514 lECTURE XLII. 



messengers forming a communication between the neighbouring systems of 

 the sidereal world, and visiting a variety of stars in succession, so as to have 

 their courses altered continually, by the attraction towards many different 

 centres; but considering the coincidenc« of the calculation of Hal ley and 

 Clairaut with the subsequent appearance of the comet of 1759, this 

 opinion can scarcely be admitted to be in any degree probable with respect 

 to the comets in general, however possible the supposition may be in some 

 particular cases. (Plate XXXII. Fig. 472 . . 475. Plate XXXIII. Fig. 

 476 . . 485.) 



