12:2 
NATURE 
[Fune 10, 1886 
very great advantages in its favour; and, for all laboratories 
supplied with aqueduct-pressure, I venture to think that it 
affords the best solution of the problem of inexpensive, con- 
venient, and effective power. Davip P. Topp 
Lawrence Observatory, Amherst, Mass., May 15 
Scientific Nomenclature 
Iw a letter published in Narure for May 27 (p. 76) Prof. 
Minchin proposes to replace the expression ‘‘ potential energy ” 
by ‘‘static energy.” It seems to have escaped his notice that a 
similar expression, proposed many years ago by Sir William 
Thomson, was used until it was replaced by the very words 
which Prof. Minchin wishes now to abolish. A short account 
of the question is given by Maxwell in ‘‘ Matter and Motion,”’ 
p. 81, and I should like to bring the following passage to the 
notice of those who take an interest ia this question :— 
“This is called the ‘sum of the tensions’ by Helmholtz in 
his celebrated memoir on the ‘ Conservation of Energy.’ Thom- 
son called it statical energy ; it has also been called energy of 
position ; but Rankine introduced the term potential energy—a 
very felicitous expression, since it not only signifies the energy 
which the system has not in actual possession but only has the 
power to acquire, but it also indicates its connection with what 
has been called (on other grounds) the potential function.”’ 
Harrow, June 8 G, GRIFFITH 
Nezra 
I WISH to request any of your readers who may dredge, or 
have opportunity this summer, to observe living or fresh speci- 
mens of the genus Meera, Gray, and see whether branchiz exist 
in that group. A Lamellibranch without branchize is anomalous, 
tosay the least. I find in a new species of Meera (sub-genus 
Myonera) from the Gulf of Mexico the following anatomical 
facts :—The mantle closed except for the small siphon and a 
narrow short slit for the thorn-shaped foot ; no gills, no palps ; 
the oral opening circular, plain ; the roof of the peripedal cavity 
between the base of the body and the mantle margin is flattish, 
fleshy, with sparse pustules ; a peripheral very stout pink muscle 
runs on each side around this, and is prolonged upward to the 
shell before the true adductor at each end of each valve, thus 
accounting for the double scars to be found there ; the foot is 
close to the oral orifice, not grooved for the byssus, but pedun- 
culated and surrounded by a groove; around the siphonal 
opening are numerous tentacular processes and a moderate 
number of ocelli. The specimens appear to be adult and per- 
fectly preserved. An examination of specimens of Meera arcti-a 
and Neera olesa, Lovén, indicated a similar state of affairs, 
though these specimens were not in as good condition as the one 
from the Gulf of Mexico. I do not find in the literature any 
categorical statement of the observation of gills in this genus. 
Clark is non-committal (in his ‘‘ British Testacea”’), Jeffreys speaks 
of seeing the ‘pink gills” through the shell, but that which he 
saw fink was without doubt the circular muscle I have men- 
tioned, 
The question is worthy of a definite solution. | My specimens 
seem to leave no doubt that there are no gills, but it is always 
best to be suspicious of material long in alcohol. 
Wm. H. DaLi 
Smithsonian Institution, Washington, D.C., May 27 
“Plants and their Defences” 
WITH regard to the interesting article in your issue for May 6 
(p- 5) on ** Plants and their Defences,” I should like to offer 
two remarks, and in return would be very glad to receive from 
you information upon a certain point. (1) The author enumer- 
ates different species of plants protected by the severe stings of 
ants, but dves not seem to know the remarkable work of Beccari, 
‘*Piante ospitatrici ossia piante formicarie della Malesia e della 
Papuasia” (Malesia, vol. ii., Firenze, 1885). Beccari describes 
seventeen partly new species of ‘‘ Myrmecophilous ” Rubiacez, 
among which are eleyen of Hydzophytum (not Hydvio- 
phytum, as is erroneously given in the article in NATURE). You 
will find a further contribution to this question in Henry O. 
Forbes’s ‘‘ Wanderungen durch den Malayischen Archipel,” 
vol. i. pp. 84-88 of the German translation. 
For my part, I should be greatly obliged if you would com- 
munica‘e to me the title of the original work from which the 
author of ‘‘ Plants and their Defences” has taken his account of 
Triplaris Schomburghiana, Schomburghia tibicinis, andzAcacia 
spharocephala. 
(2) Concerning the same article, Mr. Alfred W. Bennett 
(Nature of May 20, p. 52) is inclined to think that the poison- 
ous fluid of the nettle-glands is not formic acid, as generally 
conjectured, because the fluid frequently has an alkaline reac- 
tion. As a matter of fact, Prof. Dr. Haberlanlt, at Graz 
(Austria), has recently, in vol. xciii. of Swsungidberichte des 
haisrl, Akademie dr Wissenschaften in Wien, 1886, Februar-. 
Heft, shown in his article, ‘‘ Zur Anatomie und Physiologie der 
pflanzlichen Brennhaare,” that (1) the poison of the stinging 
glands is not identical with formic acid ; (2) mor is it the albu- 
men dissolved in the fluid of the glands; but (3) that most 
probably this fluid is a transformed ferment or enzymotic poison. 
Frankfurt a, Oder, June 2 E. Huru 
A Remarkable Hailstorm 
On April 17, at 4 o'clock p.m. (local time), a very remarkable 
hailstorm visited the neighbourhood of asmail hamlet, called 
Et Totumo,' not far from the town of Tinaco, section Cojedes, 
State of Zamora, Venezuela, The place is approximately in 9° 
25 N. lat., and 68° 5’ long. W. of Greenwich, certainly not more 
than 200 metres above sea-level. My informant is a resident of 
El Totumo, named Nicolas Moreno Nunez, who is universally 
said to bea trustworthy and respectable man. There was first a 
very heavy thunderstorm with much rain; but after some time 
hailstones began to fall in such abundance that it might have 
been easy to collect them by hundreds of bushels, some weighing 
as much as two ounces. It is well known that between the 
tropics hailstorms are exceedingly rare in localities situated in 
the lowlands ; but the present case is still more interesting, on 
account of the colour of the hailstones, some of which were 
whitish, whilse others were blue or rose-coloured. I have read of 
but one instance in which the two last-mentioned colours were 
observed, viz. in the hailstorm of Minsk of June 14, 1880, 
described by Lagunowitch, and quoted by Th. Schwedoff in his 
memoir “On the Origin of Hailstorms.”* Schwedoff thinks 
that the blue and rosy colours are owing to the presence of salts 
of cobalt and nickel, and thus confirm his hypothesis of the 
cosmic origin of hail. Ido not know whether the existence of 
those mineral constituents in the hailstones of Minsk was ever 
made certain by chemical analysis, and it is of course impossible 
for me to do so in the present case, when almost a month has 
passed since the phenomenon took place. But it is undoubtedly 
a very curious coincidence that the sae colours should have 
been observed in both instances and in localities so widely 
separated from each other; whilst there is not the slightest 
possibility that my informant, an honest and plain countryman 
of no literary education whatever, should have had any know- 
ledge of such an observation having been made before. 
Caracas University, May 12 A. ERNST 
VISITATION OF THE ROYAL OBSERVATORY 
HE visitation to the Royal Observatory by the Board 
of Visitors took place last Saturday, when there 
was a very numerous attendance. The report of the 
Astronomer-Royal to the Board gives, as usual, an 
account of the work done during the past year, and 
references to any points of interest or importance which 
have been raised. From the report we select the follow- 
ing particulars :— 
Mr. Turner has recently investigated the discordance 
between observations for coincidence of the collimators 
made respectively through the apertures in the cube of 
the transit-circle and with the instrument raised. A 
wooden model of the cube was constructed through which 
the observation could be made when the transit-circle 
was raised, and it was thus shown that the discordance 
was due to the cutting off of portions of the object-glasses. 
by the cube, and not to any effect of tem,erature. In 
view of this result it seems desirable that the optical 
* This is the vernacular name of the calabash-tree (Crescen/ia Cujete) > 
there is, or was, probably a remarkable specimen of this tree in the neigh- 
bourh od of the hamlet. 
_* Lonly knowa Spanish translation of Schwedoff’s memoir, in Crénica 
cienffica (Barcelona), 1882, No. 120, pp. 553-60. 
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