a 
eee eee eee 
Dee, 1870 | 
NATURE 
87 

It is improbable that these are anything but a fraction of Dr. 
Nicholson’s etymological misrepresentations. Mistakes in the 
glossary of a zoological work are not of very great importance, 
and would not in this case have demanded notice had they not 
been fair samples of the general character of the book in which 
they occur. 
I much regret that the fact of the writer’s name being appended 
to the notice of Dr. Nicholson’s work should have led him into 
the region of personalities, whither I do not intend to follow 
him. E. Ray LANKESTER 

Glass Floats off the Isle of Lewis 
Ir would be of great importance if the /ac¢ could be ascertained 
whether the floats are from the Norwegian or from the Canadian 
fisheries. Your note of November 10 says, ‘‘ They are 
hermetically sealed, and have certain characters, such as IV. or 
VI., impressed on the sealed part.” Doubtless your columns are 
read in Norway as well as in Canada, and possibly a correspon- 
dent, from these characters or from other evidence, may claim 
the floats for one or for the other side of the Atlantic. In favour 
of the west side, but with the utmost deference to the opinion of 
Mr. Gwyn Jeffreys, I suggest that a north-eas¢ wind is an unlikely 
conveyance to ‘the west side of the Island of Lewis,” or to 
“the western coast of Shetland.” 
A writer in the Atheneum of this week (Nov. 19, p. 659) 
thinks that these ‘net floats” are carried to Nova Zembla, and 
“still farther to the north and east” by the Gulf Stream. Dr. 
Carpenter supposes a constant warm surface current from each 
tropic to each pole, and a constant cold current below from each 
pole to each tropic,caused as we cause the currents of water to 
warm our houses. Suppose this grand theory to be true. The 
surface current should warm east coasts as well as west coasts. 
The same parallel touches England, Newfoundland, and Van- 
couver’s Island. The climate of England and of Vancouver’s 
Island on west coasts is “‘ insular.” The climate of the és/and of 
Newfoundland on an east coast is ‘‘ excessive.” This difference 
of climate in islands, on the same parallel, at the same levels, 
results from currents of av, not from currents of watey—namely, 
from the prevalence of south-west winds in the north temperate 
regions. In winter with a south-west wind we hunt, with a 
north-east wind we skate. 
GEORGE GREENWOOD, Colonel 
Brookwood Park, November 19. 


ENGLISH GOVERNMENT ECLIPSE 
EXPEDITION 
ee arrangements and instructions are not yet 
finally completed, but it is thought that the latter 
may be useful to members of other Expeditions, though 
they are not yet by any means complete. 
A. SPANISH AND ALGERIAN PARTY. 
NorTr.—. his party leaves Portsmouth in the “* Urgent,” on the 
6th proximo. Observers to be on board by 5 P.M. on the 5th. 
1. Cadiz Detachmenl.—In charge, the Rev. S. J. Perry. 
Spectroscope, the Rev. S. J. Perry and assistant (Mr. 
Hostage), Mr. Abbay; Polariscope, Mr. Moulton, Mr, 
Hudson: Sketches of Corona, Mr. Naftel, Mr. Smyth, 
Mr. Penrose, Mr. Collins; Time and General Obser- 
vations, Captain Toynbee. 
2. Gibraltar Detachment.— In charge, Captain Parsons. 
Spectroscope, Mr. Carpmael, Mr. Gordon; Polariscope, 
Mr. Lewis, Mr. Ladd ; Photography, Mr. Buckingham, 
and assistant (Mr. Spiller); Sketches of Corona, Mr, 
Hunter, two Oxford men; Saturn in the Corona, Mr, 
Talmage, Mr. Maclear ; Chemical Intensity, Mr. Thorpe. 
3. Oran Detachment—In charge, Mr. Huggins. Mr. 
Huggins, Admiral Ommanney, Rev. F. Howlett, Mr. Car- 
penter, Mr. Crookes, Captain Noble, Dr. Gladstone, 
Prof. Tyndall. 
B. SICILIAN PARTY. 
Note.—T7his Party leaves London, overland, at 8.45 P.M. from 
Charing Cross, on the 7th proximo. 
In charge, Mr. Lockyer. Spectroscope, Mr. Lockyer and 
assistant (Mrs. Lockyer), Prof. Roscoe and assistant (Mrs. 

Bowen), Mr. Seabroke and assistant (Mr. Burton), Mr. 
Pedlar ; Polariscope, Mr. Raynard, Mr. Griffith, Mr. 
Clifford ; Sketches of Corona, Mr. Brett, Mr. Darwin ; 
Photography, Mr. Brothers, Herr Vogel, Mr. Harris; 
Time and General Observations, Mr. Vignoles, Sen., 
Mr. Vignolles, Jun. 
INSTRUCTIONS TO OBSERVERS. 
Instructions for the Polariscopic Observations of the 
Corona, including Beams and Streamers.—\t is recom- 
mended that the polariscopic examination of the Corona 
be carried on as follows :— 
1. To examine a detached and selected part of the 
Corona about 6’ from the limb of the sun, and say about 
8’in diameter. 2. A field extending from the limb of the 
sun outwards should be examined either with a Nicol’s 
prism, or a double image-prism. 3. The light of the 
streamers at some distance from the sun should be 
examined with a Nicol and a crystal. 4. The polarisa- 
tion of the Corona should be examined in such a manner 
as to eliminate atmospheric polarisation. of¢e.—The 
most suitable instruments for ascertaining the plane of 
polarisation, and the proportion of polarised to unpolarised 
light are (1) a double-image prism ; (2) Savart’s polari- 
scope ; (3) a plate of quartz, consisting of two compensa- 
tion wedges turned through an angle of 180° ; (4) a plate 
of arragonite, or calc spar, cut perpendicular to an optic 
axis, and affixed to an analysing prism ; (5) a polarimeter, 
consisting of four plates of glass, movable on an axis per- 
pendicular to the plane of polarisation. 
Furst Observation.—The object of this observation is 
to observe the polarisation (if any) of the Corona without 
having the observer’s attention distracted by the chromo- 
sphere. A Savart’s polariscope is recommended by pre- 
ference. The Nicol’s prism of the polariscope should be 
set beforehand with its principal plane (or plane of symm- 
metry) radial, z.c. perpendicular to the sun’s limb, and the 
observer must note whether bands are visible, and if so, 
whether they are black-centred or white-centred. Should 
the bands be feeble, it will be well to rotate the polariscope, 
prism and plates of course moving together, and quickly 
restore it to its primitive azimuth, after having noted the 
estimated azimuth of the Nicol when the bands are 
strongest and black-centred. Should no bands, or only 
dilute bands be seen, it may be that the Corona, though 
polarised, is overpowered by other light; and the ob- 
server will move the telescope from the sun, radially if it 
may be, if in any other direction rotating the polariscope 
so as to render its principal plane radial in the new posi- 
tion. He will then note whether, though the light becomes 
feebler, the bands become less dilute. Should, on the 
other hand, the bands be strong, the observer, after 
having satisfied himself as to the plane of polarisation, 
will endeavour to make out whether by means of the 
polarisation of its light the Corona can be detected super- 
posed on the chromosphere. He will, therefore, move 
the telescope /owards the sun, keeping the principal plane 
of the polariscope radial, and note how near the sun the 
bands can still be seen. To provide for the contingency 
of this observation, it will be well to point in the first 
instance to the side of the sun which will be first un- 
covered. If time permit he should try whether there is 
any sensible quantity of polarised light on the dark disk 
of the moon, rotating the analyser and determinating the 
plane of polarisation. 
Second Observation.—The special object of this obser- 
vation is to differentiate, if possible, between the Corona, 
on the one hand, and the Chromosphere, or whatever else 
may be self-luminous (be it even a portion of the Corona it- 
self), on the other. This will be possible if the light of 
the Corona be strongly polarised, so as to admit of com- 
parative extinction by an analyser. The observer should 
turn the analyser so as to extinguish, as far as may be, 
the light of the Corona in the neighbourhood of a radius 
