1900 - 1 .] Mr Thomas Heath on Photographs of the Corona. 399 
in obtaining photographs which for beauty of detail have not since 
been much, if at all, improved upon. Reproductions of drawings 
made from the combined negatives of each of these observers 
will be found in vol. xli. of Memoirs of the Royal Astronomical 
Society . A glance at these two pictures will show their remark- 
able resemblance, and even careful examination fails to show 
differences between them in more than a few of the minuter 
details. In each the Corona extends to rather less than a solar 
diameter from the limb. As to the drawings made by hand from 
visual observations with telescopic assistance — and this is also true 
of every eclipse observed in this way — there is nothing so remark- 
able as their dissimilarity. On the other hand, Captain Tupman’s. 
drawing depicts the Corona extending to fully 1J diameters 
from the limb, as compared with less than one diameter of the 
photographs. 
Somewhat similar has been the result of the 1900 eclipse. 
None of the photographs, or reproductions of photographs, which 
have come under my notice, show so far-reaching a Corona 
as is shown in what I quite believe is a most faithfully executed 
drawing. I refer to the drawing by Dr A. Wolfer of Zurich 
and two colleagues, published in the Archives des Sciences 
Physiques et Naturelles of Geneva. While in my photographs the 
Corona reaches outwards about a diameter and a half, Dr Wolfer’s 
drawing shows it extending more than two diameters, and a very 
striking peculiarity of the drawing, as compared to the photographs,, 
is that the eastern extension, instead of coming to a point, is 
spread out to a shape very similar to the western extension. 
It would appear, therefore, that photography, as at present 
practised, has its limitations in the direction of coronal work, and 
by no means does away with the usefulness of trustworthy draw- 
ings. These limitations are particularly felt in such an eclipse as 
that of May 1900, on account of the short duration of totality 
and the general brightness of the sky. There seems no reason to 
suppose, however, that photographs of the Corona could not be 
taken in a long total eclipse, of say five minutes’ duration, which 
would show the extensions as far out as they were visible to the 
eye, unless we are to adopt the suggestion which has been made, 
that the outermost regions are less rich in actinic light, as compared 
