THE ECLIPSE OF LAST DECEMBER. 
141 
eiding with F. The green zone was the brightest, the most 
uniform, and the best defined. The red zone was also very 
distinct and well defined, while the blue zone was faint and 
indistinct. The green zone was well defined at the summit, 
though less bright than at the base; its form was sensibly 
circular, and its height about 6' or 7'. The red zone exhibited 
the same form and, approximately, the same height as the 
green, but its height was weaker and less uniform. . . . These 
coloured zones shone out upon a faintly illuminated ground 
without any marked trace of colour. If the corona contained 
rays of any other kind, their intensity must have been so feeble 
that they were merged in the general illumination of the field. 
.... The green and red zones were well developed at the 
western as well as at the eastern limb, while the blue remained 
faint and ill defined.” 
From the evidence it appears clear that, as had been sur- 
mised by Young, the gaseous atmosphere containing the 1474- 
matter extends to a height of more than two hundred thousand 
miles from the photosphere ; but hydrogen also is present in 
this deep atmosphere. The well-defined outer limit of the green 
image would seem to show that Respighi had recognised the 
real extension of the atmosphere. Yet it must be admitted 
that some doubts rest on this conclusion. For the recognition 
of a well-defined boundary might have been held to be a 
reason for regarding the apparent limits of the chromatosphere 
as the real limit of the solar atmosphere ; whereas we now see 
that the atmosphere is very far deeper than the sierra. May it 
not well be that, as the observed extension of the sierra indi- 
cates, not the extension of the hydrogen atmosphere, but that 
of the D 3 -matter, so the observed extension of the green zone 
indicates, not the extension of the 1474-matter, but of the 
hydrogen atmosphere ? There is a sudden degradation in the 
brightness of the hydrogen images of the sierra where the D 3 - 
matter is limited ; and in like manner there may be a sudden 
degradation of the 1474 image of the corona where the hydrogen 
is limited. 
Whatever Opinion we form on this point, no doubt can exist 
that circumsolar matter of some sort extends to distances much 
greater than the 6 or 7 minutes mentioned by Respighi. 
The naked eye and low power telescopic views of the corona 
were in some instances obtained under conditions unusually 
favourable. At Bekul Captain Maclear could trace the corona 
to a distance of upwards of 45 minutes from the moon’s limb. 
In the finder the corona had a much smaller extension ; in a 
large telescope six inches in aperture, he could see nothing but 
a bright light round the moon, not much higher than the 
largest of the prominences visible at the moment. Nothing 
