OF THE ZODIACAL LIGHT. 



447 



The observations of Captain Jacobs as communicated to 

 the Astronomical Society by Professor Smyth^and published 

 in the 'Monthly Notices' for December 1862, only afford 

 two instances of observation on the same days as mine, and 

 therefore directly comparable. Of course the value of 

 this comparison will consist more in the observations of the 

 angle of the light with the ecliptic than in that of the 

 length. 



Table IV. 





Date. 



Time. 



R. A. 



Decl. 



Long, 

 of sun 



Length 



Lat. 



Place of 

 Observation. 



1 



1862. 

 June 16. 

 June 16, 

 Julj 16. 

 July 16. 



h. m 

 7 

 7 

 6 40 

 6 40 



h m 



10 5 



9 32 

 12 57 



11 12 



12 30 N. 

 14 



534S. 



5 



/ 



85 I 



85 I 



113 37 



"3 37 



1 

 64 4 



55 24 

 82 19 



53 52 



i 



43 



— 41 



43 

 4 



/ 

 26 30 S. 



3 17 

 29 52 



35 4S. 



' „, 

 34 oW. 



82 35 E. 



55 19 

 20 30 E. 



Column 5 contains the longitude of the sun. The first 

 and third lines contain the observations made by Captain 

 Jacob, the second and fourth those made by myself. All 

 the other observations communicated by Professor Smyth 

 fall within the period over which my observations extend ; 

 but none are made on the same days, except those above 

 cited. His lengths are much greater than mine; but 

 neither of mine on the particular days included the outer 

 envelope. 



It appears evident from all the observations, and also 

 from those of Captain Jacob, that great changes occur in 

 the length of light visible, whether these be due to obstruc- 

 tions to vision offered by our own atmosphere or to actual 

 differences. The same peculiarity is notable in the observa- 

 tions made during the American Naval Expedition to Japan. 

 The observer, the chaplain of the ship, often delineates on 

 his charts lengths which I have never seen approached, 

 such as observations of the morning light visible before 

 midnight ; but others of his charts show lengths of 55° only. 



