Aug. 25, 1870] 
NATURE 
341 
by the hydro-pneumatic gun-carriage has been sketched, 
it is evident that all the applications of the principle of 
utilising the recoil as embodied in this engine have not 
been exhausted. The force of the recoil which must be 
exhausted in bringing the gun down to the loading posi- 
tion is very much greater than the force that would be 
required simply to raise the gun again to the firing posi- 
tion. The recoil takes place very rapidly, much more 
rapidly than it is desirable that the gun should rise again. 
If in the Protected Barbette Carriage it was allowed to re- 
turn freely to its firing position, it would come up with an 
inconvenient or even a dangerous violence. The super- 
fluous energy of the recoil stored up in the counter-weight 
must, therefore, be controlled and exhausted by friction 
bands. Inthe hydro-pneumatic carriage the return of the 
gun can be completely controlled by the valve or stop- 
cock G, so as to bring it to the loading position as 
gently as desired, and the superfluous energy of the recoil 
will take the form of heat developed in the compressed 
air of the reservoir. But this superfluous energy may be 
seized and utilised. If a second and smaller plunger is 
attached to the cross head of the main plunger, which 
supports the gun and its carriage, with a cylinder and 
reservoir of its own, the power there accumulated may be 
used for any other purpose, as training the gun and car- 
riage. In this case also, though the pressure produced 
and the heat generated in the main reservoir will not be 
so great as if there was no second plunger, still it alone 
will contain an ample store of force to bring the gun again 
into its firing position. 
To discuss the military advantage of this invention, as 
a substitute on board ships of war for a turret weighing 
300 tons of wrought iron, affording more complete protec- 
tion to gun and gunners, and not weighing for a twenty- 
five ton gun more than sixteen tons altogether, would be 
travelling out of the realm of NATURE, 
We have only endeavoured to show in this example 
with how great efficiency and docility Nature obeys those 
who understand how to direct her forces, and that all her 
work is not only efficient but instructive. If we can per- 
suade her to undertake a new task she will teach us a new 
lesson. In the hydro-pneumatic gun-carriage a means 
supplies itself for measuring the exact amount of work 
done by the recoil. The compression of the air in the 
reservoir, and the heat generated in the process, will give 
accurate data for measuring the force exerted, and by this 
a step will be made towards measurements of the power of 
explosives with a precision hitherto unattainable. 
Nature, like the great ancient fabulist,if she is compelled 
to be our slave, is resolved also to be our teacher, 
NOTES 
THERE is one part which neutrals may take in the Continental 
war. With no sympathy for those who have caused the war on 
either side, our sympathy is all the more due to those who inno- 
cently suffer from it on both sides. The following appeal, posted 
on the walls of every maérze in France, will touch other hearts than 
those of Frenchmen :—‘“‘ Appel 2 la France.—Au nom de Dieu, 
au nom de la patrie, au nom de nos fils, de nos fréres, de nos 
brayes soldats tombes avec honneur sur le champ de bataille, et 
toujours héroiques quoique vaincus aujourd’hui, nous faisons un 
appel & tous les ceeurs frangais. De grace, donnez-nous de 
Yargent, du linge, des chemises, des couvertures, des vétements, 
de flanelle, etc, La-bas, sur nos frontiéres, l’élan des villes, les 
offrandes touchantes des villages ne suffisent déja plus 4 nos chers 
blessés.—Les besoins sont immenses.—Le temps presse.— 
Donnez, oh! donnez vite! Envoyez les dons en nature et en 
argent au siége de la société 4 Paris, Palais de Industrie, porte 
No. IV.” Here is a work in which all may unite—French, 
Germans, and neutrals, men of science, men of literature, men of 
business; and above all, our women. Nobly already have Eng- 
lish, Irish, and Americans, surgeons, nurses, sisters of charity, 
come forward in the good work, butstill it can only be as a‘drop 
in the ocean. To offer succour to the wounded jand sufferers ‘on 
both sides, to assuage as far as we can, the horrors of war, never 
exhibited on a more fearful scale than within the last few weeks, 
is now the duty of our more fortunate countrymen and country- 
women, 
ANOTHER sacrifice of science to the war! The Congress of 
Alpine Geologists, the meeting of which we announced to take 
place on the 31st of this month, is adjourned to a more favourable 
time. It is probable also that the Congress of Anthropology 
and Pre-historic Archeology which it was proposed to hold at 
Bologna, and that of German naturalists to take place at 
Rostock, will not be held. 
Tue following sectional arrangements of the British Associa- 
tion are now announced :—A—MATHEMATICAL AND PHYSICAL 
SCIENCE (in the Crown Court, St. George’s Hall) : President— 
J. Clerk Maxwell, F.R.S. L. and E. ; Seeretaries—Prof. W. G. 
Adams; W. K. Clifford; Prof. G, C. Foster, F.R.S. ; 
Rey. W, Allen Whitworth. B—CHEMICAL SCIENCE (in the 
Royal Institution, Moore Street): President—Prof. Henry E, 
Roscoe, PhD., F.R.S., F.C.S. 3; Secretaries—Prof. A. Crum 
Brown, F,R.S.E., F.C.S.; A. E. Fletcher, F.C.S.; Dr. W. 
J. Russell, F.C.S. C—GroLocy (in the Concert Hall, Lord 
Nelson Street) : President—Sir Philip de Malpas Grey Egerton, 
Bart., M,P., F.R.S., F.G.S.;  Secretaries—W. Pengelly, 
F.R.S., F.G.S.; Rev. H. H. Winwood, F.G.S.; W. Boyd 
Dawkins, F.R.S,, F.G.S.; G. H. Morton, F.G.S. D—BrioLocy 
(in the Reading Room and Lecture Room of the Free Public 
Library): President—Prof, G. Rolleston, M.D., F.R.S., F.L.S. ; 
Vice-Presidents—John Evans, F.R.S., F.G.S,, F.S.A. 5 Prof. 
Michael Foster, M.D., F.L.S. ; Secretaries—Dr. T. S. Cobbold, 
F.R.S., F.L.S. ; Thos. J. Moore; H.T, Stainton, F.R.S., F.L.S., 
F.G.S. ; Rev, H. B. Tristram, LL.D., F.R.S. E—GrocRAPHY 
(in the Small Concert Room, St, George’s Hall): President— 
Sir Roderick I. Murchison, Bart., K.C.B., D,C.L., LL.D., 
F.R.S., F.G.S.; Secretaries—H, W. Bates, Assist. Sec. 
R.G,S, ; Clements R. Markham, F,R.G.S.; Albert J. Mott ; 
J. H. Thomas, F,R.G,S, F—EcoNoMIc SCIENCE AND STA- 
TisTIcs (in the Council Chamber, Town Hall): President— 
Prof. Jevons ; Secretaries—E. Macrory; J. Miles Moss. G— 
MECHANICAL SCIENCE (in the Civil Court, St. George’s 
Hall) : President—Charles Vignoles, C.E,, F.R.S., M.R.LA., 
F.R,A.S. ; Secretaries—P, Le Neve Foster ; J. T. King, 
Tue Dutch Society of Sciences, of Haarlem, instituted last 
year, in addition to its ordinary prizes, two large gold medals, 
each of the value of 500 florins, one of which bears the name 
and effigy of Huyghens, the other of Boerhaave. These medals 
are to be awarded alternately, once in two years, to the savant, 
Dutch or foreigner, who shall haye contributed the most, during 
the previous twenty years, to the progress of one particular 
branch of mathematical physics or of natural science, The 
Huyghens medal is to be devoted in 1874 to chemistry, in 1878 
to astronomy, in 1882 to meteorology, in 1886 to mathematics, 
pure and applied. The Boerhaave medal is to be granted in 
1872 to mineralogy and geology, in 1876 to botany, in 1882 to 
zoology, in 1884 to physiology, in 1888 to anthropology. The 
series will then recur. At their recent annual meeting the 
society made the first award of the Huyghens medal to M. 
Clausius for his discoveries in thermo-dynamics. 
Sir FREDERICK PoLtock, late Chief Baron, whose death is 
announced as haying taken place on Tuesday last, in the 87th 
year of his age, was an amateur photographer of no mean 
ability, and had been President of the London Photographic 
Society ; he was an occasional contributor of articles on photo- 
graphy to the Philosophical Proceedings of the Royal Society. 
