184 



HALLEY'S COMET. 



course, wholly omitted. Neither did Clairaut take into account the action of 

 the earth. Encumbered with the disadvantages of precision in his data, he 

 predicted, in his first memoir, that the comet would arrive at its nearest point 

 to the sun on the 18th of April, 1759 ; but he stated at the same tirre that the 

 imperfection of some of the methods of calculation he was compelled to adopt, 

 was such as to leave a possibility of his prediction being erroneous to the ex- 

 tent of a month. After presenting this memoir he resumed his calculations, 

 and completed some which he had not time to execute previously. He then 

 announced that the 4th of April would be the day of the comet's arrival at the 

 nearest distance to the sun. 



This wonderful astronomical prediction was accompanied by a circumstance 

 still more remarkable and interesting than that which we have noticed in the 

 conjectures of Halley as to the disturbing effects of the planets upon the com- 

 et's period. Clairaut stated that there might- be very many circumstances 

 which, independently of any error either in the methods or process of calcula- 

 tion, might cause the event to deviate more ordess from its predicted occur- 

 rence ; one of which was the probability of an undiscovered planet of our ays- 

 tern revolving beyond the orbit of Saturn, and acting by its gravitation upon the 

 comet. In twenty-two years after this time this conjecture was accurately 

 fuVilled by the discovery of the planet Herschel,by the late Sir William Her- 

 schel, revolving round the sun one thousand millions of miles beyond the orbit 

 of Saturn ! 



In the successive appearances of the comet subsequent to 1456, it was found 

 to have gradually decreased in magnitude and splendor. While in 1456 it 

 occupied two thirds of the firmament, and spread terror over Europe, in 1607 

 its appearance, when observed by Kepler and Longomontanus, was that of a 

 star of the first magnitude ; and so trifling was its tail, that Kepler himself, 

 when he first saw it, doubted if it had any. In 1682 it excited little attention 

 except among astronomers. Supposing this decrease of magnitude and bril- 

 liancy to be progressive, Lalande entertained serious apprehensions that on 

 its expected return it might escape the observation even of astronomers ; and 

 thus that this splendid example of the power of science, and unanswerable 

 proof of the principle of gravitation, would be lost to the world. It is not un- 

 interesting to observe the misgivings of this distinguished astronomer with re- 

 spect to the appearance of the body, mixed up with his unshaken faith in the 

 rce.ult of the astronomical inquiry. " We cannot doubt," says he, " that it will 

 return ; and even if astronomers cannot see it, they will not therefore be the 

 less convinced of its presence ; they know that the faintness of its light, its great 

 distance, and perhaps even bad weather, may keep it from our view ; but the 

 world will find it difficult to believe us ; they will place this discovery, which 

 has done so much honor to modern philosophy, among the number of chance 

 predictions. We shall see discussions spring up again in the colleges, con- 

 tempt among the ignorant, terror among the people, and seventy-six years will 

 roll away before there will be another opportunity of removing 'all doubt." 



Fortunately for science, the arrival of the expected visiter did not take place 

 under such untoward circumstances. As the commencement of the year 1759 

 approached, " Les Astronomes," says Voltaire, " ne se coucherent pas." 



The honor, however, of the first glimpse of the stranger was not reserved 

 for the possessors of scientific rank, nor the members of academies or univer- 

 sities. On the night of Christmas day, 1758, George Palitzch of Prolitz, near 

 Dresden, " a peasant," says Sir John Herschel, " by station, an astronomer by 

 nature," first saw the comet. He possessed an eight-foot telescope, with 

 which he made the discovery ; and the next day communicated the fact to Dr. 

 Hoffman, who immediately went to his cottage, and saw the comet on the even- 



