242 
NATURE 
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historical verification, he thinks only of an apparent shortening of 
the year, forgetting the month, which, as it has turned out, has 
proved the tell-tale. Least of all can he have imagined that the 
question could be answered, or even asked—What becomes of 
the lost velocity? 
But he says expressly that it is probably the tidal influence of 
the earth that has brought the moon to face the earth constantly 
as it does. Mr. Tait, in the passage from which I have quoted, 
treats this suggestion as originally Helmholtz’s, though, speak- 
ing under correction, I should have said it formed part of 
Laplace’s explanation. Be this as it may, Kant published it 
when Laplace was five years old. 
The essay was reprinted by Nicolovius in his collection of 
Kant's minor pieces. I do not know the date of this publica- 
tion, but 1839 is the date of Roseakranz and Schubert. Yet we 
have Arago in his latest work, and Herschel at least as late as 
1851, affirming the invariable length of the day, not merely as 
approximately established by history, but (internal disturbance 
apart) as a direct result of dynamical principles. It is not 
“general publicity ” that was wanting in Kant’s case, but special 
publicity, the publicity of Transactions and Jahrbiicher. It is 
to be hoped that those who work in the several departments 
of knowledge are now learning to know better what their neigh- 
bours are about. 
Hadley, Middlesex, Jan, 21 C. J. Monro 
Pollen-eaters 
IT AM sorry that Iam unable to give Mr. Bennett all the in- 
formation that he desires, as I have never studied the classifica- 
tion of the Diptera, and do not know the species of the flies in 
question ; nor do I like to trust my memory as to those of the 
flowers. The common dandelion is, however, I think, an espe- 
cial favourite ; and it is evident that in this and other Compositz 
the movements of any insect among the flowrets must scatter 
some of the pollen upon the stigmas, and some may even be 
carried on its legs and body in its wanderings from flower to 
flower, though the smooth body and cleanly habits of the fly 
must be rather an obstacle tothis. But to some other species of 
flowers, on the pollen of which I have sometimes seen them 
feeding, and paid particular attention to this point, I think it 
very doubtful whether their visits can be anything but injurious, 
W. E. Harr 
P.S.—Allow me to correct a misprint in my former note, By 
the substitution of an ‘‘ N” for the initial ‘*h,” the expressive 
popular name of “‘hoverers,” which I used in writing of the 
Syrphide, has been rendered quite meaningless. I should also 
be glad to know whether I am correct in the use of the word 
** mandibula,” in the same note. 
Meteors in South Pacific 
WHILE some natives of these islands were preparing my boat 
for a journey during the night of October 27-28, they were con- 
siderably alarmed by the appearance of a very large meteor. As 
far as I could ascertain from them it became visible near to ¢ 
Ceti, and rushed towards the south-east, leaving a bright train in 
its wake. One of the natives described it as being as large as a 
man’s head ; the others thought it was larger than that. These 
statements about size must be taken with caution, but from the 
excitement it caused I believe the meteor was a very large one. 
It was seen a little before local midnight. 
I was travelling the same night from midnight to 3 A.M., and 
during that time I observed eleven meteors: two of which 
appeared near to Pollux, and disappeared near to 2 Hydre. 
The other nine all appeared near to 7 Canis majoris and pro- 
ceeded through the constellation Argo Navis. The last I saw, 
at 3 A.M., reached nearly to the Southern Cross, which was then 
just above the horizon. ~ 
Only one of the eleven meteors I saw was at all remark- 
able for size, and that was about as bright as Sirius, with which 
I compared it. This was the only one which left any percep- 
tible train. 
I should add that, although Samoa is in the Western hemi- 
sphere, our local time is that of the Eastern hemisphere ; hence 
the dates given are twenty-four hours ahead of the true time of 
our geographical position. S. J. WHITMEE 
Samoa, South Pacific, Oct, 30, 1872 
Aurora Spectra, nts 
-Mr. Capron’s notice of my observations with regard to the 
auroral spectra compels me to say a few words with regard to 
them which I should rather have deferred till I could confirm. 
my suspicions by fresh experiments, The spectrum which. 
appears to coincide with the aurora, is not the ordinary spectrum 
of oxygen obtained by the disruptive discharge, but is, I have 
little doubt, that described by Willner (Phil. Mag. p. 420, vol. 
xxxvii.) It is not uncommon in ordinary /umiére tubes, but I ob- 
tained it with a feeble discharge in tubes filled with electrolytic 
oxygen, and therefore put it down to that gas. It is now two 
years since I made these experiments. Circumstances compelled 
me to leave the research incomplete, and I have hitherto been 
unable to return to it; but greater experience in the difficulties 
of spectrum work has suggested sources of error which I did not — 
then suspect, and I should not feel any surprise if the spectrum 
in question turned out to be that of some carbon compound from 
the india rubber connections. It certainly has a strong family 
likeness to these, and if it were so, would confirm Prof. Piazzi 
Smyth’s coinciience with citron acetylene. I will endeavour 
shortly to decide this. 
As to instrumental power, the greatest I have used on the 
aurora has been that of a 60° bisulphide prism; but this is 
sufficient to show in both lines a breadth distinctly greater than 
the slit. Unfortunately, however, as I think I have hefore 
stated, the auroral line appears equally nebulous on both sides, 
while that in the tube spectrum is shaded mainly towards the 
red. On the other hand it is fair to note that this ceases to be 
visible when the light is faint and the dispersive power not 
greater than that employed on the aurora. 
North Shields, Jan. 18 HEnryY R, PROCTER 
—— . 
On the Words ‘‘ Diathermanous,” ‘‘ Diathermancy,” etc. 
In reply to the question of Mr. W. M. Williams in the post- 
script to his letter (NATURE, vol, vii. p. 202) I beg leave to 
make a few observations, I presume that the author of the 
above terms thought that the idea of the permeability of a medium 
by radiant heat could be better expressed by derivatives of the 
verb @cpyatyw (I heat) than by those of the more elementary 
words @epuos (hot) or @épun (heat). To the former of these 
classes ‘‘diathermanous,” ‘‘diathermancy” (from @epuavots), 
and “ diathermacy”’ (from @epyacla), all belong, though they are 
not very regularly formed, as our English termination ‘*ey” 
corresponds to the Latin “a, as “clemency ” from clementia, or 
the Greek ‘‘7eia,” as “ policy,” from moAtréia. ‘* Diathermous ” 
belongs to the latter class. A 
According to precedents the substantive corresponding to 
“diathermous” might be “ diathermy,” as bigamous, bigamy, 
or ‘‘diathermeity,” as diaphanous, diaphaneity, or ‘‘ diather- 
mosity,” as porous, porosity, but not ‘‘diathermacy,” in which 
the toxin letter ‘‘a” clearly points out its derivation from the 
verb, 
In point of form the words of Latin origin, ‘ transcalent,” 
‘*transcalency,” which have been used in the same sense, are 
quite unobjectionable, and have the great advantage of corre- 
sponding in form with “transparent,” ‘‘ transparency,” ‘* trans- 
lucent,” “translucency,” so that the words expressing permea- 
bility by the rays of light and heat are of similar form, though 
perhaps the derivation of ‘‘calescence” from a neuter verb, 
when an active sense is wanted, may be an objection to their 
use. 
» Seeing, therefore, that “diathermous” has no very eligible 
substantive corresponding to it, I submit that the original words 
“‘diathermanous” and ‘‘diathermancy” are most eligible in 
sense and least objectionable in form of the words of Greek 
derivation. Some perhaps, in spite of the above objection, may 
prefer the Latin words. D 
Dr. Sanderson’s Experiments 
May I ask Dr. Burdon Sanderson to kindly state in your 
columns one or two matters relating to the cheese employed by 
Dr. Bastian in the experiments at which he assisted. He justly 
remarks on the value of a knowledge of methods of demon- 
strating important facts—and I would therefore ask for the 
advantage of other readers as well as my own—some further 
information. I have already to thank Dr. Bastian for stating the 
specific gravity of his turnip-solution, in reply to my request. 
; 1873 . 
es 
