature. 



