242 
the overwhelming intensity of the relatively white 
light of the middle of the sun’s disc had been screened 
oft by the interposing moon; but it would have been 
impossible to perceive the red colour, intense though 
it was, had it not been for the perfection of my 
reducing glass, which, while it reduced the intensity, 
preserved the natural colour of the sun’s light. 
Before the most striking phenomena of the central 
phase began to crowd across my view, I noticed the 
beginning of the phenomenon which most impressed 
me when witnessing the eclipse of May, 1882, in 
Egypt. In the last moments before totality the rate 
of extinction of light was very great, and 1 compared 
it with that which would take place in a well-illu- 
minated room when a shutter is rapidly drawn down 
over the window. In the case of the 1882 eclipse 
the shutter was drawn quite down, and nocturnal 
darkness was produced with the appearance, not only 
of all the principal stars, but also of an unsuspected 
comet in the immediate vicinity of the sun. In the 
case of the present eclipse the shutter was at first 
being drawn down quite as rapidly, but it stopped 
short, and was almost immediately pulled up again. 
I have no doubt whatever that if the eclipse had been 
total, it would have been a very dark one. 
The central phase was now close at hand, and the 
appearance of the luminaries changed so rapidly that 
it was impossible to time the changes. After the light 
of the whole solar crescent had become quite red, my 
attention was attracted to the lower (S.E.) luminous 
cusp, which seemed to become indented by black 
bands or teeth. Then the upper (N.W.) cusp showed 
a similar phenomenon; and, almost in a moment, the 
black teeth spread over the whole crescent, which 
then offered a magnificent spectacle. The bands or 
teeth did not span the crescent always by the shortest 
path, but they crossed and intersected each other like 
a crystallisation. There was, however, but little time 
to study them. Very quickly the dark disc of the 
moon advanced and pushed the beautiful network over 
the eastern edge of the sun, which it totally obscured, 
and, apparently at the same moment, the network 
reappeared, coming over the western edge of the sun, 
attached to the black limb of the moon, and at the 
same time held by the limb of the sun. In a few 
moments the uncovered crescent of the sun had in- 
creased so much that the delicate lacework could no 
longer bear the tension; it parted and disappeared 
instantly, while at the same moment the dark limb 
a the moon recovered its perfect smoothness of out= 
ine. 
The central phase of the eclipse was over, and I 
could not say that I had seen either a total eclipse or 
an annular one, but I had witnessed a very remark- 
able natural phenomenon. i 
All the phenomena were so astonishing and followed 
each other so closely that it was impossible to pay 
attention to every detail. The two crescents, the dis- 
appearing and the reappearing one, seemed to be 
situated diametrically opposite to each other. T per- 
ceived nothing on the upper (N.) or the lower (S.) edge 
of the common disc, but there might have been a 
thread of light or a string of minute “beads” on one 
or both of them; and, consequently, I cannot say if 
the light of the disappearing crescent passed round 
the northern or the southern limb of the common 
disc and so preserved continuity between the departing 
and the arriving crescents, or if it passed round at all. 
All that I saw was the extinction of the departing 
crescent, and, post saltum, the illumination of the 
arriving crescent. 
When the moon is in conjunction and the sun is 
behind it, the mountains cut by a tangential surface 
cannot be very evident, because they can only be the 
NO. 2219, VOL. 89] 
NATURE 
[May 9, 1912 
summits of the very loftiest peaks. The valleys are 
wholly masked. My binocular, the magnifying power 
of which is only twofold, shows the mountains and 
valleys beautifully when the moon is in quadrature, 
but during the eclipse it made the edge of 
the lunar disc appear as a smooth and con- 
tinuous line. The mountains were perfectly invisible 
on it; yet what we take to be their images were 
enormous. The phenomenon is not a subjective or an 
instrumental spectre, because it is seen by everybody, 
with every kind of instrument and without any in- 
strument at all. It is a reality; it must therefore be 
due to a substantial cause, and to one which can be 
shown to be capable of producing the effect. May not 
this substance be the often suggested lunar atmo- 
sphere; and, if so, what is its exact specification ? 
May 3. J. Y. BucHANnan. 
The Distastefulness of Anosia plexippus. 
REFERRING again to the above topic (NATURE, 
December 21, 1911), I wish to make clear my position 
on the subject. Mr. Pocock’s experiments indicate 
that Anosia plexippus is distasteful to many birds, 
but it is desirable to know whether or not Basilarchia 
archippus is palatable to birds, and it is absolutely 
necessary, before the usefulness of this case of mimicry 
can be shown, to know that North American birds 
eat some butterflies, but scarcely, if at all, molest 
these two forms. 
My former letter was prompted by the evident 
assumption in the note of October 12 that the case 
was necessarily one of useful mimicry. 
The only case I know of North American birds 
taking butterflies to any extent only serves to empha- 
sise the lack of attractiveness of butterflies to birds. 
In this case (referred to by the observer in Nature, 
February 15, 1912) only five out of forty-five species 
of birds observed could be found by direct observa- 
tion and stomach examination to eat the Eugonia 
californica, which occurred in such countless numbers 
as to constitute a pest. Two species of fly-catchers 
captured them to some extent, meadow larks were 
shown to take them sparingly, and the omnivorous 
blue-fronted jay, so far as the evidence went (two 
stomach examinations) ate the butterflies to the 
extent of one-third of their food. But the only avian 
species which was shown generally and extensively 
to utilise these butterflies as food, notwithstanding 
their excessive abundance everywhere, and the exceed= 
ing ease of their capture, was the Brewer blackbird 
(an omnivorous bird which habitually eats whatever 
is most easily available, from flies and stinkbugs to 
seedling grain and fruit), which, in common with the 
farmyard chickens and ducks, took them in great 
quantities. Even this rather moderate attack upon 
butterflies by North American birds (under conditions 
so exceptionally favourable) far surpasses the aggre- 
gate of all previous records. 
That North American birds very rarely molest adult 
butterflies is indicated by at least two lines of evidence. 
In the first place, observers seldom or never see a butter- 
fly pursued or eaten by a bird. One cannot ordinarily 
by field observation distinguish the insects taken by 
birds, because the majority of them are inconspicuous 
forms. But if butterflies were taken, even uncom- 
monly, field naturalists should be able to note the 
fact more often than once or twice in a lifetime. It 
is a noteworthy fact to American observers how very 
seldom, if ever, they see a butterfly taken by a bird. 
For a number of years trained experts of the United 
States Department of Agriculture have been engaged 
in determining the food of native birds by examina- 
tion of the contents of thousands of bird stomachs 
