Frederick William Levander.

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having a Dawes eye-piece, he made a hole in a card diaphragm
with a red-hot needle, and then saw the dark body of the planet
distinctly against the light of the sky, but the circle was not
quite complete.

Obser'vations of the Zodiacal Light : by Capt. Noble.

On March 3, 1870, the zodiacal light was brighter than the
author had ever seen it before, surpassing the brightest part of
the Milky Way in Cassiopeia and Cygnus, which was visible near
it. The cone of light included the stars a, /3, and y Arietis, but
not the Pleiades, which were separated from it by a clearly-
marked piece of sky. Notwithstanding books lay down that the
light follows the course of the ecliptic, or very nearly so, on the
present occasion it departed widely from that direction to an
extent which was. estimated at 20^ at least.

On Further Changes in the Coloured Belt of Jupiter : by Mr.
Browning.

The author exhibited a large drawing of Jupiter, with the
colouring to which he had drawn attention. It had lately under-
gone much change, the coloured part being only the northern
half of the equatorial belt, so that it was more correct to say
there were two belts — the southern a pure white, the other
yellow but more dim than before. This white belt was the only
part quite free from colour. His last drawing was on January
30, 1870, at ph. 36m., but the planet was then very low. The
dark belts were imperfectly formed and not well defined. The
colouring again covered the whole of the equatorial belt, and
there were other changes. The colour over all the equatorial
belt was tawny yellow. South of this was a very dark band,
and a narrower one on the north. Above each of these was a
narrow bright white belt. The outbreak of colour, therefore,
appears to be on the increase. The planet should be careftilly
observed by all astronomers having a westerly look-out, and
with the Astronomer-Royars new eye-piece to counteract the
low elevation.



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'JZ Meeting of the Royal Astronomical

The President was astoiusbed at the great breadth of the equa-
torial belt as shown in Mr. Browning's drawings. It was half as
broad again as generally seen.

Capt. Noble asked whether the festoons along one margin of
this belt, formerly visiblfe, had disappeared.

Mr. Browning could not say. He did not see them then, and
always drew exactly what he saw only.

Mr. Stone mentioned a curious effect of different powers in
observing an eclipse of Jupiter's third satellite last Sunday week.
He was using a power of ooo, and was struck by the great faint-
ness of the planet, and put on a lower one to view it well. He
then again used the high power to observe the eclipse, which he
witnessed, and returning to the low power, found the satellite still
visible, and saw it again put out.

On the Corona visible in Solar Eclipses', by Mr. Proctor.

In this paper the author dwells on some of the important cha-
racteristics of the corona, which show that it cannot possibly be
a terrestrial phenomenon, a view which has lately been somewhat
advocated. The first argument in favour of the conclusion that
the corona cannot be connected with our atmosphere is derived from
the feet that the moon appears as a perfectly black disc in the sky,
showing that the light forming the corona is behind it, whereas, on
the other theory, had it been due to our atmosphere there would
have been a glare of light in front, which would more or less
have illuminated the body of the moon. Mr. Proctor illustrated
his arguments further by means of a diagram of the moon's
shadow falling on the earth and its atmosphere, which he explained,
and said that if we applied the test of observation to this rea-
soning it would be found correct. The prominences and chromo-
sphere might illuminate the edge of the disc, but if the glare were
in our atmosphere it would affect it all over. In an annular
eclipse the observer ought to see a black disc with light all round
lasting only the few seconds of annularity, and it will be found that
this has been noticed. In a total eclipse the edge of the moon
should be found somewhat brighter, and Mr. Baily has recorded
such an observation. If the corona of a solar eclipse be terres-
trial, it ought to be seen in partial eclipses, and before and afler
totality. Capt. Noble's paper to-night shows that there must be
a light background beyond Venus for the planet to be seen as a
dark body. What is the corona, if it be not in our atmosphere ?
It has been suggested that it is the thick richer part of the zodia-
cal light. The author inclined to this view, and was sorry to
hear Capt. Noble's observation that the light was not in the line
of the ecliptic, but it certainly, as a rule, follows that direction,
and especially where it is best seen. There may be reasons for
supposing that this is a ring at some distance from the sim, but



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Society i March ii, 1870. 73

the appeai-ance is not accordant ^ith Mr. Balfour Stewart^s elec-
trical theory. Were this correct, it would not rise and set. We
have looked too much at the physical characters and neglected the
mathematical objections. It would change position with the
latitude. In fact it cannot be near the earth, and must be at
least as far as the moon. In the tropics the zodiacal light increases
in brightness as it approaches the sim's place, and if we could
trace it up to the sun, it would be at least as bright as the corona.
Le Verrier's ring of bodies within the orbit of Mercury would
account for some of its perturbations. Mr. Baxendell thinks
meteoric phenomena and weather changes require some such
view. As long as the meteors were supposed to be a ring at
about the earth's distance there was no difficulty, but now we know
their orbits are very eccentric. There are 56 systems of them,
and they must be millions of millions in number, and it may be
possible that some may yet be seen during eclipses. The paper
concluded with suggestions for observations at the next total
solar eclipse, in order to ascertain what the corona really is, and
also proposed the appointment of a committee to consider the
course to be taken on that occasion.

Capt. Noble : My paper was not written to support any theory
whatever, but to state that, while the books tell us the zodiacal
light follows the course of the ecliptic, on this occasion it formed
an angle of 20° with that line.

The President : At Malta the light is seen the same as here,
but brighter. It is two or three times as light as the brightest
part of the Milky Way, and at once fixes the attention. It is
visible" in spring and autumn, but best in Februaiy. I cannot
say I have noticed a positive shadow cast by it, but it is very
bright. It gives a perceptible light to the earth, and generally
follows the path of the sun. It includes Aries and the Pleiades,
and sets with them.

Capt. Noble : On the night of my observation it was noticeably
brighter than the Milky Way in Cygnus.

Mr. Proctor : According to my idea, that it is the richer part
of the meteor system in the neighbourhood of the sun, and pro-
bably extending as far as Mars, it need not be consistently bright.
I have dealt with the spectroscope observations of the corona,
which are not exact enough at present. The meteors ought to be
incandescent, so that there would be reflected light and incan-
descence, giving a mixed spectrum — ^a continuous one, and bright
lines. Its polarisation would also have to be examined.

Mr. Lassell : I don't think the zodiacal light has ever been seen
at a total eclipse.

Mr. Proctor : Probably, if the observer would keep his eyes in
darkness for some time previously, he might see it.



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74 Meeting of the Royal Astronomical Society.

Dr. Mann enquired whether the President, when observing at
Malta, had noticed the suddenness with which the light loomed
up ? He had seen this happen twenty times in the tropics.

The President: Malta is 35® North. I have not noticed the
fact ; but in the tropics the light is much stronger.

Mr. Browning handed round a recent drawing of Venus, and
stated that, without any special contrivance, he could see the
globe of the planet.

Capt. Noble pointed out the difference in aperture between his
4' 2 -inch Achromatic and Mr. Browning's 12 -inch reflector.

Mr. Chambers enquired whether the Government proposed to
assist astronomers in going out to Spain to observe the eclipse of
December next ?

The President : The Government does not propose to do any-
thing of the kind ; but the Council is preparing to lay before them
a statement of the required observations, and to urge the neces-
sity of some assistance.

Mr. Stone : If gentlemen be sent to observe polarisation, I hope
there will be three at least, as two might contradict one another.
The recent accounts from America make this a most puzzling
question. In India, all agreed the corona was polarised in a
plane passing through the centre of the sun ; but the American
observers say it has nothing to do with the centre of the sun. I
hope this will be made a special subject of study. Several parts
of the corora ought to be examined. Perhaps in India they did
not go entirely round. A sufficient part of the corona should be
tested, so as to be sure the plane passes through the centre of the
sun.

A Gentleman enquired whether any connection had been
established between the zodiacal light and the retardation of
Encke's Comet ?

Mr. Stone : It has been suggested, but not established.

The meeting then adjourned.



Paris Observatory. — M. Delaunay has been appointed
Director of the Paris Observatory in place of M. Le Verrier^ and not
M. Faye, as at first reported.



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( 75 )



COBRESPONBEKCE.



N.B. — We do not hold ourselves answerable for any opinions
expressed by our correspondents.

TO THE EDITOR OF THE ASTRONOMICAL REGISTER.



ly ARRESTS COMET.



Sir, — ^The following ephemeris of this body for the month of April will
be useful to some of your readers : —

Berlin Mean Moon.



R.A.






N.P.D.


1870. h. m.


s.







/


April f ... 16 13


12




88


I


3 ... 16 13


59




87


39


5 ... 16 14


40




«7


17


7 ... 16 15


«5




86


54


9 ... 16 15


44




86


30


II ... 16 16


7




86


5


13 ... 16 16


13




85




15 ... 16 16


32




85


16


17 - ... 16 16


35




84


50


19 ... 16 16


3>




84


a4


21 ... 16 16


20




«3


5'


23 ... 16 16


2




83


31


25 ... 16 15


36




83


5


27 ... 16 15


3




81


3^


29 ... 16 14


^3




82


12


I remain, your


obedient servant,


Windyhills Observatory, Bickley :




G.


F. CHAMBERS.


March 7, 1870.










REFLECTING


TELESCOPES.





Sir, — ^I shall feel grateful for some really reliable information upon the
following point : —

Does the separating power of a telescope depend upon its aperture only ?
or upon its aperture and focal length combined ?

In order to reduce the matter to its simplest form, I will confine my
question to Newtonian reflectors of perfect parabolic curvature and perfectly
mounted. Starting with a lo-in. mirror, 7 ft. 6 in. focus, I suppose that
in separating power this would be surpassed by a 12-in. mirror of the same
focal length, and also by a 12-in. mirror of the same proportionate focal
length, 9 ft. Now, taking a series of 12-in. mirrors, whose focal lengths
gradually increase from 9 fb. to 20 ft., will all of these be superior in sepa-
rating power to the lo-in. mentioned above? Or, if not, at what stag© in
the series will the superiority of the larger aperture be neutralised by
the greater proportionate focal length ?

I remain, Sir, faithfully yours,

Aberdeen, March 1870. ARTHUR W. BLAOKLOCB:.



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y6 Correspondence.

SPECTBOSCOPE CONSTRUCTION.



Sir,— May I enquire, througli the pages of the Begtster^ whether one of
your numerous array of talented correspondents would kindly contribute an
article on '* Spectroscope Construction " ? I mean an article containing a
few practical directions such as would enable an amateur like myself, by
the purchase of suitable prisms, and the exercise of a little ingenuity, to
construct a simple spectroscope suitable for a telescope of, say, from two to
three inches aperture.

In a well-known weekly journal, which devotes some space to practical
astronomy, I hare noticed that this question has been asked very frequently
without eliciting any reply ; therefore I think that such a subject as is now
enquired for would possess some general interest.

I am, Sir, yours truly,

Dalston, March lo, 1870. W. P.



TELESCOPE PERFORMANCE,



Sir, — ^As many of your correspondents take an interest in comparing the
performance of their telescopes with others of a similar aperture, and as I
believe there are many of the same aperture as my own, viz. 4^ inches,
spread throughout the country, and by various excellent makers, I send you
a list of a few test objects well seen during the last two or three months.

€ Arietis clearly divided with a moderate power, ri Orionis divided with
high powers ; a very slight appearance of flattening of the disc of the smaller
and dull-coloured star with a power of 350. This star appears the utmost
limit of the dividing power of my instrument. I have a Huyghenian eye-
piece by Dallmeyer, which gives a power of at least 520 or 530, and with
this power star discs are beautifully defined in good air. This 0. g. will
also elongate, although only slightly, 7^ Andromedse and C Cancri. As to
tests of illuminating power, on four or five occasions I have seen, during the
last two months, the 6th star in the Trapezium, once beautifully steely,
best power 225. The fifth is generally visible. The faint companion of
A Orionis I see steadily with all powers, more difficult with the lower ones.
1 5 Monocerotis I see quadruple. On three or four occasions I have seen
steadily the 15th mag. star companion of the double 52 Arietis at 5" — ^best
power 1 50 ; this small star is a beautiful test object. All these objects
have been seen steadily, not as glimpse stars, but by direct vision. 1 see
1 5 stars in the group Orionis, that is to say, if the apparently uppermost
or really southern star <r is considered as one of the group. One or two of
these, although really seen, are only to be brought out by averted vision
and high powers. The little nth mag. star, in this group, is not put out,
as it were, with 450 ; and I have also seen the companion of a Lyrae with
a very high power. I have seen six spots on the floor of Plato, and I dare-
say I could make out more under very favourable circumstances, Jupiter
will not often stand a power higher than 225 ; the outline of the disc is
sharp with 500 ; but there is not sufficient illuminating power to bring out
the belts with a high power. Venus, on the contrary, will bear a consider-
able amount of magnifying power, if at a good altitude, and in a moderately
dark sky. I have seen this planet, lately, really well defined with an
achromatic eye-piece, magnifying on my telescope nearly 500 times. I like
the performance of these microscopic eye-pieces on planets, even with the
refractor, better than any others. I have been used to much larger aper-



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Correspondence. Tj

tures, both reflectors and refractors, but for its small size this is the best
instrument I ever saw. The glass is the manufacture of Messrs. Chance of
Birmingham, and is evidently of the finest quality, without which, however
perfect may be the skill of the optician, the result of his labour can never
be satisfactory. I have had an opportunity of testing the dividing powers
of a good many instruments, both reflectors and refractors, and as far as my
experience goes, dividing power of telescopes does not depend alone on
aperture, irrespective of focal length and of figure.

I am, Sir, yours truly,
Yarmouth: March 1870. . W. MATTHEWS.



THE HACKKEY SCIENTIFIC ASSOCIATION.



Sir, — ^You will be pleased to learn that the " Hackney Scientific Associa-
tion," whose opening conversazione you very kindly noticed a few months
back, is progressing very satisfactorily. The number of members (although
still small) is nearly twice as many as in the previous session ; while the
papers read have been of considerable interest and importance, a great
proportion of the subjects having been astronomical

The titles of those read already are as follows : —

I. Comparative psychology.

a. The nebular hypothesis of La Place in the light of modem discovery.

3. The local origin of disturbances affecting the Earth's surface.

4. The markings on the planet Jupiter.

5. Tyndall*s cometary theory.

6. The planetary origin of weather changes, with the probable weather
for 1870.

7. Kecent researches into organic dust.

Beports of these (often very full) appear in the various local journals, and
thus contribute, we hope, to the spread of scientific knowledge.

No. 4 appeared in fuU in The Mechanic for Feb. 5, 1870, and I take the
liberty of enclosing a local report of No. 6, which, bearing upon the weather,
may possess some interest to astronomers. Of course the report does not
give Mr. Pratt's method of calculation, but past experience assures us of
the correctness of his results.

We are endeavouring to form a small Library of scientific works for the
use of members ; for without a library we find it difficult to obtain any
large acquisition of members, and being without &ny funds to speak of, we
find the task progresses very slowly. If any of your numerous readers had
any old books, upon astronomy or other sciences, to spare, we should
receive them gladly.

Perhaps you would kindly mention this latter fact in the comer of the
Segister,

I remain, yours truly,

Meeting Kooms : H. W. EMONS,

26 Fleming Street, Kingsland Boad. Hon, Sec,



THE SUPPOSED PLANET VULCAN.



Sir, — Another systematic series of observations of the sun are about to
be commenced, with the object of re-discovering the suspected new planet
Vulcan in transit. There will be about twenty-five gentlemen engaged in
the affiiir, each of whom has a certain fixed time every day during which to



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78 Correspondence.

carefully examine the solar disc. The obserrations inll extend over the
period from March 20 to April 10, and there is every reason to suppose
that the search will end satisfactorily, if not successfully. The fact of the
time of maximum frequency of the solar spots having arrived will give
additional interest to the observations. The list of those engaged in the
search includes the names of Messrs. W. B. Birt, F.E.A.S. ; G-. J. Walker ;
T. G. E. Elger; E. B. Knobel; J. Birmingham; T. P. Barkas; James
Cook; Henry Pratt; Jno. Watson, F.E.A.S. ; T. W. Backhouse; H. W.
HoUis, F.R.A.S. ; T. Wilson ; P. Vallance ; A. P. Holden ; H. Ormesher ;
and others.

When the observations have terminated, I will send you a particular
account of the results obtained.

I am, dear Sir, truly yours,

Bristol: March 1870. WILLIAM F. DENNING, Hon. Sec. O.A.S.



NOTES ON THE WONDERS AND BEAUTIES OF THE
STARRY HEAVENS.



Sir, — I regret to see that the numerous contractions in my MSS. of ob-
servations on Cassiopeia have been a source of difficulty, and the cause of
several errors. The sole object of the abbreviations was the fear of extend-
ing what was already a rather lengthy article. I therefore take the present
opportunity to correct, and at the same time to add a few notes as a post-
script to my paper.

(c). The colour of this star is greenish, not Greenwich, as printed. The
last clause of this paragraph should read, — J° north of this is 52, a creamy
star, with a faint distant companion south following. ^^ preceding this is
a little cluster, containing two open pairs.

The noticesof n and < are printed together, instead of being in two separate
paragraphs as intended. After saying of tj, — " I find the colours distinct,
yellowish and purple, a fine pair with 220 " — ^the notice of this stM is con-
cluded. Then should follow, as a separate paragraph, the notice of », or
P. II. 72 ; meaning, of course, star No. 72, in the second hour of right
ascension of Piazzi's catalogue.

(ic). I may be allowed to call attention here to the singular arrangement
of the stars adjacent to this object, as well worthy of further consideration.
It can scarcely be supposed that two sets of three nearly equal stars should
be so located in space that their lines of direction should lie nearly at right
angles to each other, and at the same time should intersect at this star,
simply as the result of accident. Moreover, this is not a solitary case ;
there are numerous instances of singular proximity and curious arrange-
ment among the stellar host which the researches of miodem astronomers
have shown to be the result of real physical connection ; and we have good
reason for believing that such connections exist in the sidereal heavens in a
much greater number of instances than is generally supposed.

(A). Under the notice of this star, the position of a wide pair of stars of
8, 9 magnitude is given as 300" instead of 300°.

I take the present opportunity of informing my kind correspondents that,
since completing these observations, circumstances have occurred which
have rendered it desirable that I should remove to London. I beg, there-
fore, to append my address, and shall be happy to receive any communica«
tions relating to observational astronomy.

I Braywici Cottages, I am, Sir, truly yours,

Prescott Place, Clapham. C. GROVER.



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Correspondence. 79

THE MOON'S MOTION.



Sir, — In the supplementary number of the Astronomical Register of 1S69,
I observe a letter from Mr. Elvins on the motion and physical constitu-
tion of the moon. Mr. Elvins certainly deserves the thanks of all who,
like himself, deny the axial rotation of the moon, inasmuch as he has had
the courage to propound a theory to account for the phenomena of libration,
which fatal objection to their theory has always hitherto been prudently
Ignored by the non-rotattonists in the many letters which from time to time
have appeared on this subject in the pages of the Register^ although they have
been frequently challenged on this point.

Mr. Elvins teUs us that he was formerly a believer in the moon's rota-
tion, but that he has since changed his opinion — ^he does not say by what
argument he was convinced — but that which he has made use of in his
letter, in order to convince others, is assuredly an erroneous one, since it
rests upon an undue assuniption ; and exactly the same may be said of the
illustration relied on by Mr. Perigal in the Register of March x 869, of
which Mr. Elvins so highly approves. Both these gentlemen forget that
the moon is not rigidly connected with the earth by a bar of iron or any
material bond, but by a force, invisible and intangible, which, according to
universal consent, is simply defined as " varying directly as the mass
attracted, and inversely as the square of the distance of the latter from the
centre of force." If to this Mr. Elvins adds that it possesses likewise the
singular property of causing the body attracted to keep always the same
face turned towards the centre of attraction, he is seriously tampering with
the law of gravitation, which with this addition becomes quite another
thing from that discoveied by Newton ; and, in that case, the whole of modem
astronomy would need to be recast.

Astronomical innovators, I fear, are rather apt to indulge some favourite
theory on very slight grounds, and without due regard to its consequences
or agreement with facts. Let Mr. Elvins ascertain by direct experiment
whether, when one body revolves /r^y around another, i.e. not rigidly con-
nected with it, under the influence of gravity, it does, or does not, turn
always the same face towards the attracting centre. This may easily be
tried, and would set this part of the dispute at rest for ever. Let me refer
him to a letter, signed "P." on page 170 of vol. ii. of the Register: which
letter up to the present time has not been answered.

Mr. Elvins, moreover, has based his theory of libration upon the assump-
tion of facts which do not exist. What is cieJled libration is not an adwal
motion of the moon, but an apparent motion^ to be accounted for simply and
readily on the received theory of astronomers, that the moon's rotation is
equable in speed while its revolution is variable ; but not to be accounted



Online LibraryFrederick William LevanderThe Astronomical register: → online text (page 10 of 36)