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Young, C. A

Dartmouth College 
Dartmouth Digital Commons 
Dartmouth Scholarship Faculty Work 
1-1-1872 
Spectroscopic nomenclature 
C. A. Young 
Dartmouth College 
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Dartmouth Digital Commons Citation 
Young, C. A., "Spectroscopic nomenclature" (1872). Dartmouth Scholarship. 4073. 
https://digitalcommons.dartmouth.edu/facoa/4073 
This Letter to the Editor is brought to you for free and open access by the Faculty Work at Dartmouth Digital 
Commons. It has been accepted for inclusion in Dartmouth Scholarship by an authorized administrator of 
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© 1872 Nature Publishing Group
NATURE IOI 
acids; the passage from' one class of alcohols, &c,, to 
another ; and very many other· points of great scientific 
val11e, too commonly overlooked in ·the text-books, are 
here all carefully noted. As we s.aid, the book requires 
attentive Hudy, but this it will certainly repay. 
M.M.P.M. 
Thermal Paths to the Pole. An Address delivered-before 
the St. Louis Mercantile ~ibrary Association in January 
1872. By Silas Bent. 
IN this pamphlet the author repeats the substance of a 
lecture delivered in 1868, the object of which was to show 
that the continuations of the warm Gulf Stream of the 
Atlantic, and of the Japan current in the Pacific, afford 
the only. practicable avenues by which ships can enter an 
assumed open sea round the North Pole; and points out 
how the more recent Arctic explorations have confirmed 
the views then advanced. 
The author's opinions should derive weight from the 
fact that he was one of the leading scientific observers in 
the American expedition of 1852, during which the Japan 
current was mapped out, and from his twenty-five years 
vf observations at sea. 
. So far as the warm drift continuing the Gulf Stream 
into the Arctic region between Spitzbergen and Nova 
Zemlia is concerned, the theory ot its intluence (which, 
however, can hardly be called "original/' since it has 
Leen current among Arctic aulhoritie, for many years) 
has indeed been remarkably confirmed in the past year by 
Payer and Weyprecht's voyage in open water to 79° N. lat. 
But it remains to be shown that the summer current from 
the Pacific through the narrow and shallow pass1ge of 
B~hring Straits has any considerable influence on the 
condition of the Arctic basin. In the circumpolar chart 
which accompanies the pamphlet, Behring Straits has 
been carefully widened to admit the Kuro-Siwo in a bread1h 
quite equivalent to that of the Gulf Stream drfft. 
A considerable portion of the address is devoted to the 
description of a method by which "were it not for the in-
humanity of exercising such a power," the whole of Europe 
might be placed at the mercy of America. · Europe derives 
its mild climate from the Gulf Stream, and to divert this 
~tream from its present direction would be to make·• Europe 
a frozen wilderness." This grand result, the author believes, 
could be accomplished "by the possession of the Isthmus 
of Panama and the expenditure of half the cost of the 
recent war between France and Germany, in the excava-
tion of a sufficient width and depth of the rock only that 
intervenes between the Caribbean Sea and the Pacific.'' 
:V1r. Bent has himself, however, thrown some doubt on the 
entire practicability of his design by q11oting, in a previous 
paragraph, the belief expressed by Professor Maury that 
the great mass of the Gulf Stream is formed by that part 
of the equatorial current of the Atlantic which passes to 
northward of the Antilles, and which "must be a hundred-
fold greater than that which returns to the east from the 
Gulf of Mexico ;" he has also omitted to notice that the 
force of the drift in the Caribbean Sea is not directed 
in any degree against the narrower portion of the isthmus, 
and we presume that even Mr. Bent ,vould not attack 
the plateaus of Guatemala or Mexico. K. J. 
LETTERS TO THE EDITOR 
[ The Editor does not hold himself responsible for opinions expressed 
by his ccrrespondents. No notice is takm of anonymous 
communications.] 
Spectroscopic N omenclaiure 
Tiu: letter of Captain · Herschel upon "Spectroscopic No-. 
menchture,". which. appeared in NATURE of April 25 contains 
many criticisms that are eminently just and timely, but there are 
one or two p,;,ints in respect to which I should hke to express 
dissent, 
Thus as regards the name D 3 (to which he objects) for the 
yellow line of t~e c~romosphere spectrum, -it is not easy to see 
what othe~ des1gnat1on would better convey to. the mind an idea 
of its position iri the ~pectrum' and its importance, without in-
volv!ng ~ny assumption, or hypothesis even, as to the material 
causmg 1t. 
.To say nothing of the fact that the whole Greek alphabet 
~o_uld not suffice to !1ame one in three of the bright lines which 
have bee!1 observed m the chromosph~re spe;trum, there is this 
fo,ther difficulty, that if the letters are to be applied to lines in 
the order of discovery, "' is as likely to fall between " and /3 as 
anywhere else-, but if according to position in the spectrum, 1hen 
ev~ry discovery of new lines iiwolves a revision ·or the nomen- ' 
clat11re. · 
· it seems doubtful therefore whether any better system is pos-
sible than to designate lines by reference. to some standard map 
of the spectrum, as stars are catalogued by their right ascension 
and declination. 
An accurate chart of the solar spectrum on ~hich the lines 
should be mapped according to "inverse wave-length," proposed 
by Captain Herschel himself I believe, as well as by Mr. Stoney 
and. others, would sufficiently resemble the spectrum seen in a 
spectroscope to be equally convenient in the observatory with 
that of Kirchhoff, and would be free from the reproach of arbi-
trariness and irregularity in its scale. Such a chart would be 
most gladly welcomed by all spectroscopists, and would immedi-
ately supersede those of Kirchhoff and Angstrom. 
\Vith reference to the green corona line, he writes "and now · 
we have ' 1474.' No one knows what the true position of th1t 
line is. The line 1474 K is au iron line-, and it. is to the last 
degree improbable that the corona line is identical with it." I 
am not quite sure what is meant by the second clause. If only, 
that the position of this line may possibly (not by any means pro-
bably) be doubtful to the extent of ¼ of one of Kirchhoff's scale 
divisions, that is about ¾ the distance between the two E lines, I 
have nothing to object. . · · 
But if the sentence is intended, as one would naturally sup-
pose, to convey the idea that the position of the line is not very 
accurately determined, and may be considered uncertain to 1he 
· extent of several. scale divisions, it is certainly wrong. I know 
of what I affirm, and perhaps may be allowed. to refer to an 
article in this journal for Feb. 2, 1871, in which the evidence is 
st.i.ted as it was at that time, and it has received confirmation 
since. 
Indeed as this bright line is almost always visible in the chro, 
mosphere 10 an instrument of s1ifficient power, I think I may 
confidently appeal to Mr. Lock'yer or Dr. Huggins to bear me 
out in the statement that the bright scarlet line of the chromo-
sphere appears to coincide no more perfectly with the dark C, 
than does this green corona line with the dark line at 1474 K. 
I confess I am almost ·sorry that the spectrum ·of iron show~ a 
bright line coincident with 1474, for all things considered, I 
cannot think that iron vapour has anything to do with this line 
in the spectrum of the corona, and the coincidence has probably 
only served to mislead, 
But there are in the spectrum many cases of lines belonging to 
the spectra of different metals coinciding; if not absolutely, yet 
so closely that no existing spectroscope can separate them, and I 
am disposed to believe_ that this close coincidence is not acci-
dental, but probably points to some physical relationship, some 
similarity of molecular constitution perhaps, between the metals 
concerned. 
So in the case of the green coronal matter, is it not likely 
that, though not iron, it may turn out to bear some impor-· 
tant relation to that metal? And yet I for one should be 
very glad if the application of higher dispersive power should 
show_ ~he apparent coincidence to be merely a very close jux-
tapos1tion. C. A. YOUNG 
Dar~mouth College, U.S.A., May 16 
Historical Note on the Method of Least Squares 
THIS excellent method for the discussion of ·observations was 
published and first practically applied .by Gauss in his Theoria 
Matus, 1808. In the Amencan Journal of Science for June 
r87i;',·Mr. Cleveland Abbe has shown that Prof. Robert Adrairi, 
of New Brunswick, New Jersey, U.S., independently discovered 
the same method in 1808. I wish to call attention to what seems 
to me a singular oversight in the history of this subject, viz., to 


English

Spectroscopic nomenclature

Dartmouth College 
Dartmouth Digital Commons 
Dartmouth Scholarship Faculty Work 
1-1-1872 
The Sherman astronomical expedition 
C. A. Young 
Dartmouth College 
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Young, C. A., "The Sherman astronomical expedition" (1872). Dartmouth Scholarship. 4074. 
https://digitalcommons.dartmouth.edu/facoa/4074 
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© 1872 Nature Publishing Group
NATURE 
THE SHERMAN ASTRONOMICAL EX-
PEDITION 
BY the courtesy of Prof. Peirce, Superintendent of the 
U.S. Coast Survey, I am permitted to lay before 
the readers of NATURE, at the request of its editor, a 
brief account of the operations and results of the party 
which was stationed during the months of June, July, and 
August last at Shcrm1.n, the summit of the Union Pacific 
Railway. 
The expedition was organised under the auspices of the 
Co1.st Survey; the observations, other than those for 
determining the mere geographical and topographical 
constants of the station, being provided for from a special 
appropriation of 200,000 dols. granted by Congress, at 
the request of the Superintendent, and placed at his dis-
posal for the purpose of securing a series of astr0nomical 
and meteorological observations at some elevated point 
on or near the Pacific Railway. 
The party was under the charge of Gener:il R. D. 
FIG. I, 
Cutts, one of the most experien:ed officers of the Survey, 
and consisted of himself, A,sistaat Mosman, and Aid 
Colonna, with myself, my colleague Prof. C. F. Emer;;on, 
who wa, kind enough to act as my personala,sistant, and 
a young friend, Mr. C. K. 'Nead; we h1i als-:> a photo-
grapher, a mechanician, and a couple of serva,nts. A de-
tail of ab:mt a dozen of the most in~elligent s Jldi~rs fro_n 
Fort D. A. Russell at Cheyenne S!Uc!d as an es:ort, an:i 
15 . ?G '1'7 
\J u11 l I I I I I Ir 1 I I I 
l'j8 ?'11 
I Ii 11 I I 1 \ l I l I I I 1 I 
FIG. 2. -Spectrum of a Solar Spot, 
were 1nvaluable in keeping up the hourly series of meteo-
rological observations, and in many other ways, as well 
as in protecting us from any undesirable attentions of our 
red brethren ; not that the protection was ever actually 
needed, for we hardly saw· half a dozen Indians during 
the whole summer, except as p1.ssengers upon the rail-
way trains. 
The station was established in June, but it was not until 
July that I was able to join the p1.rty with Prof. Emerson 
and Mr. Wead. Our instrument had been forwarded by 
exp_ress, and was already on the ground. It was the 
Dar~mou~h College equatorial, bavin6 an aperture of 
9i40 m., with a focal length of 12 ft., provided with clock-
work and all the usual accessories, and fitted with an 
© 1872 Nature Publishing Group
108 NATURE LDec. 12, 1872 
automatic spectroscripe having the dispersive power of 
13 prisms. The instrument was loaned for the occasion 
by the trustees of the College, who, for the good of 
science, have never hesitated to send their most valuable 
apparatus to any portion of the earth ; and thus far, I 
am happy to say, have met with no loss in so doing. 
Our observatories, one for the transit instrument, one 
for the meteorological apparatus, and one for the equato-
rial, were "shanties" of rough boards, placed upon the 
summit of a slight elevation, some 150 yards S.E. of the 
railway station, and some 40 or 50ft. above the track. 
The altitude of the observatory was about 8,300 ft. above 
the sea ; the approximate latitude was 44° 7' ; the longi-
tude about 1h. 53·2m. west of Washington, or 7h. r4m. 
west of Greenwich. I give only approximations, the 
accurate reduction of the observations being not yet 
completed. 
To the east the horizon was bounded by hills of no 
great apparent e'evation, nor was there anything in the 
general aspect of the nearer landscape to remind the care-
less observer of his altitude. To the north, at a distance 
of about three miles, but seeming not more than half a 
mile away, rose some picturesque piles of granite several 
hundreds of feet in height ; to the north-west lay the so-
called Laramie hill, ; and from the north-west to the 
south, across the broad green Laramie plains, toward the 
mountains, many of them capped with perpetual sno 1v. 
In the south were Long's and Gray's peaks, some 60 miles 
away; nearly west lay somewhat nearer the great mass 
of Medicine Bow ; and between them, over the lower 
ridges, rose some of the high mountains of the Colorado 
parks. None of these snow-capped peaks have an eleva-
tion of less than 13,000 ft., and several exceed 14,000. 
Our principal object was to ascertain what advantage 
would accrue to astronomical, and especially to spectro-
scropic, work, by placing the instrument at a great eleva-
tion. Theory declares that the gain ought to be great, 
since it is certain that our atmosphere, by its contimnl 
current5, its i1npurities, 21~d its rc-fkctive pow-:r, is a most 
serious hi11dr,rnce to telescopic work, and at the height of 
8,000 fr.-more than a fourth of the who'.e is left below. 
The experiment of Prof. Piazzi Smyth, in 1856, on the 
Peak of Teneriffe, had already given a practical demon-
stration of the fact, so far as relates to ordinary tele,copic 
work; but that w.1, before the ,by of speCiroscopy. 
Although, on account of unfavourable weather, the 
amount of work accomplished was to some extent dimi-
nished, the results obtained were of considerable interest 
and value. 
In the first place, the geographical co-ordinates of the 
station were completely determined ; so that henceforth 
it will be a reference point and base for all the numerous 
surveys, geological and others, which are going on in 
that part of the country. 
Then a complete hourly meteorological record was 
obtained for nearly the whole of the months of June, July, 
and August, a record which, from the exceptional charac-
ter of the station, on the very back-bone of the continent, 
must possess the highest value, unless the fact that the 
season was also an exceptional one should prevent us from 
applying confidently to other years the conclusions it would 
indicate. 
If we may credit the residents of the country, especially 
an old trapper who had lived among the mountains for 
nearly twenty years, the amount of cloudy and rainy 
weather during the summer was most unusual. Deduct-
ing a single week, during which every night and the 
greater part of every day was fine, clear nights were very 
rare, and clear days only a little less so. Indeed during 
our whole stay there were but two afternoons during which 
work upon the sun could be kept up uninterruptedly from 
noon to sunset, though during the same time there were 
more than twenty mornings. 
Undoubtedly the explanation of this state of things is 
to be found in the enormous quantity of snow which fell 
last winter, and was still, in the middle of July, lying 8 ft. 
deep on the plateau at the base of the Medicine Bow 
1n0nnt. 
·whenever the sky was unclouded the air was usually of 
most exquisite transparency. At night multitudes of stars, 
invisible at lower elevations, were easily seen ; so that it 
was estimated that nearly all the stars of the seventh 
mag,1itude were fairly within reach of the naked eye. For 
instance, in the quadrilateral which forms the bowl of the 
" Dipper" I could see distinctly nine stars, with glimpses 
of one or two more, while at home I can only perceive 
the three brightest of them. 
The power of the telescope was correspondingly in-
creased. Without being able to devote a great deal of time 
to stellar observation, I ascertained that, with my 9!0 
inches of aperture, nearly everything could be fairly seen 
which, at the sea-level, is within the reach of a 12-inch 
object-glass. 
Some most exquisite views of Saturn will always be 
remembered, in which, notwithstanding the planet's near-
ness to the horizon, the inner satellites, and the details 
and markings of the rings, especially a dark stripe upon 
the outer ring, about a third of its width from the outer 
edge, were clearly shown under powers ranging from 500 
to 1,200. 
But in the use of the spectroscope the advantage was 
even greater. At Hanover I had been able to make out a 
list of 103 bright lines in the spectrum of the chromo-
sphere ; at Sherman the number was extended to 273 ; 
and at moments of unusual solar disturbance there were 
glimpses of at least as many more. 
Sulphur, strontium, and cerium are pretty conclusively 
shown to be constituents of the solar atmosphere. Zinc, 
erbium, didymium, and iridium are also indicated, but 
n-Jt so certainly. 
At the very base of th~ chromosphere, and to a dis-
tance of perhaps 1" or 15" from the edge of the photo-
sph<cre, it was found that tho,e dark lines which are not 
actually reversed lose their intem,ity, and vanish more or 
less completP.!y. This is substantially a confirmation of 
an old and somewhat disputed observation of Secchi's, 
who reports at the edge of the sun a layer giving a con-
tinuous spectrum. 
This is not strictly correct, however, since when the 
transparency of the air is so much increased as to cause 
the most persistent of the dark lines to vanish, a multi-
tude of the others appear reversed. There can be little 
doubt that were the effect of our own atmosphere entirely 
removed, this lowest p.:irtion of the solar atmosphere would 
give the same spectrum of bright lines which is seen at 
the beginning and end oi totality during an eclipse. 
It is noteworthy that of the 170 new lines found in the 
chromosphere spectrum, not a single one lies below C, 
and t~at for no wa'.1-t of careful examination. The only 
new Imes of much importance are the two Hs at the ex-
treme violet end of the spectrum. These were found 
almost ~onstantly r~versed, probably quite so, but the 
ob,erva~wn was so d1ffic1_1lt that we could not be perfectly 
sure of 1t on every occasion. 
vVhat is still more remarkable, it was found that these 
two lines (not the hydrogen lines, as has been erroneously 
reported) are also usually,and lam pretty confident alwavs 
reversed in the spectrum of sun-spots, not so clearly mo~e~ 
over, in the nucleus as in the penumbra, and over ,l some-
what extensive region surrounding it. ·This reversal of 
the H lines does not involve at all the disappearance of 
the dark shade, but a bright streak rather than a line 
makes its appearance in the centre of the shade which 
itself is, if anything, a little intensified. ' 
T~e spectra of several different spots were carefully 
studied, and a catalogue was drawn up of 155 lines which 
are more or less affected, usually by being greatly widened 
but in: some cases by a weakening or reversal. Severai 
© 1872 Nature Publishing Group
]Jee. r2, 1872] NATURE 
~----------- - - ------------ - - - -----
bright lines were also found in the spot spectrum, and be-
tween C and D some very peculiar shadings terminated 
sharply at the less refrangible limit by a hard dark line, 
but fading out gradually in the other direction at a dis-
tance of three or four of Kirchhoff's scale divisions. The 
interpretation of such markings is not quite clear but 
would rather seem to point to such a reduction of 'tem-
perature over the spot-nucleus as permits the formation of 
gaseous compounds by elements elsewhere dissociated, 
since these shaded spectra are quite probably charac-
teristic of non-elementary substances, a view fortified by 
Schuster's recent beautiful investigations upon the 
spectrum of nitrogen. 
Many more or less remarkable solar eruptions were ob-
served, though none on quite so magnificent a scale as 
some before recorded. On several occasions velocities of 
from 150 to 200 miles per second in the ejected matter 
were observed by means of the displacement and distor-
tion of the hydrogen lines, and on one occasion a velocity 
of nearly 250 miles was attained. One of the finest erup-
tions was visible on the surface of the sun itself in the im-
mediate neighbourhood of a large spot. 
A careful comparison of some of these observations 
with the corresponding magnetic records at Greenwich 
and Stonyhurst, for copies of which records I am in-
debted to the courtesy of Sir G. B. Airy and Rev. S. J. 
Perry, goes far to show that, although probably the 
greatest magnetic disturbances are due to terrestrial causes 
or at least are only indirectly results of solar or cosmicai 
influences, yet, on the other hand, every solar paroxysm 
does have a distinct, direct, and immediate effect upon 
the magnetic elements. Thus on August 3 such solar 
paroxysms were noted at 8.45, 10.30, and r 1.55, also on 
August 5 from 6.20 to 7.30 A.M. (Sherman time), and the 
last was the only outburst during the day. 
Now the annexed figure (Fig. 1), from a photographic 
copy of the vertical force curve for these days at Green-
wich, shows marked and characteristic disturbances at 
the points indicated, which, allowing for the longitude, 
correspond to the very instants when the solar dis-
turbance3 were noted. Further comparisons of such 
phenomena will be necessary to establish the conclusion 
with a bsolute certainty ; but in the meantime it seems 
altogether probable that every solar d isturbance receives 
an immediate response from the earth, and that the 
magnetic impulse travels with, sensibly, the velocity of light. 
I must not close -without alluding to certain ob5er-
vations that enable us to distinguish, to some extent, 
between the substances ejected from the sun, and those 
constituting the atmosphere into which the irruption 
takes place. Certain lines during these outbursts were dis-
torted and dtsplaced, while others near them, equally 
conspicuous, were wholly unaffected. 
Thus on August 3 and 5, the former class included the 
lines of hydrogen, D 3, the lines of sodium, magnesium, 
and many of those of iron ; in the latter were K534, 
1474, 1505, 1515, 1528, 1867, 2007 (1870 and 200 were in-
tensely disturbed), 2581, and probably the two Hs ; I 
say probably, because the observation of these lines was 
too difficult to permit absolute certainty, still I feel very 
confident that they were unaffected. The barium lines 
also seldom seemed to participate in any disturbance. 
The obvious moral of our summer's work seems to me 
this, that no time ought to be lost in occupying points of 
such advantage with the most powerful instruments : the 
great telescopes now building should be put in a position 
to profit by such atmospheric conditions as will secure 
their utmost efficiency, for while it is of little consequence 
to science whether ordinary glasses are placed where 
their power will be increased by 25 per cent., it may make 
a difference of years and decades in her advance if the 
new artillery opens its attack upon the heavens from the 
mountain-tops instead of from the plains. 
D.irtw.>:.1,h Colleg.c:, Nov. 25 C. A. YouNC 
THE TRANSIT OF VENUS 
AT the meeting of the Astronomical Society on 
November 8, a sketch was given of Lord Lindsay's 
preparations for the forthcoming transit of Venus. Lo!·d 
Lindsay has selected the island of Mauritius as his station, 
on account of its highly favourable meteorological condi-
tions. He intends, if possible, to combine the following 
methods of observation :-I. Observations of the internal 
contacts to be worked out on the plans of Halley and 
Delisle. 2. Observations of the first external contact at 
the chromosphere, to be made with the spectroscope. 3. 
Photographic pictures. 4. Heliometric measures. For 
the longitude it is at present intended to use the transits 
of the moon with an altazimuth made by Simms. As it 
is expected that the Germans will also have a station on 
the Mauritius, Lord Lindsay will connect his station with 
theirs by triangulation. The transit instrument is by 
Cooke, and has four inches aperture. The chronograph, 
which can be kept in motion for four hours, has four 
barrels, each of which can be worked separately, thus 
avoiding all confusion. The photographic method to be 
used is that of Prof. Winlock, who suggests a telescope of 
40 foet focal length, placed horizontally, and a heliostat 
to reflect the sun's image along it. The lens is to be an 
achromatic one. It is intended to have two planes to the 
heliostat, one mounted on a polar axis, and another to send 
the rays down the tube. Lord Lindsay has ordered a 
Foucault siderostat with 16-inch mirrors, and has obtained 
a 13-inch_ unsilvered mirror to fit the telescope to be taken 
out. He mtends to use aheliometer, though it is not much 
in favour in this country, Messrs. Respald, of Hamburgh, 
having undertaken to make one for him with all the im-
provements used in the Oxford_instrument, as well as in 
some others. The Germans intend to send one to Ker-
guelen Land, and the Russians will use it at Lake Baikal 
and the mouth of the Amoor. Lord Lindsay's will include 
the motion of the halves of the object-glass in curved 
siides, so that the images will rem<lin in focu s ; unl;mitcd 
rotation of the tube in the cradle ; the measurement of the 
position angle at the eye end, and measures of the micro-
meter read there also. Some new points are ;- the gradua-
t ion of the slides of the object-glass side by side, so as to 
be read by the same microscope; an arrangemen t to sh ut 
off light from half the object-glass, so as to equalise the 
light of the images; and the introduction of a thermometer 
at the end ?f. t!1e tube. Lord Lindsay proposes to eliminate 
erro;s of d1v1s1on as affected by temperature, by placing 
the mstrument on one of the collimating piles of his transit 
circle at home, and heating the room by gas to different 
temperatures. It is hoped that, by taking a large number 
of measures, and by taking the most careful precautions, 
the original error of observation may be reduced to less 
than 0"·5, and thus make the result one of extreme accu-
racy. 
Lord Lindsay will be glad to receive the advice and 
assistance of astronomers accustomed to use the helio-
meter. Mr. D. Gill will accompany Lord Lindsay, the two 
dividing the work of observing between them. 
THE "CHALLENGER" 
ON Friday last, Dec. 6, several members of the council and "the Circumnavigatino- Committee" of the 
~oyal Society, by invitation of the ~ords of the Admiralty, 
111~pected at Sheerness H.M. ship C/1alle11ger, which 
sailed on Saturday on her three or four years' scientific 
circumnavigating expedition. The Government have all 
along cohsulted the Royal Society as to the fittino- out of 
this expedition, and have liberally carried out"' every 
sugg~~t~on made by the Circumnavigation Committee. 
The v1s1tors to Sheerness on Friday included many dis-
tinguishod men Qf science, among th em bei ng S ir \Vii 1ia:n 


The Sherman astronomical expedition

Dartmouth College 
Dartmouth Digital Commons 
Dartmouth Scholarship Faculty Work 
1-1-1871 
The solar aurora theory 
C. A. Young 
Dartmouth College 
Follow this and additional works at: https://digitalcommons.dartmouth.edu/facoa 
Dartmouth Digital Commons Citation 
Young, C. A., "The solar aurora theory" (1871). Dartmouth Scholarship. 4075. 
https://digitalcommons.dartmouth.edu/facoa/4075 
This Letter to the Editor is brought to you for free and open access by the Faculty Work at Dartmouth Digital 
Commons. It has been accepted for inclusion in Dartmouth Scholarship by an authorized administrator of 
Dartmouth Digital Commons. For more information, please contact 
dartmouthdigitalcommons@groups.dartmouth.edu. 
© 1871 Nature Publishing Group
NATURE 345 
moon and full moon, at the boundary plane appertaining to the 
moon. The result is that all parts of the mass are perpetually 
undergoing considerable cross-strains, for the forces of tension 
and con1pression will not relieve each other, as they act at right 
angles to one ano'her. 
If tbe mass of the eanh were not rigid, but sufii.ciently 
elastic, like, for instance, a globe of india-rubher, the particles 
would yield to their small disturbing forces ; and the result would 
be that each particle, as it arrived by rotation at each point of its 
circuit, would move in proportion to the force acting on it, one 
way or the other. In this case there would be nothing to cause 
the axis to move; the earth would steadily revolve, and no pre-
cession or nutation would occur. The whole mass would, as it 
were, breathe, heaving its surface and drawing it in again in 2 
complicated undulation. 
But observation shows that the earth has precession and 
nutation ; and therefore the mass cannot be thus elastic. 
If it be only partially rigid, then there would be a correspond-
ing degree of yielding; but precession and nutation would still 
be produced, and a strain, in a somewhat diminished degree, . 
affect the mass 
Now, mathematical calculation made on the hypothe,is of 
the earth's mass being absolutely rigid, and that throughout, 
shows that the annual precession would be 51 ·3566".* Astrono-
mical observation shows that the precession is actually 50·1". 
The remarkable nearness of these results is sufficient proof that 
the earth's mass is not the limp thing some take it to be ; all 
viscous-fluid from only roo miles down to the centre, moving so 
slowly, that it gives inertia to the hard crust (supposed thin) as 
if it were all solid ! It is more like the highly rigid mass which 
Sir William Thomson has shown it to be from other conside-
rations. JOHN H. PRATT 
Calcutta, July l 5 
Meteorology in South Australia 
As it may be interesting to some of your English readers to 
hear something of natural phenomena in such an out-of-the-way 
part of the world as South Australia, I forward a description of 
three very fine meteors which have lately been seen here, as well 
as a splendid display of Aurora Australis. 
On January 5th, 1871, at about half-past nine P.M., I observed 
a splendid meteor. It appe~red at first l_ike a fixed st~r abo:1t 
three times as large as J up1ter, or say six or seven mches m 
diameter, and was probably about 15° above ~he hori~on, or nearly 
of the same apparent height as a large star which was JUSt below the 
planet Jupiter, a little to the west_ of him and w\t~in half an hour 
of the meridian. The meteor, w h1ch was very bnlhant, somewhat 
of the appearance of Jupiter, remained apparently stationary for, 
at least five seconds; it then gradually began to move from a 
due no:tl1 position to a direction about S.S.E., and in a horizon-
tal line ; it then burst into several smaller meteors and went out, 
having lasted fully twenty _sec,,nds altogether. The moon was 
shining brightly at the time, being a few days off the full. 
On the same night, and at about the same hour, a large meteor 
was seen by a survey party at Hookina, a place about 400 miles 
north of Adelaide. The surveyor in charge of the party (Mr. 
Hamilton) from whom I obtained the particul_ars ~f this meteor, 
says he was facing the east when he observed 1tgomg _from N.E. 
to S. E., describing a large arc at an apparent. elevat10~ of 20°. 
He describes its colour as greemsh, and so bright that it almost 
overpowered the light of the moon. It ultimately burst with a 
loud explosion into a number of fragments of red and blue 
colours, and the earth was felt to tremble as· though a shock of 
an earthquake had occurred. 
On the 25th March last, at about twenty minutes to three 
o'clock in the afternoon, I observed a meteor in the full blaze of 
the sun. It appeared like a bright brass-coloured ball of fire, 
shooting through the sky like a rocket; it seemed to have a green 
and blue light round a central brass-coloured nucleus. The 
meteor appeared about three inches in diameter; it had a whitish 
comet-like tail, about three feet long, and it came from the 
N.N.E. and travelled downwards towards the S.S. \V., so that 
as I was looking south it appeared to come over my left shoulder. 
It lasted about ten seconds, then burst without noise, and became 
dissipated. This meteor seemed to fall at about 15° from the 
horizon. _ 
In the S. A. "Register," a few days after seemg the last 
..,. See this worked out in my" Mechanical Philosophy," 1st edit. p. 562, 
2nd edit. p. 540. 
described meteor, it was stated that a surprising sound was 
heard at Point Macleay, and other places about fifty or sixty miles 
to the south-east of Adelaide as of the firing of cannon, and the 
correspondent of that paper at Mannum (a place on the River 
Murray, about sixty miles east of Adelaide) writes as follows ·:-
" On Saturday last (25th March) at exactly 2.45 P.M., I was 
looking down the Murray River, when suddenly my attention was 
attracted by a large ball of fire falling from the heavens in almost 
a perpendicular course. The lakes are from here in the direction 
which it indicated-almost due south-so that I have no doubt 
the extraordinary phenomenon mentioned as having occurred on 
the shores of Lake Alexandrina, may have arisen from one of the 
caw es assigned, viz., a falling meteor or an aerolite. What I 
saw was evidently the explosion immediately preceding the fall, 
and it presented the appearance of a luminous meteor." . . . . 
The display of " aurora australis" which I observed on the 
23rd March last, commenced at about eight o'clock P.M. It 
increased in brightness till eleven o'clock, when it gradually faded 
away. At about two o'clock AM., while at a ball, I came out on 
the balcony and observed the whole southern sky lighted up by 
a most gorgeous display of aurora. It occupied about 70° or 
80° of the horizon, extending from about S.S.E to S. W., and 
reached to a heightof say 60° above the horizon. It was of a 
splendid red rose colour and streaked with beams of white light 
at various distances apart-say two bands of white in every 10°. 
These white bands appeared about two feet to five feet wide, 
which would answer to say 5° observed by the eye alone. The 
display was so bright that by placing my hand with the fingers 
apart at -about two feet from a lady's white dress, I could dis-
tinctly see the shadow of each finger •. This aurora was also seen 
in Victoria and New South Wales. 
I may mention that Adelaide is situated in south latitude about 
35°, and longitude 138° 401 M. M. FIN NISS 
Adelaide, June 19 
The Solar Aurora Theory 
IN the very interesting lecture of Mr. Lockyer upon the recent 
solar eclipse which has just appeared in NATURE, he says, 
speaking of the green line layer above the hydrogen, "Here 
obviously we have, I think, merely an indication of another 
substance thinning out, in spite of the extraordinary suggestion 
which was put forward that the corona was nothing but a per-
1nanent solar aur01~a." 
I agree entirely in this view except as to what would seem to 
be implied by the expression in spite oJ: I fail to see any incon-
sistency between the idea of a substance " thinning out" and a 
permanent solar aurora. 
What I intended in adopting and endorsing this auroral hypo-
thesis was simply this : to express the belief ( which I still hold, 
though with no great tenacity) that the substance which com-
poses this green-line layer is also found in the upper regions of 
our atmosphere in a state of almost inconceivable tenuity, and at 
an elevation of certainly more than one hundred miles ; and, 
further, that the peculiar filamentary and radiant structure of the 
corona, and very possibly its luminosity to some extent, are due 
to solar forces closely analogous to those which produce our 
terrestrial auroras. 
Or in other words, that an observer, at the planet Mars for 
instance, looking at the earth during a period of auroral activity 
would see its poles capped by a corona in substance, structure, 
and to some extent in origin, closely analogous to that which is 
permanent around the sun. 
And if we grant the identity of the 1474 line with that which 
is, to say the least, so closely coincident with it in the auroral 
spectrum, it is difficult to see why the hypothesis should be con-
sidered "extraordinary," or per se improbable. 
·That the enormous chemical, thermal, luminous, and magnetic 
activity of the solar surface should be unaccompanied by mani-
festations of what we call electric energy seems far more unlikely 
than the contrary ; and if such energy operates we shou!d n_aturally 
look for phenomena,. the counterparts of those by which 1t shows 
itself here, but on the solar scale of course. 
As to the identity of these lines, however, there may fair~y 
remain some doubt. This line in the spectrum of the aurora is 
so rarely seen so faint and so difficult of observation, that, al-
though the fe;_, observ;tions thus far ob~ained_ s~ow e_ve~ a sur-
prising agreement with each other and with this idea, 1t 1s safer 
to maintain a cautious reserve. C. A. YOUNG 
Dartmouth College, U.S.A., August 16 


The solar aurora theory

Dartmouth College 
Dartmouth Digital Commons 
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1-1-1871 
An explosion (?) on the sun 
C. A. Young 
Dartmouth College 
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© 1871 Nature Publishing Group
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