312 NATURAL THEOLOGY. 



served but to admire, the satisfaction, no less than 

 the regularity, with which the greatest part of the 

 irrational world yield to this soft necessity, this 

 grateful vicissitude ; how comfortably the birds of 

 the air, for example, address themselves to the 

 repose of the evening, with what alertness they 

 resume the activity of the day. 



Kor does it disturb our argument to confess 

 that certain species of animals are in motion dur- 

 ing the night, and at rest in the day. With res- 

 pect even to them, it is still true that there is a 

 change of condition in the animal, and an external 

 change corresponding with it. There is still the 

 relation, though inverted. The fact is, that the 

 repose of other animals sets these at liberty, and 

 invites them to their food or their sport. 



If the relation of sleep to nighty and, in some 

 instances, its converse, be real, we cannot reflect 

 without amazement upon the extent to which it 

 carries us. Day and night are things close to us ; 

 the change applies immediately to our sensations; 

 of all the phenomena of nature, it is the most ob- 

 vious and the most familiar to our experience ; 

 but, in its cause, it belongs to the great motions 

 wiiich are passing in the heavens. Whilst the 

 earth glides round her axle, she ministers to the 

 alternate necessities of the animals dwelling upon 

 her surface, at the same time that she obeys the 

 influence of those attractions which regulate the 

 order of many thousand w^orlds. The relation, 

 therefore, of sleep to night is the relation of the 



