184 Field Museum of Natural History — Geology, Vol. III. 



from noon to 6 p. m. 124, and from 6 p. m. to midnight 60. Hence it 

 seems probable that some of the diminution in the number of falls 

 is due to lack of observers, although Newton* seemed to conclude 

 from studies of the orbits of the morning falls that lack of observ- 

 ers had little to do with their scarcity. Lack of meteorites during 

 morning hours may also be due in part, as Newton suggested, to the 

 fact that such as have retrograde motion are more likely to be burned 

 up by the greater velocity with which they strike the earth's atmos- 

 phere. This increase in velocity is not so great as might be supposed 

 since Lowell has shown f that it cannot exceed 2.66 miles per second. 

 Yet Pickering J thinks it is sufficient to destroy all that have retro- 

 grade motion, or that the velocity of such as have retrograde motion 

 would be higher than any that has yet been recognized. It is not 

 clear how such an increase would be very apparent if this increase at 

 most is only 2.66 miles per second. On account of the above proba- 

 bilities Pickering is of the opinion that most if not all of the meteorites 

 which fall in the morning hours are moving at so slow a speed that 

 they are overtaken by the earth. Schiaparelli, who gave the matter 

 much study and to whom we are indebted for extensive researches 

 in the relations between comets and meteors, concluded that many 

 meteorites had hyperbolic velocities and hence must come from the 

 world of fixed stars rather than from comets or the solar system. || 

 Newton assigned to the stone of Stannern a velocity of 45 miles per 

 second, and concluded that most meteorites are allied to short period 

 comets in their velocities. § Pickering ^[ regards it doubtful whether 

 any stony meteorites move fast enough to be accredited with cometary 

 velocities. 



The hourly falls of the writer's table are shown plotted in Plate LIX. 

 It will be observed that the peak of the falls occurs at 3 p.m. Picker- 

 ing has shown ** that other things being equal the greatest number of 

 meteorites would be expected when the Earth's quit is highest above 

 the horizon and that this occurs, for the northern hemisphere, longi- 

 tude 90 , at 3 p. m., May 6. This high point agrees with. that of the 

 greatest number of meteorites, for they are most numerous in May 



* Am. Jour. Sci., 1888, 3, 36, 10. 

 t Science. N. S., 1909, 30, 339. 

 % Popular Astronomy, 1910, 18, 264. 



|| Entwurf einer Astronomischen Theorie der Sternschnuppen. Boguslaw- 

 ski's translation, 1871, p. 228. 



§ Am. Jour. Sci., 1888, 3, 36, 11, and 13. 

 IT Popular Astronomy, 1910, 18, 276. 

 ** Op. cit., p. 272. 



