8 NATURE 
[ May 5, 1870 
SIR EDWARD SABINE’S CONVERSAZIONE 
HATEVER may be said by those to whom the 
grapes are sour, the gathering which- met at Bur- 
lington House on April 23 to greet the President of 
the Royal Society, under animating circumstances, 
can hardly fail of beneficial results, whether regarded 
from the social, the moral, or the scientific point of 
view. It would not be easy to devise a happier way of 
bringing novelties at once under practical criticism—of 
making the outliers of science acquainted with the centre, 
of enabling investigators to compare operations and dis- 
cuss facts and speculations, and of giving occasion for re- 
newal of intercourse and removal of misunderstandings. 
As usual, the range of articles exhibited was wide enough 
to include different branches of science, from astronomy to 
natural history, and from electro-magnetism to physiology, 
with achievements of fine art, and of arts mechanical. In an 
exhausted hydrogen tube placed across the poles of an elec- 
tro-magnet, Mr. C.F. Varley produced a beautiful luminous 
arc, the dimensions of which he could vary at pleasure bya 
change in the size of the negative pole, and occasion a 
change of direction by a slight elevation of one end of 
the tube. 
Spectroscopy, as we have more than once had occasion 
to record, owes much to the constructive skill of Mr. 
Browning. We shall return, on a future occasion, to his 
new automatic spectroscope. 
Mr. C. W. Siemens’s Electrical Resistance Pyrometer 
well maintains the reputation of the inventor for applica- 
tion of philosophical principles to mechanical uses. It is 
the very salamander of pyrometers, and will measure 
the temperature of the most highly heated fiery furnace ; 
which must render it indispensable in operations where 
intense heat is required, and to all experimentalists who 
know the imperfections of the pyrometer in ordinary use. 
The construction of the new instrument is based on the 
physical fact that the resistance of pure metals to the 
electric current increases with increase of temperature in 
a simple absolute ratio. A platinum wire of known re- 
sistance is coiled upon a small cylinder of fireclay, and is 
covered by a tube of the same metal, which protects the 
wire from the destructive action of flame, without pre- 
venting access of heat. Thus constructed, the pyrometer 
is placed in the furnace, and is connected by wires with a 
Daniell’s battery of two cells, and with a compact Resist- 
ance-measurer, specially devised by Mr. Siemens, on 
which the observer makes observations at his ease. As 
the fire burns, the electrical resistance of the platinum 
coil rapidly increases, communicates its progress to the 
measurer on which the indications of temperature may be 
read off as entirely trustworthy, even up to the melting 
point of platinum. The importance of such an instru- 
ment as this cannot fail to be recognised by practical 
men, whether among natural philosophers or workers in 
the pyrotechnic arts ; and, for our part, we cordially wel- 
come this new pyrometer as a logical sequence from the 
inventor of the regenerative gas-furnace with its fierce 
heat-producing capabilities. 
Mr. Jerry Barrett, who relieves his hours at the easel 
with natural philosophy, exhibited an auxiliary air-pump, 
which appears to produce that essential desideratum, a 
perfect Torricellian vacuum, To an ordinary air-pump he 
attaches an air-chamber or reservoir, and, communicating 
therewith, two cylindrical glass vessels charged with 
mercury, and connected by a V tube, On working the 
pump the pressure of the air in the lower vessels compels 
the mercury to rise and fill the upper one, in which an 
ingeniously contrived platinum valve plays an important 
part. By continuing the process of filling and emptying 
(the details of which are not easy to describe), the desired 
vacuum is eventually obtained, and the exhausted tube on 
the top of the pump is ready for experiment. We learn 
that a well-known experimentalist was so favourably im- 
pressed by the capabilities of this pump that he intends to 
have anumber of large tubes made for a series of experi- 
ments. 
Inthese days of busy telegraphy, Mr. J. Parnell’s new 
secondary battery is worth attention. It isso constructed 
as to be capable of alarge amount of heavy work, having 
forty cells, each containing a pair of copper plates immersed 
in a solution of the impure carbonate of sodium, known in 
commerce as “soda.” By this employment of an alkali, 
the electromotive force produced is supposed to depend on 
the electrolytic reduction of the sodium. The battery is 
arranged inten compound cells of four couples each, and 
ischarged by a small battery of five Grove cells, and afterthe 
connection has been established for a few seconds, a com- 
mutator of peculiar construction is brought into play, and 
excites the whole forty cells to activity. It is thought 
that a battery so constructed, which can be energised at 
pleasure by a brief communication with the small Grove, 
will be found of service in telegraphing through lines of 
great resistance. 
Rear-Admiral Inglefield’s contrivance for making the 
water in which a ship floats do the work of steering 
appeals to every Englishman, for are we not all interested 
in our navy, whether Royal or commercial? It is a con- 
trivance which involves a large economy, for instead of a 
number of men labouring at two wheels, and with 
relieving tackles, it requires one small wheel only, and 
one man to steer the largest ship afloat ; estimating 
roughly the pressure of the water as half a pouna per 
square inch for every foot of the ship’s draught. Ad- 
miral Inglefield admits the water through the bottom by 
a “Kingston valve” into a cylinder placed at the stern. 
The piston of this cylinder works a double-action force- 
pump, which sends the water to two hydraulic cylinders ; 
these are connected with a tiller four feet in length, and 
thus, by movements of the small steering wheel, the ship 
is easily steered. Trials made with this apparatus on 
board the Achilles, one of the largest vessels in the 
navy, proved satisfactory ; and in an improved form it is 
to be fitted to the Fethz Bulend,a corvette now building for 
the Turkish Government. Unfortunately for the visitors to 
the conversazione, the model exhibited, owing to lateness of 
delivery, could not be shown in work; but there was a 
skeleton of the corvette’s stern, showing the position of 
the apparatus, and near it stood one of the small steering- 
wheels, By this and Admiral Ingletield’s explanations, the 
naval men present could form an opinion of the new 
method, compare it with the existing method, and 
mark how surely the helm could be kept hard over 
during full speed, and how rapid and easy were its 
movements generally. 
Mr. J. B. Rogers exhibited his life-saving apparatus, by 
which he has obtained the prize long offered by the Ship- 
wrecked Mariners’ Society, and furnished means of rescue, 
which, judging from the trials made near Portsmouth 
under authority of the Admiralty, are likely to render 
valuable service. With a mortar and a small charge of 
powder he throws out an anchor from the shore, and by 
means of the double rope thereto attached, a lifeboat can 
be hauled out through a heavy surf in weather when it 
would be impossible to launch her in the usual way ; and 
with the further advantage that the hauling need not be 
done by the crew of the boat, who would consequently be 
fresh for their laborious task of rowing out to the ship in 
distress. 
The Meteorological Office of the Board of Trade in 
carrying out their scheme of “ ocean statistics,” from which 
great advantage may be anticipated to navigation and to 
meteorological science, have constructed two charts, the 
value of which all whose business it is to go down to 
the sea in ships will appreciate. The wind chart is the 
first instalment of a series intended to show the best 
route for crossing the line in each month of the year. To 
facilitate reference, it is ruled in squares each represent- 
ing a degree, with the direction and force of the prevailing 
