194 The November Shooting Stars. 



meteor is vertical. We have very strong evidence, showing 

 that 70 miles is about the height at which meteors appear, the 

 evidence of meteors appearing at a greater height being very 

 doubtful. Hence, when a meteor is seen low down towards 

 the horizon, it may be confidently assumed that the point over 

 which this meteor is vertical lies within 750 miles of the place 

 of observation. Now the ovals and circle in Maps 1 and 2 

 mark the limits of the space over some point of which a 

 meteor must be vertical to be seen from the centre of the space. 

 For instance, a meteor appearing at a point vertical over 

 Madrid, or Turin, or Berlin, or Stockholm, might just be 

 visible from London, appearing just above the horizon ; but a 

 meteor vertical over Gibraltar, or Rome, or St. Petersburg, 

 would not be visible in England. 



Now, if we consider Map 1, we shall see that about two 

 hours before the time indicated by that map (a quarter past 

 twelve at night), London is just becoming visible on the 

 edge of the earth's disk ; but the edge of the oval space round 

 London comes into view more than an hour earlier — that is, at 

 about nine o'clock. This is the earliest hour at which a 

 member of the November system can by any possibility be 

 seen in London. Meteors seen at this hour would be momen- 

 tarily visible in the eastern horizon, moving upwards. When 

 "London comes to the border of the visible hemisphere, 

 aieteors may be looked for over the whole space between the 

 ■©astern horizon (that is from south, through east to north) 

 &nd the zenith, travelling (more or less) upwards unless they 

 appeared nearly towards the north or south, when their motion 

 would be horizontal. When the whole of the London oval 

 space is in view, meteors may be looked for over the whole 

 heavens. A little consideration will show that at and after 

 this time, conspicuous meteors will be seen more plentifully 

 over the western half of the heavens. If the mere number of 

 meteors indeed, were alone considered, the contrary would be 

 the case. But the paths of meteors being from a point east of 

 London (it is clear that both in Map 1 and in Map 2, we are 

 looking at London from the east), they would have in general 

 an apparently westward motion, and all those having long 

 visible tracks would be towards the west. 



It is also evident from Figs. 1 and 2, that meteors increase 

 in number (eateris paribus) as England, through the earth's 

 rotation, approaches the centre of the disk visible from the 

 radiant point, or — which amounts to the same thing — as the 

 radiant point rises above the horizon. It is clear, for instance, 

 that the oval space round England in Fig. 2, is greater than the 

 oval in Fig. 1 j and that at an hour later than that indicated in 

 Fig. 2, the oval is yet greater. The oval round Englaud is 



