Fuly 1, 1886] 
NATURE 
alan 
lutely fixed, if it is solar it oscillates with the lever.— 
On a hyperbolagraph, by Mr. H. H. Cunnynghame. It is not 
an unfrequent want to be able to find a rectangle of greatest or 
least area contained between a curve ani reciangular co- 
ordinate axes. In several problems connected with motion and 
pressure in steam-engines this is useful, and even in political 
economy the graphic representation of monopoly curves depends 
on maxima and minima of this nature. For the solution of such 
problems it is often very useful to be able to describe rectangular 
hypertolas, and the author has devised a machine to effect this. 
It depends on a mathematical property of the rectangular hyper- 
bola, which he believes to be new, and which is as follows: 
From a fixed point let any line be drawn to meet a fixed line, 
and from the point of meeting draw the line perpendicular to the 
fixed line, and equal in length tothe first line. The locus of the 
extremity of the second line is a rectangular hyperbola, or if 
from a fixed point O a line OP be drawn to meet a fixed 
line in a point P, and PQ be taken perpendicular to the 
fixed line, so that OP + OQ be constant, then again the 
locus of Q is a rectangular hyperbola. In the machine the 
latter construction is mechanically and continuously carried out. 
A pencil, whose point corresponds in position to the point Q, 
slides along a rule which is carried across the paper always per- 
pendicularly to the fixed line. A fine steel wire attached to the 
pencil passes over round a roller at P, and is then carried to and 
coiled round a similar one at O. The use of a steel wire is a 
special feature of the apparatus, and has a great advantage over 
string, which, owing to the facility with which it stretches, can- 
not give good results. The finest wire should be used: it 
unrolls f-om the one roller as much as it laps over the other, 
and its use may be extended to nearly all curve-drawing 
machines.—A voltaic cell with a solid electrolyte was ex- 
hibited by Mr. Shelford Bidwell. Its construction is as fol- 
lows: upon a plate of copper is spread a layer of quite dry 
precipitated sulphide of copper; if on this a clean plate of 
silver is placed, and the cell joined up to a galvanometer, a 
slight deflection is observed due to the unavoidable presence of 
moisture. If, however, the silver plate be covered with a slight 
film of sulpbide of silver, by pouring on it a solution of sulphur 
in bisulphide of carbon and evaporating the free sulphur by 
heat, and then placed with the prepared side down as before, a 
deflection is obtained far greater than, and in the opposite direc- 
tion to, the former. The resistance of the cell was very great, 
but was enormously reduced by compression; the E.M.F. was 
about ‘07 volt. 
Mineralogical Society, May 21.—Prof. M. F. Heddle, 
M.D., F.R.S.E., in the chair.—The following papers were 
read:—On the nomenclature of the hydrocarbon compounds, 
with a suggestion of a new classification, by Andrew Taylor, 
F.C.S.—On new localities for diatomite, by Prof. W. Ivison 
Macadam.—On new localities for the mineral agalmatolite, with 
notes on its composition, by W. Hamilton Bell.—On a new 
locality for agalmatolite, with analysis, by Prof. W. Ivison 
Macadam.—The metallic ores of Chilé, by John F. Kerr, illus- 
trated by a splendid collection of specimens.—On the chemical 
composition of the mineral found by Mr, Wallace at Loch 
Bhruithaich, Ross-shire, by Prof. W. Ivison Macadam.—Note 
on serpentine from Creag Mhor Thollie, Loch Maree, by Prof. 
W. Ivison Macadam.—Notice of mica trap from Farley, near 
Beauly, by T. D. Wallace.—An excursion was made in the 
afternoon to the Spindle and Buddo Rocks, under the guidance 
of Prof. Heddle. 
EDINBURGH 
Royal Society, June 21.—Sheriff Forbes Irvine, Vice-Presi- 
dent, in the chair.—Mr. Omond, of Ben Nevis Observatory, 
read a paper on the diurnal variation in the direction of the 
summer winds on Ben Nevis. These varying winds seem to be 
entirely local, and are caused by the heating of the one side of the 
mountain by the sun, while the other is cooled by radiation. 
The air consequently passes over the mountain from the hot to 
the cold side.—Mr. A. Buchan read a paper on the meteorology 
of Ben Nevis. He referred chiefly to three points :—(1) tem- 
perature-variation ; (2) variation of barometric pressure; (3) 
wind-speed. As regards temperature, there is the usual morning 
minimum and afternoon maximum, which tend to be obliterated 
in the winter months. ‘The barometer reads below average in 
the early morning, and above average in the afternoon. There 
is an afternoon minimum, which tends to disappear in summer. 
The wind-speed is below average during the night, and above 
average in the afternoon. The barometer reads low when the- 
wind is high at the top of the mountain. Mr. Buchan pointed 
out that the great advantage of the Observatory is that simulta- 
neous observations are made at the top of the mountain and at 
the foot, the station at the foot being on an incline sloping 
down to sea-level. If this latter condition is not satisfied, no 
reliance can be placed upon deductions from the results obtained 
as to the rate of diminution of temperature with height. The 
Observatory at Hong Kong is so conditioned, and the rate of 
diminution, as deduced from results obtained there, is 1° F. per 
281 feet. From the Ben Nevis observations Mr. Buchan finds it 
to be 1° F. per 270 feet.—Mr. G. W. W. Barclay described some 
algoid lake-balls found in South Uist.—Dr. W. Hunter read a 
paper on the duration of life of the red blood-corpuscles, as 
ascertained by transfusion. Three weeks is the average period 
given by his experiments. When there is no devitalising action 
in the corpuscles by the method of observation employed, it is 
probably from three to four weeks. 
PARIS 
Academy of Sciences, June 21.—M. Jurien de la Graviere, 
President, in the chair.—lmprovement of the bar at the mouth 
of the Senegal River, by M. Bouquet de la Grye. Having 
studied the question on the spot during the year 1885, the author 
proposes some simple measures by which the dangerous effects 
ofthe bar might be obviated and the navigation of the Senegal 
waters greatly improved.—On some double phosphates of 
thorium and potassium or of zirconium and potassium, by MM. 
L. Troost and L. Ouvrard. By preparing a certain number of 
phosphates of thorium and the corresponding compounds of zir- 
conium by the dry process, the authors have endeavoured to- 
verify the analogy pointed out by several observers between 
thorine and zircon. They find that the metaphosphate and the 
pyrophosphate of potassa yield with thorine and zircon double 
phosphates which have analogous compositions, but are not iso- 
morphous. The orthophosphate of potassa gives double phos- 
phates which have different compositions ; nor is there any iso- 
morphism between thorine and zircon obtained by calcination 
of the double phosphates at very high temperatures.—On the 
ammonia present in the ground, by MM. Berthelot and André. 
In reply to M. Schleesing’s last paper the authors claim to have 
made good their original statement that the ammonia present in 
the ground should be analysed without any dessication or 
previous treatment. They also join issue on various incidental 
points raised by M. Schloesing himself during the controversy. — 
On the extension to a class of analogous forms of the theorem 
relative to a number of asyzygetic invariants of a given type, by 
Prof. Sylvester.—On the discovery of a new metal, austrium, 
announced by M. Ed. Linnemann in the Monatshefte fiir Chemie 
for April 1886, by M. Lecoq de Boisbauiran. From the de- 
scription given of its chemical properties, its electric spectrum, 
and the proces of its extraction from the orthite of Arendal, the 
author thinks that this substance is very probably gallium, a 
small quantity of which might easily be contained in orthite. 
The two rays of austrium approximately measured by M 
Linnemann are A = 403'0 and 416°5, those of gallium being 
403°2 and 417'05. For both the ray 417 is the strongest.— 
Remarks accompanying the presentation of three volumes of the 
Annales du Bureau central météorologique fcr 1884, by M. Mas- 
cart. Attention is drawn especially to M. Fron’s paper on the dis-- 
tribution of thunderstorms in France during the year 1883; to 
M. Moureaux’ memoirs on the methods employed at the Parc 
Saint Maur Observatory for the study of terrestrial magnetism ; 
and to M. Teisserenc de Bort’s paper on the distribution of 
cloudiness over the surface of the globe.—Observations of 
Brooks’s Comet III. (c, 1886), made at the Observatory of 
Algiers (0’50m. telescope), by M. Ch. Trépied.—Developments: 
in trigonometrical series of certain functions verifying the equa- 
tion of the potential AF =o, by M. Appell —Note on some 
new groups of surfaces of two dimensions in spaces of 7-dimen- 
sions, by M. Giovanni Bordiga.—Observations on M. Ledieu’s 
note relative to the roll of vessels at sea, by M. de Bussy.—On 
the vapours emitted by a mixture of volatile substances, by 
M. P. Duhem. It is shown that the partial pressure of the 
vapour emitted by each of the two fluids mixed together is less 
than the tension of saturated vapour of the same fluid taken in 
the pure state. —Dynamics of the molecule of water: velocity of 
the propagation of sound ; compressibility ; heat of fusion of ice ; 
specific heat of ice, by M. M. Langlois.—Calorimetric study of 
iron at high temperatures, by M. Pionchon. A detailed exami- 
