Fune 1, 1871 | 
NATURE 
85 

at Rio Janeiro were coincident with polar lights in the northern 
hemisphere. At all events I believe that the attention of men of 
science is not sufficiently directed to this coincidence of northern 
and southern polar lights, at least not as much as it deserves in 
respect to the theory of polar lights at all; and I should be very 
glad if, in consequence of this notice, authorities would discuss 
this highly interesting phenomenon in NATURE. 
I shall later, according to my diary, accurately describe the 
display of this splendid aurora australis, and mention the influ- 
ence which it perhaps or probably had on the abnormal meteoro- 
logical phenomena, which I observed during the succeeding days. 
ApOLF BERNHARD MEYER 
Manado (Celebes), January 9 
P.S.—I beg to contribute to the records in NATURE of earth- 
quakes, &c., over the whole globe :— 
November 20, 1870, afternoon, an at first vertical, then hori- 
zontal, rather heavy shock at Manado. 
January 28, 1871, 4h., a slight, very local shock in a part of 
Manado, 
Manado (Celebes), March 5 
The Eclipse Photographs 
As an ardent and not inexperienced votary of photography, I 
am fully alive to the value of photographic evidence, and regard 
with enthusiasm each fresh victory which photography achieves, 
yet I cannot myself look with any very great degree of satisfac- 
tion upon the photographs of the late solar eclipse either as 
examples of photography or as evidence contributing to our 
knowledge of solar physics. In saying this I make no reflection 
whatever upon the ability or efforts of those by whom the pictures 
were produced. On the contrary, I am aware that when these 
pictures were taken the first grand requisite of photographic suc- 
cess—a clear view of the object to be represented—was scarcely 
to be obtained. Briefly ; from a technical point of view, the 
pictures are of but indifferent definition, and the identity of the 
coronal rifts in the Cadiz and Syracuse photographs not satisfac- 
torily conclusive, in addition to which in the picture by the 
American observers, the so-called coronal light extends a long 
way over the lunar disc, which seems to me to preclude the 
possibility of its being other than a phenomenon of terrestrial 
meteorology. A few weeks ago, when the sky appeared almost 
cloudless, I observed a beautiful lunar halo, very much resem- 
bling the so-called corona, which I apprehend no one would 
attribute to anything but atmospheric moisture. Why, then, in 
the instance of a sky burdened with innumerable clouds, should we 
attribute the halo of light surrounding the solar disc to other than 
atmospheric causes, even though there should be something which 
might be mistaken for a coincidence in two distinct photographs 
oer or other of the rifts which were characteristic of that 
alo? 
Manchester, May 26 D. WINSTANLEY 

Eozodon Canadense 
PERMIT me to state that the presumed ‘‘ important bearing ” 
on the so-called ‘‘Eozéon Canadense,” of the principal fact 
noticed in the communication entitled Palceozoic Crinoids, 
which appears in NATURE of May 25th, is discussed in a 
paper by Dr. Rowney and myself, contained in the forth- 
coming number of the Proceedings of the Royal Irish Academy, 
now on the eve of publication. The paper referred to is a 
reply to the articles by Drs. Dawson and Sterry Hunt, which 
appeared in the last (second) number of the Proceedings. 
Glenoir, near Galway, May 29 WILLIAM KING 
WITHOUT going into the vexed question as to whether Eoz6on 
Canadense is or is not of organic origin, I may be permitted to 
express some surprise at the new, and, to say the least of it, 
startling theory broached by Mr. Perry in last week’s NATURE, 
of the vaporous formation of a certain limestone. The only facts 
brought forward in support of this view are, its occupying 
pockets, its foliations, and its conformation with irregularities of 
surface in the pre-existing rock. All these could be as well ac- 
counted for on the supposition of deposition from aqueous solu- 
tion, without doing violence to the fact that carbonate of lime is 
not volatile at any temperature. 135 ahs Sl 

THE INEQUALITIES OF THE MOON'S 
MOTION 
HE following is an abstract of the method of com- 
puting the inequalities in the motion of the moon 
which are due to the action of the planets, proposed by 
Prof. Newcomb in the paper presented to the Academy 
of Sciences of Paris on April 3. 
When we consider the movements of the sun, moon, 
and earth, under the sole influence of their mutual attrac- 
tion, the position of each of these three bodies in space 
will be given in terms of eighteen arbitrary constants, and 
of the time. The problems of the relative movement of 
the moon around the earth, and of the movement of the 
centre of gravity of the earth and moon around the sun, 
have been solved with a degree of approximation sufficient 
at least for the purposes of astronomy. Thus, we have 
the co-ordinates of any two bodies relatively to a third, or 
relatively to the centre of gravity of the system, in terms 
of twelve elements and of the time. It only remains to 
add the expressions for the uniform movement of the 
centre of gravity ina straight line, to have the general 
expressions for the co-ordinates of each body. 
We have then only to consider the action of the planet 
to vary the eighteen elements according to the method of 
Lagrange, to have the movements of each of the three 
bodies under the influence of the attraction of the planet. 
Unfortunately, the expressions thus obtained are at first 
extremely complicated. We have to computea coefficient 
corresponding to each combination of the elements taken 
two and two. The entire number of the coefficients is, 
< 18 
Nigh BS 48 = 153 
2 
tains eighteen products of the partial differential cveffi- 
cients of the co-ordinates of the three bodies relatively to 
the elements. These latter differential coefficients are so 
complex that the formation of any one product would be 
a considerable labour. The direct formation of the co- 
efficients required is therefore impossible. The paper in 
question is principally devoted to an explanation of the 
simplifications which may be introduced into the problem. 
It is first shown that all the coefficients formed by com- 
bining any one of thesix elements which fix the position 
of the centre of gravity with any of the twelve elements 
of the relative motion, vanish identically, while the com- 
binations of those six elements with each other give only 
the principle of the conservation of the centre of gravity. 
This leaves only sixty-six combinations. It is then shown 
that, ifthe elements are divided into two classes, the first 
class being the mean longitudes, the longitudes of the 
perigees, and the longitudes of the nodes of the sun and 
moon, and the second the mean distances, eccentricities, 
and inclinations, the coefficients vanish whenever the two 
elements combined belong to the same class. The number 
of coefficients is thus reduced to thirty-six, and they are 
simply the differential coefficients of six functions of the 
elements of the second class. These functions are formed 
an extremely simple process when we have the rect- 
angular co-ordinates expressed as functions of the elements 
and the time. 
The remainder of the process is simply one of the 
development of a very complex perturbative function, and 
is of no especial interest. 
therefore, And each coefficient con- 

THE HELIOTYPE PROCESS 
sae one of the recent sozrées of the Royal Society given 
by General Sabine at Burlington House, Messrs. 
Edwards and Kidd exhibited at work the new heliotype 
process, whereby photographic pictures can be very 
rapidly copied in by the aid of the printing-press. The pro- 
cess is very inexpensive, and so rapid that if one of the 
pages of NATURE were sent to the works, it could be 
