Meteorological Observations. 399 



ricrally appear in warm summer evenings, particularly when 

 cirrociiniulns and thunder clouds abound : some of them 

 are very beautiful, and give much light: they vary some- 

 what in colour and si^e. 



The third sort are strikingly different from the two above 

 mentioned : they are generally small, and of a beautiful 

 blueish-white colour; but their peculiar characteristic is that 

 of leaving long white trains behind them, which remain 

 visible for some seconds in the tract in which the meteors 

 , have gone. These tails seem to be lost by dispersion ; they 

 appear to fly off from all points, increasing in breadth as 

 they become fainter, till at last they cease to be distinguish- 

 able. They are generally seen in the intervals of showery 

 weather, and are most prevalent before the occurrence of 

 high wind ; of which they have been considered by Virgil 

 as a certain prognostic*. These luminous tails have so 

 much the appearance of the burning of some gas, that I 

 have been induced to propose it as a question, Whether hy- 

 drogen may not be so diffused in the atmosphere, that it 

 may be lighted by the meteor as it passes through itf? 

 From what I have been able to observe, these tails seem to 

 result rather from some such diffused gas set on fire by the 

 meteor in its passage, than from any of the luminous sub- 

 stance of the meteor left behind it. It may be also remarked, 

 that if the larger kind of meteors happen at the same time 

 that these caudate meteors are prevalent, they always leave 

 the tail behind then) J. 



I shall not, at present, speculate further on the causes of 

 igneous meteors in general, nor on the varieties in the state 

 of the atmos])here, by which their peculiarities may be ef- 

 fected, hoping that meteorologists will note them down ac- 

 curately in their journals. 



I remain, sir, your humble servant, 



Clapton, Nov. 15, 18U. ThoMAS FoRSTER. 



• GeaTf^c. lib. 1. 



t The separation of the gases of water has been noticed by M. B, P, 

 Van Mona. 



X The train of light wiiich the common meteors or falling stars appear to 

 leave behind, and which lasts scarcely a moment, is probably only a halluci- 

 nation of vision like the AcKixeaxicv tyx"! sung by Homer, and quoted by 

 Dr. Larwin, Zoon. sect. iii. 5. 3. — to which, as well as to his paper Z>e Ocu- 

 ioTum S^t Lilts, I refer the reader. 



METBORO- 



