170 Sir J. W. Lubbock on Shootmg Stars. 



every instance of motion in which powers of the velocities 

 above the first may be neglected. Now in the case before us 

 it is clear that no part of the velocity can be constantly the 

 same at a given point for any length of time ; for in propor- 

 tion as the earth recedes from the point, the velocity will 

 become less and less and ultimately vanish. This is true 

 whether the aether be disturbed by the earth or its atmosphere. 

 Hence we shall have 



C=o, C'=o, C"=o. 

 Consequently, substituting f for —crfsdt, we have 



dip dp dp 



"=i' "=^' ^"=i' 

 and udx + vdy-^-vodz an exact differential. 

 Cambridge Observatory, Feb. 8, 1848. 



XXVII. Note on Shooting Stars. 

 Bij Sir J, W. Lubbock, Bart.-^ 



WISH here to correct an oversight in p. 85 of the last 

 Number, where it is im})lied that the same shooting star 

 may be observed to disappear at different instants of time by 

 different ob-servers. It is obvious that if the moving body 

 cease to shine by reason of its entering the shadow of the 

 earth, this event is entirely irrespective of the position of the 

 observer; and therefore if it should be observed by more than 

 one person, such observations will furnish the parallax, and 

 may determine wheti)er this mode of accounting for the dis- 

 appearance of the star is correct or not. It' it has been at- 

 tempted to determine the difference of terrestrial longitude by 

 such observations, probably the materials exist somewhere by 

 which the accuracy of the hj'pothesis can at once be tested. 

 It may possibly however be again observed on the same night, 

 either by the same or different observers, after an entire revo- 

 lution. 



It has been the subject of speculation whether such bodies 

 can owe their origin to violent action at the moon's surface. 

 But observers are, I believe, agreed that the surface of the 

 moon offers no evidence of great agitation. The indentations 

 of the surface remain unchanged, and no phsenomena have, I 



* Communicated by the Author. — The calculation in p. 83 of 5 should 

 stand thus : — 



if7i'=441500 i?=3958 Z)=95,000,000 



log ^-^ =7-36227 :?^ = q= -002302. 



