Zor 
578 
NATURE 
[April 20, 1 882 
inches face, of 60°, and the spectrum will be brought to a 
focus on a sensitive plate by a lens of a mean focus of 9 
inches. An attempt will be made to secure the whole 
of the spectrum, and for this purpose the plate requires 
to be inclined at an angle of 40° to the axis of the lens. 
The spectrum which it is hoped to obtain by this arrange- 
ment would have required an hour’s exposure some years 
ago. 
With this instrument attempts will be made to secure a 
photograph of the flash of bright lines at the beginning 
of totality, and the spectrum of the corona during totality, 
an arrangement being made for a comparison solar spec- 
trum after totality by shutting off half of the slit. 
So much, then, for the work suggested by applying 
views and methods which have been broached since the 
last eclipse. 
The remarkable form of the corona, and its still more 
remarkable extension in 1878, and its great variation 
from that seen in prior eclipses with a single exception— 
that of 1867—will render observations of the form and 
extent of the corona in the present year of the highest 
importance, even if we had not Dr. Siemens’ suggestive 
hypothesis to lend a more than usual interest to it. 
I give an illustration (Fig. 1) copied from the American 
volume, which I owe to the courtesy of the Superinten- 
dent of the Naval Observatory at Washington, to show 
how my own observations of that eclipse, an account of 
which was sent to NATURE from America at the time, 
have been borne out by a discussion of the photographs. 
Side by side with it, in order that the equatcrial extension 
and the almost identical tracery at the poles can be seen, 
I give a copy of a drawing made in 1867, both sets of 
observations having been made four years before the sun- 
pot maximum (Fig. 2). 
Here, indeed, we have food for thought; for the cur- 
rents in the solar atmosphere, revealed by these drawings, 
seem to be exactly those demanded by Dr. Siemens; 
and indeed, his hypothetical diagram which appeared in 
NATURE a few weeks ago, should be compared with them, 
in order that the points of resemblance may be grasped. 
With reference to the other drawing (Fig. 3), which 
shows the remarkable observation made by Prof. New- 
comb, I cannot do better than make the following 
quotation from the volume in question :— 
“Tt had always seemed to me that the visual study of 
the faint outlying portions of the corona would necessarily 
be interfered with by the brilliant interior portions unless 
the view of the latter were intercepted. I therefore made 
preparations to repeat the experiment unsuccessfully 
attempted at Desmoines in 1869, of hiding the central 
corona by a screen about 1° in diameter, and examining 
such portions as might be visible outside of it. The 
screen now used was made of wood, about 12 inches in | 
diameter, and was mounted on top of a telegraph pole 
which was set on the elevated ground to the west. The 
altitude and azimuth of the sun at the moment of central 
eclipse were carefully calculated, and the screen fixed in | 
such a position that when viewed from the top of a stake 
driven in the ground alongside of my telescope it would 
cover the eclipsed sun. The angular diameter of the 
screen as measured with a sextant from the stake was 
577, its distance was about 60 feet. As this would cut off 
about 12’ of the corona all round the moon I considered 
it ample for the purpose, but the results showed that it 
might well have been somewhat larger. 
“JT remained in the dark room until about three minutes 
before the commencement of totality with the view of 
having my eyes as sensitive as possible. I then walked 
to the telescope, keeping my eyes partially protected from 
the light. The lurid colour of the landscape was very 
striking. The light seemed no longer to be that of the 
sun but rather to partake of the character of an artificial © 
illumination. This appearance is very readily explicable 
by the fact that the light coming only from the limb of 
the sun belongs principally to the red end of the spectrum. 
As the last ray of sunlight was disappearing I stepped to 
a stake driven into the ground, the top of which marked — 
the point from which the sun would be entirely hidden by 
the screen. A bright corona was plainly visible all round 
the screen, although a portion 12’ from the limb of the 
sun was entirely cut off. My attention was immediately 
attracted by a faint blush of light, extending out on each 
side at an angle of about 45° with the horizon, each end 
terminating in a long narrow ray. I made a very careful 
estimate of the length of these rays as 6° from the disc. 
They shaded off by insensible gradations, and struck me 
as having a great resemblance to a representation of the 
zodiacal light on a reduced scale. They were to all 
appearances continuous with the corona. With a view 
of judging whether their direction coincided with that of 
the ecliptic, I tried to judge whether the western one 
pointed towards the planet Venus, then plainly visible 
near the horizon. Its direction was apparently very 
slightly below that of the planet. 
“ The outlying portions of the corona other than those 
rays were extremely irregular; that is, there were several 
rays and other irregularities extending out in different 
directions. As these were common phenomena, I took 
no note of their details.” J. NoRMAN LOCKYER 
April 18 
(To be continued.) 
PROF. WIESNER ON “THE POWER OF 
MOVEMENT IN PLANTS” 
Das Bewegungsvermogen der Pflanzen: eine kritische 
Studie tiber das gleichnamige Werk, von Charles 
Darwin, nebst neuen Untersuchungen. Von Julius 
Wiesner. 8vo, pp. 212. Three Woodcuts. (Wien: 
Holder, 1881.) 
peer. attempting to reply to some of Prof. Wies- 
ner’s criticism, it is a pleasure to record my appre- 
ciation of the courteous spirit in which his book is written, 
and the uniformly respectful tone which he employs 
towards my father. His criticism is so extensive that 
there is hardly a single point of any importance in “‘ The 
Power of Movement in Plants” with which Prof. Wiesner 
agrees. Yet in spite of this far-reaching difference of 
opinion, he is good enough to express himself warmly as 
to the value which the book possesses. 
Wiesner devotes a good many pages to Circumnuta- 
tion, and as this phenomenon and the theories connected 
with it form an important part of ‘‘ The Power of Move- 
ment in Plants,” I shall begin with this question. In the 
first place Wiesner finds fault with one of the methods 
employed by us in our observations on circumnutation, 
and gives a diagram (Fig. 3, p. 161) which shows that 
the method may lead to false conclusions. In the method 
of observation criticised by Wiesner, the position of the 
plant at any moment was determined by making a dot on 
a glass plate in such position that it was in a line with a 
mark on the organ whose movements were to be observed 
and with a stationary mark behind or below it. This 
method is obviously open to objections, and we never ima- 
