COMETS. 40 T 



extended itself to the upper part of the heavens, 

 flaming.* Exaggerated as these descriptions 

 may seem, they were almost equalled by the 

 appearances of the great Comet of the year 1680. 

 With all the phenomena which belong to 

 Comets, it appears that they are bodies con- 

 sisting of materials in a state of violent com- 

 bustion, and that they are not what Sir I. 

 NEWTON supposed them to be, " solid, com- 

 pact, and fixed, and durable bodies, Mke the 

 bodies of the planets ;" for he goes oa to say, 

 " If they were nothing else but vapors^ or the 

 exhalations of the earth of the sun, and the 

 other planets : this Comet, in its passage by 

 the neighbourhood of the sun, would have been 

 immediately dissipated;" for Sir Isaac assumed, 

 that the heat of the sun, is as the density of its 

 rays, that is reciprocally as the square of the 

 distances of the place from the sun. Therefore, 

 since on Dec. 8, when the Comet was in its pe- 

 rihelion, the distance thereof from the centre 

 of the sun, was to the distance of the earth 

 from the same, as about 6 to 1000, the sun's heat 

 on the Comet, was at that time, to the heat of 

 the summer's sun with us, as 1,000,000 to 36; 

 or as 2.8,000 to 1. But the heat of boiling wa- 

 ter is about three times greater than the heat 

 which (Jry earth acquires from the summer 



* His. Byz. Due Mich Nepot. 

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