A. W. Wright—Polarization of the Zodiacal Light. 457 
Ly] 
_ We must conclude, then, that the light is reflected from matter 
m the solid state, that is, from innumerable small bodies revolv- 
ing about the sun in orbits, of which more lie in the neighbor- 
hood of the ecliptic than near any other plane passing through 
the sun. Although such a cause for the zodiacal light has 
often been assumed as probable, no satisfactory proof of it 
has hitherto been found, and the establishment of the fact of 
polarization was necessary to its confirmation, since spectro- 
scopic appearances alone leave it uncertain whether the matter 
1S not self-luminous. 
_if these meteroids, as there is no good reason to doubt, are 
Similar in their character to those which have fallen upon the 
earth, they must be either metallic bodies, chiefly of iron, or 
stony masses, with more or less crystalline structure, and 
_ In order to ascertain whether the proportion of polarized 
light actually observed approached in any degree what might 
be expected from stony or earthy masses of a semi-crystalline 
character, with a granular structure, and surfaces more or less 
rough, a large number of substances ing these charac- 
teristics was subjected to examination with a polarimeter. For 
is ‘purpose the apparatus already described was employed, 
there being added to it a support for the object, with a horizon- 
* “Ueber die Natur der Cometen,” p. 79, et seq. Abstract in this Journal, 
IH, vol. iii, p. 476. 
