
Sept. 7, 1871| 
MAT ORE 
373 

and then describing a circle, to represent a section through 
_ the axis of the earth so that the magnet shall occupy the 
central part, about two-thirds of its diameter. The por- 
- tion of the magnetic curves outside the circle will cut the 
circle at different angles, and fairly represent the directions 
of the auroral streamers. 
Now, Arago, in his catalogue of auroras, shows that 
during the months of September, October, March, and 
April we are especially favoured with auroras; and that 
in these months they are both brighter and more frequent 
than at other times. This periodicity indicates an extra 
terrestrial origin for auroras. Does it not show that 
during those months we pass through an auroral region, 
just as in November and August we pass through meteoric 
regions, or, in other words, that we intersect aring of some 
substance capable of being electrified by the earth in its 
passage, when there is any change in its magnetic power, 
and so rendered luminous? But itis impossible not to con- 
jecture that this ring or disc is the very disc which is 
visible to us as the zodiacal light ; for besidesthe fact of zodi- 
acal light being specially visible during the same months, 
there is the positive evidence of spectrum analysis to the 
identity of the substances luminous in the aurora and the 
zodiacal light. Weare led then to the hypothesis that 
there exists round the sun, and extending as far as our 
earth, an atmosphere, consisting of an unknown element, 
a gas of extreme lightness, and that this atmosphere is 
especially condensed in the form of a disc extending round 
the sun, but probably not concentric with it. The same 
element appears to exist in the solar corona, and was also 
detected in the vague phosphorescent luminosities of the 
sky on a particular evening, by, I think, Angstrom. 
I wish to suggest, therefore, that catalogues of auroras 
may, like catalogues of meteors, determine auroral regions 
in the earth’s orbit, and that two such regions are, in fact, 
already shown by Arago’s catalogue, and that this periodi- 
city, as well as the results of spectrum analysis, indicate a 
cosmical origin for auroras. 
There is one more point which may be interesting. The 
luminous streamers have a lateral motion ; they shift side- 
ways, and in fact rotate round their pole. Is this motion 
of rotation always, or even generally, in the same direc- 
tion? I have not observed it often enough to speak with 
confidence. But if so, it must have some definite cause, 
and will be analogous to that of rotation in a definite 
direction of an electrical current round the pole of a 
magnet. The earth must be looked upon as a delicate 
solar electroscope and magnetometer, and the electrical 
discharge round the earth is stratified, and is in lines and 
strata that have, perhaps, motions in definite directions, 
It may be worth remarking that the 22nd, 23rd, 24th, 
and 25th of October are the most famous days in the year 
for auroras, at least in the present century, and that the 
greatest displays of all on those days have happened at 
intervals of multiples of eleven years. Last year we had 
splendid auroras on the 24th and 25th; there is, there- 
fore, some ground for expecting fine auroras on the same 
nights this year, if the auroral cycle corresponds to the 
sunspot and magnetic cycles. J. M. WILSON 


NOTES 
WE learn from Indianapolis journals, received at the moment 
of going to press, that the American Association for the Advance- 
ment of Science commenced its sittings on the evening of August 
21 by an opening address from the retiring president, Prof. T. 
Sterry Hunt, on the Iron Interests of Indiana, in which he com- 
pletely sustained every claim that had been made for the State, 
showing conclusively that it has the elements within its borders 
from which to secure a manufacturing future that shall make 
Indiana the mediterranean workshop for the whole country. The 
sections commenced their sittings on the following day, and San 
Francisco was fixed on as the next place of meeting. An extra 


double number of the American Naturalist for September 15 will 
give a full report of both the opening address and the sectional 
proceedings. Ina future number we shall give an epitome of all 
matters of interest discussed at the meeting. 
M. JANSSEN has been commissioned by the French Govern- 
ment to proceed to the East to observe the total Solar Eclipse of 
December next. He has, therefore, been compelled to decline 
the offer made to him by the British Association to take part in 
the British Expedition. 
THE President of the Royal Society has received a telegram 
from the Government Astronomer, Melbourne, that the Eclipse 
Expedition will leave that port on November 20, 
WE regret that owing to the omission of a sentence, the note 
respecting the distinguished visitors at Section A of the late 
meeting of the British Association, read incorrectly in a small 
proportion of the edition of our last number. We now supply 
the omission by giving the following probably unexampled list of 
Senior and Second Wranglers and Smiths’ Prizemen who were 
present :—Adams, Cayley, Challis, Stokes, Hon. J. W. Strutt, 
Hopkinson, Kelland, Tait, Wilson, Thomson, Maxwell, 
Sylvester, Clifford, Jack, J. W. L. Glaisher ; of these the first 
nine were Senior Wranglers. 
WE learn from the British Medical Fournal that in accordance 
with the will of the late Dr. Lacaze a prize of 10,000fr. is to be 
awarded by the Faculty of Medicine of Paris every second year 
to the best work on phthisis and on typhoid fever alternately. 
The first prize will be awarded at the end of the academical year 
1871-2, for the best work on phthisis. Essays (with a distin- 
guishing motto and the author’s name in a sealed envelope) must 
be sent in before July 1, 1872. The prize is open to foreigners. 
IN a paper read before the Natural History Society of Boston 
(U.S.), Mr. W. T. Brigham gives an account of several remark - 
able earthquakes that have occurred in New England, with a list 
of all such phenomena that have occurred in that region from 
1638 to 1870. Some of these disturbances appear to have been 
violent and protracted. 
WE understand from the Geological Magazine that there will 
shortly be published a Geological Atlas of England, by Mr. W. 
Stephen Mitchell. The Atlas will contain the following Maps :— 
I. Cambrian (of Survey); Lower Cambrian (of Sedgwick). 
2. Lower Silurian (of Survey) ; Middle and Upper Cambrian 
(of Sedgwick). 3. Upper Silurian (of Survey); Silurian (of 
Sedgwick). 4. Old Red Sandstone; Devonian. 5. Carbon- 
iferous Limestone; Yoredale Beds. 6. Millstone Grit ; Coal 
Measures. 7. Permian (of Survey) ; Pontefract Group (of Sedg- 
wick). 8. New Red Sandstone; Rheetic,(Penarth). 9. Lias, 
10, Lower Oolite. 11. Middle Oolite. 12. Upper Oolite. 
13. Wealden; Neocomian. 14. Gault; Upper Greensand ; 
Chalk and Chalk Marl. 15. Eocene. 16. Crag. 17. Al- 
luvium. 18. Bone Caves. 19. Metamorphic (?) 20. Igneous. 
The Maps will be printed in colours, each Map exhibiting only 
the range of one formation, and the names of places on the for- 
mation. In some few cases, where it is requisite, as a clue to 
the locality, to introduce the names of places near, but not on, the 
formation, these will be printed in a different type. The Maps 
(11 fin, by gtin.) are based on a photographic reduction of the 
last edition of the Greenough Map, which is published under the 
direction of a committee appointed by the Geological Society. 
In all cases where, through researches more recent than this last 
edition, any changes have been adopted in the grouping of the 
beds, this atlas conforms with the latest alterations. The revision 
of the proofs of particular maps has been kindly promised by 
Mr. W. Boyd Dawkins, F.R.S., Mr. W. Whitaker, Mr. H. 
Bauerman, Mr. J. W. Judd, Mr. Charles Moore, Mr. W. T. 
Aveline, and others. Letter-press will accompany each map, 
giving in a tabulated form the subdivisions of the formations, the 
