NOTE ON THE TOTAL ECLIPSE OF THE MOON. 167 
seen at all, and in the open air many persons failed to discover 
it. With an opera glass the nebulous spot was resolved into a 
well-defined disc of the proper form and dimensions, but still 
very faint and dingy. 
That this unusual obscurity of the moon is not to be 
explained by the central character of the eclipse and consequent 
deep immersion of the moon in the earth’s shadow, will clearly 
appear when it is stated that in the eclipse of August, 1877, 
above referred to, the immersion of the moon in the earth’s 
shadow was still deeper than on tbe late occasion ; and, further, 
that in the recent eclipse the unusual obscurity of the eclipsed 
portion was such as to attract notice even before the immersion 
was complete — indeed it was not until within a few minutes of 
totality that the dark part of the moon could be distinguished 
with the naked eye. 
A consideration of the causes of these great differences in 
tbe visibility of the eclipsed moon raises of necessity the previous 
question of the reason why the eclipsed moon is visible at all ; 
and it is chiefly because there appear to me to be reasons for 
doubting the correctness of the views commonly accepted on this 
matter that this note is offered. 
The following quotation from a newspaper article published 
in anticipation of the late eclipse may be taken as representing 
the current opinion : — 
“ Even after the immersion in the shadow some of the rays of 
the sun’s light are reflected through our atmosphere on the lunar 
surface, just as we receive the rays after the sun has really 
descended below our horizon The explanation of the 
visibility or the partial or total disappearance was first satisfactorily 
given by Kepler, who showed that if the part of the terrestrial 
atmosphere through which the solar rays pass be tolerably free 
from vapour, the red rays are almost entirely absorbed, leaving the 
blue rays, which give too feeble an illumination to render the moon 
