254 



NATURE 



{July 12, 1888 



earth's orbit. There should be about as many orbits 

 having retrograde motions as direct motions. Hence the 

 absolute quits of all stones coming into and hence, by 

 hypothesis, coming through the air, should be symmetric- 

 ally distributed in their longitudes relative to the sun. 

 At least there should be as many absolute quits in the 

 G-hemisphere as in the O hemisphere (Fig. 1). Take 

 account now of the earth's motion and locate the relative 

 quits. All these stones whose absolute quits lie outside 

 of the circle T T will have their relative quits in the 

 G-hemisphere. Upon the hypothesis of parabolic orbits 

 and of an equable distribution of the absolute quits over 

 the celestial sphere the number of relative quits in the 

 G-hemisphere should be to those in the Q-hemisphere 



as 1 + cos — : 1 — cos — , or as 17: 3. The relative quits 



4 4 



should then be very much more numerous in the G-hemi- 

 sphere than in the Q-hemisphere. 



Furthermore, suppose that the heavens visible at a given 

 time and place, are divided by a vertical circle into two 

 halves ; and suppose that this vertical circle is at right 

 angles to the plane containing the zenith and the earth's 

 quit and goal. That half of the visible heavens that lies 

 towards the earth's goal may be called the goal-half, the 

 other half may be called the quit-half of the visible 

 heavens. In any given period there should evidently be, 

 under the several hypotheses stated, many more stones 

 coming into the air and reaching the ground directed 

 from the goal-half than there should be directed from the 

 quit-half of the visible heavens. Still further, since this 

 proposition applies to any epoch whatever, we may apply 

 it to 116 periods covering the times of the 116 stone-falls, 

 that is, to the 116 stone-falls themselves Many more of 

 these should (under the hypotheses stated) have come 

 from the goal-half than from the quit-half of the visible 

 heavens. 



If, then, the relative quit of each of these 116 stones is 

 supposed to be carried around in azimuth 1 8o°, the altitude 

 being unchanged, the 116 distances from each new place 

 of the quit to the earth's quit for the epoch of the fall 

 should, in the average, be decidedly less than the cor- 

 responding 116 distances from the actual relative quits to 

 the earth's quit. This should hold true (under the hypo- 

 theses stated) no matter what. causes below the air may 

 have occasioned the selection of the 116 epochs. The 

 fact that more persons are abroad in the evening hours 

 from 6h. to ioh. p.m., than in the corresponding morning 

 hours, 2h. to 6h. a.m., may well cause that more stones 

 should be secured in the evening than in the morning 

 hours. In the evening hours the earth's quit is above the 

 horizon ; in the morning hours the earth's goal. It might 

 easily be that we should for this reason get more stones 

 of direct than of retrograde motions. But the 'above 

 criterion is entirely independent of any such principle of 

 selection of the epochs. A change of the azimuth of the 

 quits through 180 should cause a larger number of them 

 {under the hypotheses stated) to approach the earth's quit 

 than to recede from it. 



I have marked off upon the working sheets the position 

 180 in azimuth from each of 1 15 relative quits, the altitude 

 being unchanged, and measured the several distances 

 from the earths quit. (One fall, Nedagolla, was unavail- 

 able). The following is the result. In 44 cases the 

 meteor's quit by the change approaches the earth's 

 quit ; in 70 cases it approaches the earth's goal ; in one 

 it remains unchanged. That is, instead of a very large 

 majority of the quits moving towards the earth's quit we 

 have nearly two-thirds of them moving the other way. 

 In the reversed position, moreover, we should have had 

 38 absolute quits in the G-hemisphere instead of 7. These 

 numbers show very decidedly that the hypotheses made 

 above are not 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 twenty-five of the quits in Fig 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 considering. 



We are now in position to consider the other ninety- 

 four stone-falls. In Fig. 2, the construction of which is 

 similar to that of Fig. 1, the stars mark the zenith points 

 for each time and place of the ninety-four falls. A grouping 

 is at once noticeable. They are nearly all in the northern 

 hemisphere, since the observing peoples live there. Those 

 stars in the hemisphere of which S is the pole, that is 

 between the two lines P P and P P, are evidently daylight 

 stone falls, since S is above the horizon for each case. 

 These constitute about seven-eighths of the whole 

 number. 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 fall is usually the 

 hearing of the detonation two or three minutes after the 

 fireball has disappeared. Hence, daylight stone falls are 

 those whose directions are less likely to be observed, and 

 these ninety-four 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 after- 

 noon stone-falls, the latter forenoon stone-falls. Now the 

 habits of the urban population 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 m my people are there 

 abroad in the forenoon as in the afternoon. 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 O-hemi- 

 sphere. The contrary being the fact of experience we 

 may reasonably say that the ninety-four stone-falls, about 

 which we know comparatively little, seem decidedly 

 to follow the same laws as the 116 falls about which we 

 know so much more. 



This conclusion is greatly strengthened if we take 

 account of the effect of the earth's attraction in carrying 

 the meteor's quit toward the zenith. Any stone must be 

 moving downward when it enters the air. But the earth's 

 attraction must change the direction of its motion during 

 the approach to the earth. Hence the region of the 

 heavens from which a stone can approach the earth is not 

 bounded by the actual horizon, but by a curve which may 

 be treated as a depressed horizon. This depression of 

 the horizon is far greater toward the quit than toward the 

 the goal side of the horizon. The maximum depression 

 for a stone moving in a parabolic orbit is about 1J°. It 

 hence follows that when the zenith is more than 73 and 

 less than 90 from G, both the points G and Q are above 

 the depressed horizon, and therefore that the 14 falls 

 whose zeniths are between these limits, that is, are be- 

 tween the circles A A and PEPS, Fig. 2, should be left 

 out of the count. The corresponding region on the Q- 

 hemisphere is less than one degree in breadth, and con- 

 tains one zenith point. We have left only 20 falls when 



