160 
NATURE 
[Fune 29, 18715 

LETTERS TO THE EDITOR 
[Zhe Editor does not hold himself responsible for opinions expressed 
by his Correspondents. No notice is taken of anonymous 
communications. | 
The Eclipse Photographs 
In his letter published in NATURE on the Ist of June, and to 
which Mr. Brothers courteously replies in your issue of the 15th, 
the writer briefly touched upon four different points bearing on 
the value of the eclipse photographs. Those points are :—Ist, 
The possibility in a comparatively cloudless sky of a luminosity 
akin to that represented under the name of the corona on page 
370 of the number of NATURE issued on March 9, but caused 
only by moisture in our atmosphere, as illustrated by his instance 
of what he termed a lunar halo; 2ndly, The presence of a 
luminosity on what he apprehends should have been the dark 
disc of the moon, as represented in the photograph of the 
American observers at Cadiz ; 3rdly, The indifferent definition 
of the published photograph ; and 4thly, The evidence as pre- 
sented by the photograph of the identity of the coronal rifts. 
Referring to the first of these points, Mr. Brothers ‘fails 
altogether to see the connection between the solar corona and a 
lunar halo.” If the term halo, as applied to any appearance 
pertaining to the moon, is confined to the ring of light so 
frequently to be observed apparently surrounding the lunar disc, 
the writer would substitute the word ‘‘luminosity” for halo. 
The appearance he alluded to resembles Mr. Brothers’s wocdcuts 
of the corona already mentioned, more than anything else to 
which he can compare it, and in common phraseology may be 
described as a patch of light surrounding the apparent position 
of the moon, extending from it to a distance varying from about 
one degree to two or two and a-half, and having an irregular or 
rifted outline. The phenomenon in question was observed by the 
writer when the atmosphere was in such a condition that no trace 
of cloud whatever was visible for a distance round the moon 
of some thirty or forty degrees. He mentions this merely to show 
that even when no visible condensation of moisture is present, 
an appearance—attributable to nothing but atmospheric moisture, 
and analogous to what is termed the solar corona—is not to be 
regarded as out of the common, and nothing to be wondered at. 
Touching the second point, Mr. Brothers would seem to be of 
opinion that a solar corona may be seen even when the dark disc 
of the moon intervenes between it and the observer’s eye ; for he 
says of the luminosity in question that if caused by our atmosphere 
it would extend all round and all over that disc. The point at 
issue here is a very simple optical question, in the discussion of 
which space would be merely wasted, and in reference to which 
the writer would simply reiterate the opinion he has already ex- 
pressed, that the luminous appearance as seen extending on to 
the disc of the moon in the Cadiz photograph, is (if it were visible 
outside the camera) attributable to nothing but the influence of 
the terrestrial, or of a lunar atmosphere. Whilst speaking of the 
American observer’s picture, he would remark in answer to two 
observations by Mr. Brothers, first, that he is not in “ possession 
of exclusive information ” concerning the circumstances of its pro- 
duction ; and secondly, that he does not assume that it was taken 
under conditions less favourable than those prevailing at Syracuse. 
He does, however, assume that that photograph either 
represents only the phenomenon to which the instrument used 
in its production was directed, or that it represents some- 
thing in addition to that phenomenon. If its representation 
is confined to the phenomenon, then upon the grounds al- 
ready shown, he considers that what is called the coronal light 
in the Cadiz picture not only may be, but most certainly is, in 
part at any rate, merely the result of atmospheric moisture. If, 
however, the American observers were unfortunate enough to re- 
present in their photograph a luminosity not belonging to the 
eclipse at all, then he considers that what did belong to the 
eclipse is not distinguishable in their picture from what did not. 
In short, whether the Cadiz picture does or does not represent 
only what itshould do, the writer is of opinion that any evidence 
it can afford respecting the identity of the coronal rifts must be 
other than satisfactorily conclusive. 
Concerning the third point, namely the ‘‘ indifferent defini- 
tion,” to which he directed attention, Mr. Brothers admits the 
validity of his remarks, so far as Syracuse picture No. 5 is con- 
cerned ; and this picture, it may be observed, Mr. Brothers 
would seem to consider the best of his series, inasmuch as it is 
the only one procurable of the opticians in Manchester, and also 


is the one selected for an engraved representation in the pages of 
NATURE. 
Respecting the last of the four points on which the writer has 
taken the liberty to remark, viz. the evidence afforded by the 
photographs of identity in the coronal rifts as seen at Cadiz and 
Syracuse, he is of opinion that he has already said sufficient to 
justify his observation that that evidence is not ‘‘ satisfactorily 
conclusive.” If, however, Mr. Brothers should entertain a dif- 
ferent opinion, and the Editor of Nature think the matter 
worthy of further space, he will make a few other remarks, look- 
ing at the subject from an altogether different point of view. 
In conclusion, the reader should be reminded that the subject 
under discussion is not the astronomical question—Is the sun sur- 
rounded by a medium which is illuminated by his rays and 
rendered visible under favourable circumstances to the eye of a 
terrestrial observer? but, assuming this to be the case—Is the 
luminosity indicated in the photographs under consideration a 
representation of that medium or is it not ? 
The writer dors not doubt the existence of such a medium 
round the body of our great luminary (‘hough, assuming it, ought 
there not to be some trace of it visible above the western horizon, 
immediately after sunset ina dry climate ?), but he does doubt 
whether the patch of light depicted in the photographs of the late 
solar eclipse is in the main other than a phenomenon of terrestrial 
meteorology. D. WINSTANLEY 
The 
Mr. Proctor entirely misunderstands me if he thinks that 
my criticism on his account of the solar parallax had reference to 
any failure on his part to give prominence to the discussion 
between Mr. Stone and myself, or to correctly apprehend that 
discussion. To point out all the imperfections and inaccuracies 
in his account would take a whole column of NaTuRE, and I 
have neither the time nor the disposition to make such a display 
of the accidental errors of a fellow-worker in the astronomical 
field. But, if Mr. Proctor desires it, I will constitu'e him judge 
in his own case in form and manner as follows ; I will send him 
privately the list of specifications on which my criticism was 
founded. If, in his opinion, this list fails completely to sustain 
the proposition that his history of recent researches on the solar 
parallax is ‘‘imperfect and inaccurate in a remarkable degree,” 
he is to publish it with any defence he chooses to make. Other- 
wise he may keep it for his own private use in case he brings out a 
second edition of his work. The kind spirit in which he has 
taken my remarks is highly appreciated, and I shall be happy to 
hear from him privately on the subject. Simon NEwcomsB 
Solar Parallax 
Halo in the Zenith 
AT 20 minutes to 6 p.M. on Saturday roth inst., I witnessed 
a natural phenomenon which I understand is very unusual. It 
was a portion of a halo around the zenith. Take the zenith <s 
centre, and with a radius of 20° describe an arc of 120° parallel 
to the horizon, and having 60° on each side of due west. This 
gives the position in the heavens, as nearly as I could determine, 
using no other means of observation except my eyes. The con- 
vex surface was red, concave blue. Other colours were also 
apparent, and were very distinct towards the centre of the are ot 
120°, becoming much diluted at a greater distance. The homs 
of the arc gradually faded away amid the cirri with which the 
whole sky was covered, its blue colour being only partially ob- 
scured. You could tell at a glance that the zenith was the centre 
of the hale. The phenomenon only continued five minutes 
from the time I first saw it, until it disappeared altogether. 
It has been suggested to me that probably the azimuth of the 
sun and that of the centre of arc of 120° coincided. I think this 
is very likely, but I did not note it particularly at the time. The 
wind was easterly, and the sun shone brightly where I was 
standing. If any of your numerous correspondents would favour 
me with an explanation of the above I would be greatly obliged. 
No other halo or portion of a halo was visible at the time. 
R. M. BARRINGTON 
Fassaroe, Bray, Co. Wicklow, June 26 


What is Yellow Rain? 
THE letter of Mr. A. Ernst in NaturE, May 25, ona recent 
case of ‘‘ yellow rain,” possesses considerable interest to all who 
have paid any attention to early prodigies ; because his deter- 
