1897.] on the Approaching Beturn of the November Meteors, 345 



The Observations now most wanted. 



The immediate lessons we seem to learn from the whole survey are, 

 that while observations upon sporadic Leonids are of little import- 

 ance, the utmost eflforts should be made to determine with more 

 accuracy than has hitherto been possible the radiant point of each of 

 the different parts of the main stream through which the earth will 

 pass in 1899 and 1900, and perhaps in 1898. Every method, both 

 by direct observation and by photography, should be carefully 

 planned beforehand, and employed when the critical opportunity 

 comes. It is of special importance that the observations shall be 

 divided into sections, each extending over a short time — say not more 

 than a quarter of an hour — and that a careful record be kept of the 

 times of the several sections of observations, in order that it may be 

 possible afterwards for the mathematician to compute and allow for 

 the amount of deflection effected by the earth's attraction upon the 

 meteors observed in each of these sections of time. This is a very 

 necessary improvement ujDon the methods used in 1866. It is indeed 

 essential where our aim is to attain great accuracy. Now very 

 much greater accuracy in the observations than that which was at- 

 tained in 1866 is imperatively required for the dynamical calculations 

 which it is desirable that our mathematicians should be enabled to 

 grapple with. 



The matters, then, that are most immediately pressing are : — 



1. To make preparation with the utmost forethought for the 

 observations on the main stream, especially for the determinations of 

 the radiant point in each quarter of an hour. 



2. To make the fullest and most careful observations that are 

 possible upon Tempel's comet. Some of these may probably be by 

 photography. 



3. To compute, so far as can be accomplished with our present 

 materials, the perturbations which the planets Jupiter, Saturn and 

 Uranus have effected on the orbit of the Leonids between November 

 1866 and the present time. 



[G. J. S.] 



