Meteorites to the Earth's Orbit. 11 



true. The principle of selection is not entirely below the air, 

 and the numbers testify so markedly against that hypothesis 

 that I feel warranted in adding that the cause is mainly either 

 above the air, or in the air. 



Between the first and second causes named the materials 

 used for the present discussion do not furnish a positive critical 

 test. But if, as I believe, the Stannern stone came from the 

 south, we have at least one instance of stones coming into the 

 air with a velocity of nearly, or quite, 45 miles a second and 

 reaching the ground in solid form. About 25 of the quits in 

 figure 1 imply velocities of not less than 25 miles a second on 

 entering the air. Large velocities do not seem to be entirely 

 fatal to the integrity of the meteorites. I believe that the first 

 cause was the dominant one rather than the second, yet for a 

 crucial test of the two causes, if one can be found, we must 

 look to a class of facts other than those we have been consider- 

 ing. 



We are now in position to consider the other 94 stone-falls. 

 In figure 2, the construction of which is similar to that of fig- 

 ure 1, the stars mark the zenith points for each time and place 

 of the 94 falls. A grouping is at once noticeable. They are 

 nearly all in the northern hemisphere, since the observing peo- 

 ples live there. Those stars in the hemisphere of which S is 

 the pole, that is between the two lines PP and PP, are evi- 

 dently daylight stone falls, since S is above the horizon for each 

 case. These constitute about seven eighths of the whole num- 

 ber. The reason for this predominance is manifest. In the 

 night men see the fireball or the train, whereas in the day the 

 first intimation of the stone-iall is usually the hearing of the 

 detonation two or three minutes after the fireball has disap- 

 peared. Hence, daylight stone-falls are those whose directions 

 are less likely to be observed, and these 94 falls are the ones of 

 which the directions are unknown. 



It will also be seen that there are nearly twice as many in 

 the Q-hemisphere as in the G-hemisphere ; that is, there are 

 nearly twice as many that fell when the earth's quit was above 

 the horizon as there were when the earth's goal was above the 

 horizon. In general, the former were afternoon stone-falls, the 

 latter forenoon stone-falls. Now the habits of the urban pop- 

 ulation have not much to do with these daylight meteors, for 

 the fireballs were not seen. The accounts come from the 

 country, where the stones in general have fallen, and about as 

 many people are there abroad in the forenoon as in the after- 

 noon. If stones came to the ground as often from retrograde 

 as from direct orbits we ought apparently to have had very 

 many more zeniths in the G-hemisphere than in the Q-hemis- 

 phere. The contrary being the fact of experience we may rea- 



