﻿484 Intelligence and Miscellaneous Articles. 



tion C of the same solution may be found by the formula C= AE, — 

 that is, by simply multiplying the coefficient of absorption of the 

 substance (which has once for all been determined) by the coefficient 

 of extinction of the solution (to be measured on the spectrum-appa- 

 ratus), The coefficient of extinction is the negative logarithm of the 

 luminous intensity which remains after traversing a layer of the ab- 

 sorbing medium a centimetre in thickness. — Berichte der Deutschen 

 Chemischen Gesellschaft , No. 6, 1871. 



ON THE ZODIACAL LIGHT. BY A. C. RAYNARD, ESQ. 



The conviction that the accumulation and comparison of evidence 

 on a subject so interesting and yet so little understood as the zodiacal 

 light cannot but be useful, induces me to submit the following ob- 

 servation to the notice of the Astronomical Society : — 



On the evening of the 1 9th of December last the detachment of 

 the Eclipse Expedition encamped at Agosta had an opportunity of 

 examining a particularly brilliant display of the zodiacal light, 

 stretching to some 80° from the sun's place : its contour was of a 

 somewhat conical form, blunted at the apex, the semi- vertical angle 

 of the cone being about 1 2°. Its light was apparently white, and 

 was undistinguishable in point of colour from the light of the Milky 

 Way, which also shone out with considerable distinctness upon the 

 night in question. I was anxious to see if any polarization could be 

 detected, and for this purpose made use of a Savart, and at first 

 thought that faint lines were visible, indicating polarization in a 

 plane through the sun ; but not being at all sure of my observation, 

 I asked Mr. Burton, who was formerly assistant to Lord Rosse, and 

 has very keen eyesight, to look through the instrument : he at once 

 said that he distinctly saw bands brightest when the Savart was 

 turned so that the direction of the bands passed through the sun, 

 and that the centre band was black ; he also saw the bands perpen- 

 dicular to the sun's direction, but could not determine the nature of 

 the centre one. I should mention that the Savart was so set as to 

 give a black centre when the bands were parallel to the plane of po- 

 larization. 



I then asked Mr. Burton to see if he could detect any bands upon 

 the sky away from the zodiacal light, but he was unable to do so 

 even at 90° away from the sun's position. 



I again took the instrument, but was unable to see any bands 

 myself. On the next night the zodiacal light was again visible, but 

 with considerably less brilliance than before. Father Secchi ob- 

 served it with a Savart, and thought that he detected faint bands, 

 but said that he could not be sure of his observation. 



If other observations should confirm those of Mr. Burton, we shall 

 be in possession of proof, not only that the zodiacal light consists of 

 matter which reflects the sun's light, but that 



(1) That matter exists in particles so small that their diameters 

 are comparable with the wave-lengths of light ; or 



(2) It consists of matter capable of giving specular reflection. — 

 Monthly Notices of the Royal Astronomical Society, March 10, 1871. 



