226 PHILOSOPHICAL TRANSACTIONS. [aNNO J 7 J 6. 



medium between the balls, so as to make a perpetual day below. That very 

 great tracts of the etherial space are occupied by such a shining mediutn, is 

 evident from the instances given in the first paper of this Transaction : and if 

 such a medium should be thus inclosed within us; why may we not be allowed 

 to suppose that some parts of this lucid substance may, on very rare and ex- 

 traordinary occasions, transude through and penetrate the cortex of our earth, 

 and being got loose may afford the matter of which this our meteor consists. 

 This seems favoured by one considerable circumstance, viz. that the earth, be- 

 cause of its diurnal rotation, being necessarily of the figure of a flat spheroid, 

 the thickness of the cortex, in the polar parts of the globe, is considerably 

 less, than towards the equator; and therefore more likely to give passage to 

 these vapours ; whence a reason may be given why these lights are always seen 

 in the north. But I desire to lay no more stress on this conceit than it 

 will bear. 



It having been noted that in the years 1575 and 1580, when this appearance 

 was frequent, that it was seen not far from the times of the two equinoxes; 

 it may be worth while for the curious to bestow some attention on the heavens 

 in the months of September and October next ; and in case it should again 

 happen, to endeavour to observe, by the method I have here laid down, what 

 may determine, with some degree of exactness, its distance and height ; with- 

 out which we can scarcely come to any just conclusion. 



A Description of the Phenomenon of March Q, 1716, as it was seen on the 

 Ocean^ near the Coast of Spain, With an Account of the Return of the 

 same Sort of Appearance, on March 31, and April 1 and 2, 1717' N° 348, 

 p. 430.* 



In our last, we endeavoured to give the public as good an account of the 

 late surprising meteor, seen in the heavens, on the 6th of March last, as could 

 be gathered from the several relations of very distant spectators. And since 

 then, we can only add, that at Paris, the light was so inconsiderable, that it 

 was not regarded: but by a letter, dated on board a ship in Nevis road, in 

 America, April IQ, 17l6, is the following psssage. " On the 6th of March, 

 at 9 o'clock in the evening, we being then in the lat. of 45° 36', off of the 

 N. W. coast of Spain, a clear cloud appeared east of us, not far distant from 

 our zenith, which afterwards darted itself forth into a number of rays of light, 

 every way like the tail of a comet, of such a great length, that it reached 



* Probably by Dr. Halley. 



