VOL. LXXIV.] PHILOSOPHICAL TRANSACTIONS. 523 



§ 4. Nothing relative to these meteors strikes the beholders with so much 

 astonishment as the excessive light they afford, sufficient to render very minute 

 objects visible on the ground in the darkest night, and larger ones to the distance 

 of many miles from the eye. The illumination is often so great as totally to 

 obliterate the stars, to make the moon look dull, and even to affect the spectators 

 like the sun itself; nay, there are many instances in which such meteors have 

 made a splendid appearance in full sun -shine. The colour of their light is various 

 and changeable, but generally of a bluish cast, which makes it appear remarkably 

 white. A curious effect of this was observed at Brussels the 1 8th of August, 

 that while the meteor was passing, " the moon appeared quite red, but soon re- 

 covered its natural light.'' The brightness alone of the meteor is not sufficient to 

 explain this, for the moon does not appear red when seen by day ; but it must 

 have depended on the contrast of colour, and shows how large a proportion of 

 blue rays enters into the composition of that light, which could make even the 

 silver moon appear to have excess of red. Prismatic colours were also observed 

 in the body, tail, and sparks of this meteor, variously by different persons ; some 

 compared them to the hues of gems. The moment of its greatest brightness 

 seems to have been when it burst the first time ; but it continued long to be 

 more luminous after that period, than it was before. 



The body of the fire-ball, even before it burst, did not appear of a uniform 

 substance or brightness, but consisted of lucid and dull parts, which were per- 

 petually changing their respective positions ; so that the whole effect was to some 

 eyes like an internal agitation or boiling of the matter, and to others like 

 moving chasms or apertures. Similar expressions have been used in the descrip- 

 tion of former meteors. The luminous substance was compared to burning 

 brimstone or spirits, Chinese fire, the stars of a rocket, a pellucid ball or bubble 

 of fire, liquid pearl, lightning and electrical fire ; few persons fancied it to be 

 solid, especially when it came near the zenith. Different spectators observed the 

 light of the meteor to suffer at times a sudden diminution and revival, which pro- 

 duced an appearance as of successive inflammation ; but might, in some cases at 

 least, be owing to the interposition of small clouds in its path. 



^ 5. When, in consequence of a more accurate attention to natural philoso- 

 phy, such observations were first made on fire-balls as determined their height, 

 the computers were with reason surprized to find them moving in a region so far 

 above that of the clouds and other familiar meteors of our atmosphere ; especially 

 as to every uninformed spectator they appear extremely near, or as if bursting 

 over his head, a natural effect of their great light when seen without intervening 

 objects. Their real height is to be collected from observations made at distant 

 stations, which, for the greatest accuracy, ought to be so situated, that the line 



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