SUCCESSORS OF NEWTON IN ASTRONOMY 



as upon its ascension or otherwise illumination, to 

 give a light to a circle of above one hundred miles 

 diameter, not much inferior to the light of the moon ; 

 so as one might see to take a pin from the ground in 

 the otherwise dark night. 'Tis hard to conceive what 

 sort of exhalations should rise from the earth, either 

 by the action of the sun or subterranean heat, so as to 

 surmount the extreme cold and rareness of the air in 

 those upper regions : but the fact is indisputable, and 

 therefore requires a solution." 



From this much of the paper it appears that there 

 was a general belief that this burning mass was 

 heated vapor thrown off from the earth in some 

 mysterious manner, yet this is unsatisfactory to Hal- 

 ley, for after citing various other meteors that 

 have appeared within his knowledge, he goes on to 

 say: 



"What sort of substance it must be, that could 

 be so impelled and ignited at the same time; there 

 being no Vulcano or other Spiraculum of subterra- 

 neous fire in the northeast parts of the world, that 

 we ever yet heard of, from whence it might be pro- 

 jected. 



" I have much considered this appearance, and think 

 it one of the hardest things to account for that I have 

 yet met with in the phenomena of meteors, and I am 

 induced to think that it must be some collection of 

 matter formed in the aether, as it were, by some 

 litous concourse of atoms, and that the earth met 

 with it as it passed along in its orb, then but newly 

 formed, and before it had conceived any great impetus 

 of descent towards the sun. For the direction of it 



9 



