Burton — Note on the Zodiacal Light. 223 



point of intersection being nearly three degrees. (Sketch 2.) Within 

 this luminous region there appeared to be a distinct nucleus, the 

 intensity of the Light increasing somewhat abruptly toward the 

 centre from both sides, and forming a tolerably defined central 

 cone, five or six degrees broad at the horizon, and twenty-five 

 degrees in length. At an elevation of ten degrees from the horizon 

 the central region of the Light appeared to exceed in intrinsic bright- 

 ness every part of the Milky Way, except, perhaps, the narrow stream 

 in Argo. 



Date. — 1875, February 5"^ 7^ local mean time. 



Place of Observation.— Lat. 3° S. Long. 70° E. 



Form of Light. — Lieutenant Neate, Chief of the Eodriguez Transit 

 of Yenus Expedition, observed a short branch or spur diverging at a 

 small angle from the base of the principal mass of Light on the south 

 side, as shown in Sketch 3. The spur was very faint when compared 

 with the neighbouring luminosity, but was distinctly seen by another 

 observer when Lieutenant ]S"eate drew his attention to it. 



Late. — 1875, Eebruary, 1"^ V\ ± local mean time. 



Place of Observation.— Lat. 2° 30' IS". Long. 73° E. 



Spectrum. — The pocket spectroscope used on 1875, January 2*^, 

 showed a faint line, estimated to be near solar E. It was separated, or 

 nearly separated, from a short continuous spectrum by a narrow dark 

 band. The continuous spectrum faded gradually into darkness, with 

 increasing refrangibility. This compound spectrum varied in brightness, 

 but did not change its character when the instrument was swept round 

 in a small circle parallel to the horizon at an elevation of 15° or 20°, 

 except when it received light from any part of the Milky Way, which 

 added its spectrum to the other, and produced confusion. 



The brightness of the Zodiacal Light Spectrum was far greater when 

 the instrument was directed toward the bright central region of the 

 luminous cone-shaped haze than when it received light from any other 

 part of the sky. (Sketch 4.) 



Polarization. — With the Savart polariscope bands were distinctly 

 seen, especially when the principal plane of the Mcol prism was nearly 

 at right angles to the axis of the Zodiacal Light, and the disposition of 

 the bands indicated that the plane of polarization was inclined about 

 75° to that line. 



This result was confirmed by the subsequent obaervation with the 

 simple jSTicol prism, made independently by the same observers (Messrs, 

 Ideate and Burton). 



Date.—\%15, Februai-y 11. 



Place of Observation. — At sea, near Trincomalee, Ceylon. 



JBrightness.—^ThQ Zodiacal Light began to be visible less than half 

 an hour after sunset, and despite the neighbourhood of the crescent 

 moon. 



