*"X_-^*-* 



II ALLEY'S COMET. 



Predictions of Science. Structure of tho Solar System. Motion of Comets. How to identify them. 

 Intervals of their Appearance. Halley's Comet. Its History. Newton's Conjectures. S.- < t.-:icity 

 of Voltaire. Halley's Researches. Foretells the Reappearance of the Comet in 1759. Principle of 

 Gravitation applied to its Motion by Clairaut. Researches of that Mathematician. Anecdotes of 

 Lalunde and Madame Lepaute. Minute and circumstantial Krediction of the Reappearance of 

 Halley's Comet. Discovery of the Planet Herschel anticipated by Clairaut. Reappearance of 

 the Comet at the predicted Time. Second Prediction of its Return in 1830. Prediction fulfill- 

 ed. Observations on its Appearance in 1835. 



