May 11, 1871] 
NATURE 
27 

Mr. F. J. Evans also refers to the vast amount of animal life, 
and mentions the quantities of sharks and a//igators which 
abound in and about Greytown Harbour. I can fully cor- 
roborate this, although I believe that what Mr. Evans terms 
alligators are really crocodiles (Molinia Americana), 1 should be 
glad to have certain information on this point : when not actually 
visible, their proximity is made evident by a powerful odour of 
musk. The most notable, however, of the denizens of these 
waters, besides the turtle, is the Atlantic manatee, which 
Columbus mistook for a mermaid, and which Agassiz terms the | 
modern representative of the Dinotherium. The Mosquito 
Indians on the Indian, Rama, and Blewfields rivers are great 
adepts at harpooning this paradoxical mammal, and its flesh salted 
is a staple article of food all along these coasts, being not unlike 
to ship’s pork. 
Southsea, April 28 S. P. OLIVER 
P.S.—When at anchor off Greytown, also in the Danude 
steamer, during the night of February 15, 1867, (moon eleven 
days old) there was no vibration or noise perceived, but then 
there was a tremendous swell breaking with high surf on the bar, 
and the vessel rolling heavily. It would be interesting to over- 
haul the logs of the Royal Mail Company’s vessels which have 
been at Greytown, in order to discover the periods of these vibra- 
lions, but I am afraid that no observations have been recorded 
4 in their books. 
Mechanical Equivalence of Heat 
You will see from the proceedings of the Literary and Philo- 
sophical Society at Manchester, that, since the discussion there, 
Dr. Joule has definitely abandoned the reasonings in his famous 
paper on the mechanical force of electro-magnetism, steam, and 
horses. I have now had time to test the facts and experiments 
of this new theory, and findit, as I hope soon to show in detail, 
as untenable as his former one. Indeed, I am sure that the 
mechanical equivalence of heat must soon be generally abandoned 
as inconsistent with facts. You will see that the April number 
of the ‘‘ Review of Popular Science,” has definitely pronounced 
a decision in my favour ; and I am sure you will soon be con- 
vinced yourself that your own first reviewer of my article in the 
Quarterly Journal of Science was more reasonable than your 
second, H, HicHron 
Aurora by Daylight 
AN additional well-authenticated instance ot this very rare but 
indisputable phenomenon, may, perhaps, be thought worthy of 
insertion. 
In the Transactions of the Royal Irish Academy for 1788 
(embodied in ‘*Memoirs of Science and the Arts,” 1798), is 
“An Account of an #Aurora Borealis seen in full Sunshine, by 
the Rey. Henry Ussher, D.D.,” which opens in the ensuing 
manner :— 
“The following phenomenon being very uncommon, if not 
entirely new, I think it worth communicating to the Academy, 
principally with a view to learn whether any other person has 
observed a similar one at any time :— 
*©*On Saturday night, May 24, 1788, there was a very bright 
aurora berealis, the coruscating rays of which united, as usual, 
in the pole of the dipping needle. I have always observed that 
an aurorz borealis renders the stars remarkably unsteady in the 
telescopé The next morning, about eleven, finding the stars 
flutter much, I examined the state of the sky, and saw whitish 
rays asceading from every part of the horizon, all tending to the 
pole of tie dipping needle, where at their union they formed a 
small thin and white canopy, similar to the luminous one ex- 
hibited by an aurora at night. These rays coruscated or shivered 
from the horizon to their point of union. These effects were 
distinctly seen by three different people, and their point of union 
markedseparately by each of them,’” 
T, W. WerspB 
{ 
The Coronal Rifts 
THE :nclosed extract of a letter from Captain Tupman, who 
observel the Eclipse of December last through the finder of Prof. 
Marknes’s telescope at Syracuse, may interest some of your 
readers — 
“Tt % asingluar feature in all the photographs that the ‘ rifts’ 



are so wide and distinct. They are actinic rifts. As seen in 
the telescope simply the corona had no such rifts. I watched 
it during the whole 105 seconds ; such a feature would, of course, 
have struck me instantly, I actually pointed Prof. Harkness’s 
spectroscope 77 the rifts as being bright parts of the corona !” 
A. C. Ranyarp 
The Name “ Britain” 
As “C. L. N. F.” has in your last well answered the letter of 
“A, R. H.,” I have now only to reply to Mr. Hyde Clarke’s 
letter, in which he says I should find it difficult in my derivation 
of ‘‘ Britannia” and ‘‘tin” ‘to explain on the same basis the - 
conformable names’’ of the countries and rivers which he men- 
tions, inasmuch as ‘‘ these names are not explainable in Phoeni- 
cian, because they were given long before the Phcenicians entered 
on the stage of history.” 
His paper read before the Anthropological Institute I have not 
seen, but as ‘‘ the learned” Bochart and other authors have con- 
sidered the name ‘‘ Britain” to have been derived from the tin 
which the Phcenicians exported from Cornwall more than 3,000 
years ago (Num, xxxi. 22), and as no one will venture to say that 
“tin” was not then the name of this metal in the most ancient 
Cornish as well as in the Phcenician language, from which it 
proceeded, I do not think T can fairly be called upon to go into 
the “difficult” task suggested by Mr. Clarke. 
The original name of, our island I have imagined to be Bretin 
(‘Tin Mount”), that being at first exclusively the name of the 
mount from which the Cornish 4 was exported by the Pheeni- 
cians, and it is highly probable that the same name was after- 
wards given by these ancient traders to the entire island, otf 
which the mount was only a part, for it was Britain that gave 
them nearly all their /, and its most beautiful natural object 
known to them was St. Michael’s AZound/. 
There being other islands close to Britain, the Romans gave 
the name Arifannic indiscriminately to them all. When they 
spoke of Britain as dissociated from its contiguous islands, they 
called it either Britannia or Insula Britannica, which is synony- 
mous with vijros Bperravien. This word, Bperravien, used at 
first adjectively by the Greeks, had in the time of Diodorus 
Siculus become a substantive, so that he uses it as such when 
describing the daily insulated port or mount called sometimes 
Li:tin (Tin Port), and sometimes Breti (Tin Mount), adjacent to 
Bperravucn, to which port or mount at low water the tin was 
carried from the mainland for sale and exportation. The follow- 
ing is the passage :—eis rqv ynrov mporemerny ey THs Bperravucns 
ovomaComevny de “Int, 
Plymouth, May 6 RicHARD EpMONDs 
*“ We cannot print any more letters on this subject. —En, 
The Sensation of Colour 
Pror, CLERK MAXWELL in his valuable paper on Colour in 
NATURE (vol, iv. p. 13) commits himself to the opinion that there 
must be three distinct sets of retinal nerves, one for each of the 
three primary sensations of colour. It is obyious that demon- 
strative proof or disproof of this is unattainable: we can only 
reason analogically. ‘The analogy of the ear is in favour of such 
an opinion, so far as it goes ; for there appears to be proof, or 
probability almost amounting to proof, that sounds of different 
pitch are conveyed to the brain by different nerves. But the ear 
resembles the other organs of sense less than they resemble each 
other ; and there is surely no reason for thinking that there are 
distinct nerves of smell for every distinct kind of smell, or distinct 
nerves of taste for every distinct kind of taste. Nor I believe 
is there the slightest proof of nerves for the sensation of heat 
distinct from those of touch, 
JosErH JOHN Murpuy 
Old Forge, Dunmurry, Co, Antrim, May 8 
P.S.—I am not now at home. I intend to write in reply to 
Mr. Laughton’s important letter on the Prevalence of West Winds, 
when I am at home and have the file of Nature and other 
authorities to refer to. 


The Cave-Lion in the Peat of Holderness 
WHILST engaged in the task of rearranging this Museum, I 
have been impressed with the value of two specimens in the 
Paleontological collection. 
One is labelled ‘* No, 7, /e/is—metatarsal inner (Right side),” 
