40 PHYSICAL SCIENCE BK. i 



instate daylight, until their fuel is used up, and they 

 gradually grow dimmer, and by and by, just like a 

 flame which is dying out, are by gradual subsidence 



3 reduced to nothingness. Some of these appear in 

 the clouds, some above them : in such cases the 

 thick air nearer the earth feeds them for a long time, 

 but eventually forces them right up to the stars. 

 Certain of these last no considerable time : they 

 straightway dart across the sky, or are extinguished 

 just at their point of origin. These are called 

 gleams because their appearance is fitful and short- 

 lived, though their fall is not always unattended by 

 injury : they have often caused as much damage as 

 lightning. One has seen houses struck by them, 

 what the Greeks call astrapoplecta * ( = star-struck). 



4 Those that have a longer career and a stronger fire 

 which follows the motion of the heavens, or those 

 that pursue an orbit of their own, are regarded by 

 the Stoic philosophers as Comets : of which more 

 anon. Different kinds of these zxepogoniae (bearded), 

 lampades (torches), and cyparissiae (like cypress 

 trees), and all the rest of them : they have a thin 

 tail of fire. It is doubtful whether beams (trades) 

 and the rare barrel -meteors (pithitae) should be 



5 placed in this category or not. Such meteors re- 

 quire a great mass of fire, since their immense orb 

 sometimes surpasses in size that of the morning sun. 



Among these should certainly be placed a pheno- 

 menon of which we often read in the chronicles 

 the heavens appeared to be on fire. The blaze 

 of it is occasionally so high as to mount to the very 

 stars ; occasionally it is so low as to present the 



6 appearance of a distant fire. In the reign of 



1 The term might also mean struck by lightning. A commoner reading 

 gives the meaning : which, when grazed by this means, the Greeks called 

 plecta ( = struck). 



