BuRTOiSr — Note on the Zodiacal Light. 221 



Date. — 1874, August S^" 8^ local mean time. 



Place of Oiservation.—RM.8. " Shearwater." Lat. 28° 4'S. ; Long. 

 58° 46' E. 



Spectrum. — The bright line forming the less refrangible boundary 

 of the visible spectrum was well observed, being much more distinct 

 than on former occasions. This line would be more accurately de- 

 scribed as a narrow bright band, with tolerably well-defined edges ; 

 especially that which is least refrangible. Its centre has a wave 

 length of 5670 seventh-metres, according to the measures obtairied. 

 The dark streak at 5355 ± was not seen, there being barely time for 

 the measures of the bright band, as clouds rapidly formed and ob- 

 scured the Zodiacal Light. The existence of the bright band was 

 verified by one of the ship's officers, Lieut. Pullen, E.N., who kindly 

 gave me most efficient assistance on the occasion. 



Date. — 1874, August 5'^ 6*^ 50"^ local mean time. 



Flace of Oiservation.—R.'K.Q. " Shearwater." Lat. 23° 45' S. ; 

 Long. 58° 35' E. 



Spectrum. — The narrow bright streak was again seen, and its place 

 determined, but the instrument seems to have been deranged between 

 the observation of the Zodiacal Light and of the standard spectrum 

 — in this case the solar spectrum. The measure has been rejected. 

 There was a very faint and ill-terminated extension of light on the 

 less refrangible side of the bright band, which may have been due to 

 some remains of twilight, or to the near neighbourhood of the planet 

 Yenus, which was then very brilliant, to the region under inspection. 

 A dark streak, apparently somewhat less refrangible than solar E, 

 was distinctly seen. The breadth of this streak was estimated as equal 

 to about 40 units of Angstrom's scale. 



Date. — 1874, August W 7^. Hour not noted at the time, but 

 inserted here from recollection. 



DIace of Observation. — Port Louis, Mauritius. 



Spectrum. — The bright band seen. The measures give 5690 seventh- 

 metres as its wave length. 



Date.— lS7i, August 11^ 8^. 



Place of Observation. — Port Louis, Mauritius. 



Spectrum. — Measure largely in error, some slip of the clamp or 

 record carrier having probably occurred. 



Polarization. — Lieut. ISTeate, the chief of the Eodriguez Transit of 

 Yenus Expedition, was able to detect bands parallel to the principal 

 axis of the luminosity, while making use of the Savart arrangement 

 before mentioned. I could not see them, being fatigued with the 

 previous spectroscopic work. 



The bands seen indicated, according to Lieut. ]!^eate's remarks, a 

 slight degree of polarization in planes parallel to the axis of the Light. 



