c= : ° 
68 
1 
also tapers down to about the thickness of a straw, and here 
there is no calcified axis. A thin section of the stem in its 
thickest part showed that it had been formed in concentric 
layers which were perfectly circular and presented nothing corres- 
ponding to the stellate arrangement of the sarcode. These rings 
undoubtedly represent different phases in the life of the animal. 
I have counted as many as thirteen in one section, and should 
they indicate animal deposits, this would give us thirteen years 
as the time required for their formation, a period not too long 
when we consider the length (upwards of seven feet) which some 
of these stems have attained. Whether this specimen is new I 
am not prepared to state, and shall not therefore name it, although 
I believe it has not been before observed. Its generic relations 
will, I think, be with Hyalonema and Euplectella, both sponges 
of the Pacific.” James BLakE 
San Francisco, Oct. 27 
Misleading Cyclopzdias 
CAN any of your readers inform me if there is such a thing 
as a good and honestly constructed cyclopzedia—one that does 
not send you hunting for information from one volume to another, 
and refer you backwards and forwards to articles that do not 
exist ? 
I have been repeatedly annoyed by this kind of will-o’-the- 
wisp, but have to-day met with such an outrageous example of 
it, that, although it involves some trouble, I feel it to be a duty 
to make a public exposure of it in your columns. 
Requiring some facts on unusual atmospheric refraction, I 
turned to ‘‘ Refraction ” in the ‘‘ English Encyclopedia.” This 
article referred me to ‘‘ Mirage, Fata Morgana,” &c., for informa- 
tion on this branch of the subject. Turning to ‘‘ Mirage,” I 
found not a word, but another reference to ‘‘ Reflection and 
Refraction, Atmospheric, Extraordinary.” Next I tried “Fata 
Morgana,” again the same reference. Coming back to letter R, 
I found the article ‘‘ Reflection and Refraction,” but was here 
referred to ‘‘ Light, Optics, Refraction, Refrangibility ;” then to 
letter A, ‘‘ Atmosphere, Atmospheric”—nothing on the ‘sub- 
ject. Letter E, ‘‘Extraordinary Refraction”—nothing but a 
reference back again to “ Mirage!” “Light, Optics, and Re- 
frangibility ” contain ncthing on the subject. : 
I was thus sent on a search through five volumes of the work, 
and made to hunt out nine distinct headings for what does not 
exist ; and what makes the matter worse is, that the writer of the 
article “‘ Refraction,” at the end of the work, must have sown 
that it did not exist when he referred back to ‘‘ Mirage, Fata 
Morgana,” &c., which words have not a word of information 
appended to them. 
An alphabetical cyclopzedia is somuch the most convenient for 
reference, and might be such an invaluable addition to a library, 
that it is the more to be regretted that it should be brought into 
disrepute by the absence of all efficient editorial supervision. 
; A, R. WALLACE 
Rainbows on Blue Sky 
In Nature for Noy. 21 a correspondent asks for examples of 
bows seen on a cloudless background. 
T have seen this phenomenon twice at least. In one instance 
I remember that the extremities of the bow were seen against 
cloud, while the central portion bridged a space of clear blue 
sky. 
i more perfect example occurred on the 19th of February in 
the present year. The following is a verdatim extract from my 
notes of that day :— 
“Peculiar rainbow at 11.50 A.M. ; perfect (except quite near 
the extremities), fairly bright, but projected throughout its entire 
length against clear blue sky. No rain was falling at the time, 
nor was there any appearance of falling rain on the sky, but the 
character of the clouds and of the weather was consistent with 
the supposition of slight and partial showers.” 
The phenomenon, although rare, does not seem to call for any 
special explanation. In showery weather, especially with a low 
barometer, one may sometimes see rain falling from a mere shred 
of cloud, the sky round about being clear. In such a case it is 
evident that there may be places whence an observer would see a 
rainbow against blue sky. Even should there be no visible cloud 
from which the rain seems likely to have fallen, the same ex- 
planation will still serve, for the cloud may be too attenuated to 
be visible, or may indeed be actually exhausted, the rainbow 
being formed on its last drops. 
NATURE 
‘[Mov. 28, 1872 
iw: 
- 
It scarcely needs to be pointed out, that'when a rainbow is 
seen, as it usually is, against a cloud, the presence of the cloud 
is accidental rather than essential, the bow being formed not on __ 
the cloud, but on the drops of falling rain, and those being gene- 
rally much nearer to the observer than the cloud. , 
Clifton, Noy. 25 GrorGE F, BURDER 
The Greenwich Date 
I Am anxious to obtain the solution of a question which has 
for some time perplexed me, and which is rendered more press- 
ing than formerly, now that telegraphic communication is esta- 
plished between England and Australia. a 
It appears that a telegram sent on October 21, 3h. 5m. mean 
astronomical time at Adelaide, was received on October 21, 
21h. 40m. mean astronomical time at Greenwich. Now, to ob- 
tain the Greenwich date of its despatch, we apply the longitude ~ 
in time, adding when the place is west of Greenwich, and sub- 
tracting whenit is east. Adelaide is gh. 35m. east of Greenwich, 
the date sought is October 20, 18h, 10m. But suppose a place 
gh. 35m. west of Greenwich, then the date sought comes out 
October 21, 13h. 10m., that is to say, the result of the operations 
gives a difference in the day of the month at places where, in 
fact, the day of the month must actually bethe same. The query 
then is—in what part of the globe, and in what meridian, does 
October 20 end, and October 21 begin? 
Fleetwood Vicarage JAMES P£ARSON 
Ocean Meteorological Observations 
I PRESUME that anyone looking at the chart on page 43 of this 
week’s NATURE, or reflecting on the circumstances under which 
barometric observations at sea are ordinarily taken, will agree 
with me that it would be wiser to give only two places of deci- 
mals, and not indicate a degree of refinement which the observa- _ 
tions do not warrant. This point being granted (and even if it 
is not I shall maintain the same line of argument), I submit that 
the writer of the article is in error in saying on page 44: ‘* Range 
corrections for pressure and temperature over the region under 
discussion are not yet accurately enough known to justify the 
committee in ‘correcting’ the results on the large chart by hypo- 
thetical corrections.” 
The daily range of the barometer in the very square under 
notice was investigated under Admiral Fitzroy’s direction, and 
the results were published so long ago as 1861, as the seventh 
number of Meteorological Papers, under the title of ‘‘Inter- 
tropical diurnal range tables of the barometer.’ 
It is very strange if this publication is unknown both to the 
author of the work reviewed and to the reviewer, and yet it is so 
cognate to the subject in hand that there would surely have been 
some reference to it, had they been aware of what had already 
been done. G, J. Symons 
Nov. 25 
Earthquake 
AN earthquake was felt at the Cavendish Bridge Brewery, near 
Derby, on November 13th, at 4h. tom, P.M. J 
Mr. G. T. Eaton, who was in his greenhouse, says ‘‘ the glass 
was very much shaken.” Mrs. Sandford was considerably shaken — 
by a vibratory motion of her chair. Mrs, Eaton’s children, who 
were upstairs, were alarmed. The windows rattled, and the — 
glasses danced on the tables. The sky was dark and threatening, 
with a slight fall of sleet and snow. 
I have delayed sending a report until further evidence could be 
obtained. It is now certain that the shock extended through 
Shardlow; and the earthquake was also felt in the neighbourhood 
at Aston, Castle Donington, and more particularly at Chellaston. — 
E. J. Lowe 
Highfield House, Nottingham, Novy. 24 
—_—— * 
The Birth of Chemistry q 
Mr. RopwELt writes :— The Greek name for tin, ‘kassiteros’? _ 
(karotrepos), was perhaps derived from the Insulse Cassiterides — 
or Scilly Islands ;” but he does not state how these islands came 
by such a high-sounding name. 
I have heard that the root word is Sanscrit, and was known ~ 
in India before the Phoenicians discovered Britain. A. H, 
