350 FALL OF COMETS TO THE SUN. SECT. XXXVI. 



zenith. As this comet is presumed to have a period of 

 575 years, the major axis of its orbit must be so great, 

 that at the aphelion the sun's diameter would only sub- 

 tend an angle of about fourteen seconds, which is not 

 so great by half as the diameter of Mars appears to us 

 when in opposition. The sun would consequently im- 

 part no heat, so that the comet would then be exposed 

 to the temperature of the ethereal regions, which is 58 

 below the zero point of Fahrenheit. A body of such 

 tenuity as the comet, moving with such velocity, must 

 have met with great resistance from the dense atmos- 

 phere of the sun, while passing so near his surface at 

 its perihelion. The centrifugal force must consequently 

 have been diminished, and the sun's attraction propor- 

 tionally augmented, so that it must have come nearer to 

 the sun in 1680 than in its preceding revolution, and 

 would subsequently describe a smaller orbit. As this 

 diminution of its orbit will be repeated at each revolu- 

 tion, the comet will infallibly end by falling on the sur- 

 face of the sun, unless its course be changed by the dis- 

 turbing influence of some large body in the unknown 

 expanse of creation. Our ignorance of the actual den- 

 sity of the sun's atmosphere, of the density of the 

 comet, and of the period of its revolution, renders it 

 impossible to form any idea of the number of centuries 

 which must elapse before this event takes place. 



The same cause may affect the motions of the planets, 

 and ultimately be the means of destroying the solar sys- 

 tem. But, as Sir John Herschel observes, they could 

 hardly all revolve in the same direction round the sun 

 for so many ages without impressing a corresponding 

 motion on the ethereal fluid, which may preserve them 

 from the accumulated effects of its resistance. Should 

 this material fluid revolve about the sun like a vortex, it 

 will accelerate the revolutions of such comets as have 

 direct motions, and retard those that have retrograde 

 motions. 



The comet which appeared unexpectedly in the be- 

 ginning of the year ]843, was on-e of the most splendid 

 that ever visited the solar system. It was in the con- 

 stellation of Antinous in the end of January, at a dis- 

 tance of 115 millions of miles from the earth, and it 



