20 Measurements of the Polarization of the Light from the Moon. 
The most probable values for the polarization (P), meaning by 
that term, the proportion between the intensities of the com- 
ponents of the light polarized in and perpendicular to the plane 
passing through the sun at the several elongations (E) are for 
Mare Crisium— 
EK= P21 Bb yom P=] = 
60° 0°830 110° 0-840 
70 0°815 120 0°890 
80 0°795 130 0-930 
90 0°785 140 0-965 
100 0°805 150 0-980 
Similar, but less numerous measures than those on which the 
above table is based, were made for Mare Imbrium, Mare Sereni- 
tatis, Palus Somnii, and the region between Macrobius and Proclus 
and other parts. The polarization varies with the situation, and 
with the nature of the surface, being in general greater on the 
plains than on the more uneven parts. 
Measurements of the light of the planet Venus made between 
1872, March 12th and April 6th, gave a mean value for the 
polarization of 0°925, of which no regular variation was perceived 
during the progress of the observations, although the change of 
phase which occurred during the interval was considerable. 
May 15th, 1877. 
