The November Shooting Stars. 197 



however, utterly improbable, it may easily be calculated that 

 for every meteor grazing our atmosphere (at a height not 

 exceeding 70 miles), twenty-eight travel directly towards 

 the earth's surface. But the proportion must in reality be very 

 much greater, since our supposition implies the possibility of a 

 meteor travelling through the air in a direction actually tangent 

 to the earth's surface, or passing through about 1,450 miles ot 

 air, including the densest strata. Since meteors seldom pene- 

 trate to a vertical depth of more than twenty or thirty miles, 

 without dissolution, it is very unlikely that meteors travelling 

 parallel to the horizon should penetrate to a vertical depth 

 even of ten or fifteen miles — since, to do so, their actual path 

 through the air would be many times longer. Assuming that 

 meteors could escape after penetrating in this manner to a 

 depth of twenty miles, we should have, for every meteor so 

 escaping, almost exactly one hundred whose substance, whole 

 or dissolved, would reach the earth. Even escaping meteors 

 would never again appear as members of the November 

 shower, since their orbit, after grazing contact of the kind 

 supposed, would be very different (owing chiefly to their loss of 

 velocity) from that they originally pursued. 



In the fact that such multitudes of meteors have, during so 

 many and such brilliant displays of November showers as have 

 been recorded, been stolen by the earth from the stream to 

 which they belonged, serves to afford some conception of the 

 immense number of meteors forming the November stream. 

 Yet clearer views will be formed on this point if we consider 

 the evidence we have respecting the length, breadth, and 

 thickness of the cluster, during the passage through which the 

 display is visible. I have not space to dwell here on Adams' 

 investigation of the meteoric orbit. But it is necessary to 

 point out that we must now greatly increase our estimate of 

 the length of the cluster causing the November showers. The 

 recurrence of displays during two or three consecutive years 

 was simply accounted for on the theory of a nearly circular 

 orbit, without assuming for the cluster a length of more than 

 a few millions of miles. Now that we know that the meteor- 

 flight travels in an orbit of great eccentricity, and with a period 

 of 33j years, we know that the portion passed through by the 

 earth in one year is several hundreds of millions of miles away, 

 when the earth next passes through the meteor orbit. Hence 

 the recurrence of displays leads us to estimate the length of 

 the cluster by hundreds of millions of miles, instead of by 

 mere millions. 



Next, for the breadth of the stream. On this point we 

 have no exact information. It is sometimes assumed that the 

 fact that the display may be seen in one hemisphere, while in 



