592 
NALORE 
[ApRIL 22, 1897 
OUR ASTRONOMICAL COLUMN. 
REFRACTION AND THE APPARBNT DIURNAL MOVEMENTS 
or STars.—The question of the apparent change of positions 
of stars due to refraction as the hour angle varies, becomes of 
importance when long intervals of time are taken into account. 
In photographing the stars, it is generally usual to ‘stand by” 
and make all the necessary small adjustments, due to atmo- 
spheric refraction, with the hand. A method has, however, been 
recently suggested and worked out by Dr. A. A. Rambaut, by which 
the rate of the driving clock may be so adjusted as to take into 
account these minor discrepancies when a high state of accuracy 
is desired for stars at large hour angles (J/os¢hly Notices, vol. 
Ivii. No. 2). This method does not, of course, take into con- 
sideration local or temporary changes in the refraction, but the 
perfectly regular and systematic change as the star increases or 
decreases its altitude. For a telescope to follow a star with 
absolute precision, a clockwork must be constructed which 
would drive the instrument at an ever-varying rate according 
to the formula given by Dr. Rambaut. This, however, can- 
not be practically achieved, and would, further, be unnecessary, 
as a close approximation is all that is needed in practice. By a 
system of curves obtained from the above-mentioned formula, 
and treated graphically, it has been found that a uniform rate, 
if suitably chosen, will not in ten minutes introduce an error 
amounting to one-twentieth of a second, which is within the 
limits of the accidental errors of a good equatorial clock. By 
prolonging the exposure beyond the period for which a uniferm 
rate is admissible, the rate must be altered to one now more 
suitable. A series of weights, skilfully employed in controlling 
the action of a pendulum in connection with the driving clock, 
will allow the different rates to be easily produced. Dr. 
Rambaut describes a graphical method for obtaining the length of 
exposure during which a uniform rate may be used. This he finds 
most convenient in practice for short exposures, and he relates 
that he can turn his telescope, with the greatest confidence, from 
a star at its upper culmination, to follow which a star must lose 
at the rate of from 18 to roo seconds or more a day, and one at 
its lower culmination, gaining atthe rate of 70 or So seconds 
a day, and he finds *‘ the telescope will follow both with equal 
accuracy.’’ It may be remarked that this method is practically 
iniended to be utilised when photographs for the detection of 
stellar parallax are in question, as it is only then that they must 
be obtained when the stars have a considerable hour angle. 
““ BULLETIN ASTRONOMIQUE DE FRANCE.’ —The April num- 
ber of this monthly contains, among other things, an interesting 
article, by Camille Flammarion, on the planet Venus, more 
special attention being paid to the observations which have indi- 
cated the presence of anatmosphere. There is also an account of 
Mr. Percival Lowell’s recent observations on the surface mark- 
ings, and the subsequent determination,of the period of rotation, 
mentioned previously in this column. 4 fropos of our note last 
week, on the question of the adoption of France of Greenwich 
time,.we find that the following resolution was voted by the 
assembly at the meeting of the french Astronomical Society, on 
March 3 last, the proceedings of which are here recorded :— 
“*La Société astronomique de France, considérant qu’au Congrés 
de Washington la proposition du méridien de Behring, qui avait 
un caractere eminemment géographique, impersonnel et d’ordre 
universel, n’a pas été adoptée, ne juge pas a propos d’en adopter 
un autre, qui n’a a aucun degré le caractére auquel la France 
est toujours restee fidele dans les réformes dont elle a pris 
Vinitiative.”” This number of the Azé/etiz contains also several 
communications 1elating to the moon, and another beautiful 
reproduction from one of Loewy and Puiseux’s lunar negatives is 
given, which, for amount of detail and fine contrast, is strikingly 
beautiful. 
Pror. EpuARD HaERDTL.—The Professor of Astronomy at 
Innsbruck, Prof. Eduard Freiherr von Haerdtl, whose death 
(Astr. Nach., No. 3416) we regret to record, was born in the 
year 1861 at Penzing, near Vienna. After finishing his Gym- 
nasium studies in 1880, he selected mathematics and astronomy 
as his chief pursuits at the Vienna University. He was one of 
the most apt pupils of Th. von Oppolzer, whose work he 
vigorously took up, and afterwards so ably continued. In 1892 
Haerdtl was promoted to the Professorship of the Innsbruck 
University. Endowed with a great capacity for carrying out 
astronomical computations, his dissertation ‘‘ Beitrage zur 
Assyrischen Chronologie ” was followed by other publications, 
NO. 1434, VOL. 55] 
chief of which was the investigation of the movement of Win- 
necke’s comet. The prize of the Copenhagen Academy of 
Sciences he won with an interesting essay, entitled “‘Skizzen zu 
einem speciellen Fall des Problems der drei Korper,” after 
which he busied himself with the terms of long period in the 
movement of the moon, and shortly before his death with 
Winnecke’s comet again. Full of such promise, and cut off at 
the early age of thirty-six, not only has astronomical science 
lost a man who seemed destined to enrich her with many 
valuable contributions, but his circle of friends mourn the loss 
of a kind and true ‘* Kamerad.” 
ON ELECTRICAL PROPERTIES OF FUMES: 
PROCEEDING FROM FLAMES AND BURN- 
ING CHARCOAL} 
§1. MARY experimenters have investigated the electrical 
4 properties of flames and incandescent solids. The 
methods usually employed have been (1) to examine the electric 
conductivity of different parts of the flame; (2) to measure 
the difference of potential between platinum wires in different 
positions in the same flame ;* (3) to find the leakage of a charged 
conductor when placed near, or in view of, a flame or an 
incandescent solid ; 4 (4) to observe the leakage of a conductor, 
raised to a red or white heat, by an electric current, and elec- 
trically charged while it is surrounded by different gases ; °-and 
(5) to observe the production of electrification or diselectrifica- 
tion by a glowing wire, through which a current is passing; 
in neighbouring insulated conductors separated from it by 
different gases." 
§ 2. This short communication divides itself into three sep- 
arate inquiries: (1) to test by one of our electric filters’ the 
electric quality of the fumes from different flames and burnings. 
(this method has not, we believe, been tried before) ; (2) to 
observe the difference of potential between a copper plate and 
a zinc plate when the fumes from different flames and burnings. 
at different distances from the plates passed between them and 
round them; and (3) to observe the leakage between two 
parallel metal plates with any difference of electric potential 
when the fumes from flames and burnings were allowed to pass 
between them. 
§ 3. To test the electrification of fumes from different flames 
and burnings, the arrangement shown diagrammatically in Fig. 1 
was used. The flame is kept burning at the mouth of a large 
vertical iron funnel a, closed at its upper end; and the heated 
air, along with the products of combustion, is drawn off by am 
air-pump through a small aperture, B, near the upper end. 
Before reaching the pump the air has to pass through three 
circular pieces of brass wire gauze, D, one centimetre apart, 
which are fixed across the funnel about 5 centimetres below the 
exit tube B; and through a worm of block-tin pipe, 90 centi- 
metres long, which is kept surrounded by cold water in a vessel 
c. The electrification was tested by a quadrant electrometer 
(sensitiveness of the electrometer 111 scale divisions per volt), 
and an electric filter F. ‘he filter F was of block-tin tube, 5. 
centimetres long and 1 centimetre bore, and full of fine brass 
filings kept in position by a plug of cotton-wool and a piece of 
brass wire gauze at each end. Between the filter and the air- 
pump is a T-shaped piece of glass tubing with lower end of 
the vertical tube dipping into a basin of mercury. This served 
as a pressure gauge to indicate the difference of air pressures 
on the two sides of the filter when the air-pump was worked. ° 
The flame, the iron funnel, the worm, and the case of the 
electrometer are all metallically connected. 
1 By the Right Hon. Lord Kelvin, G.C.V.O., F.R.S., and Dr. Magnus. 
Maclean. Paper read ata meeting of the Royal Society, Edinburgh, on 
April 5. 
= Account of experiments in Wiedemann’s ‘‘ Lehre von der Elektricetat,” 
vol. iv. B. Carl's Ref., xvii. pp. 269-294, 1881. J. J. Thomson, P/zé.. 
Mag., pp. 358, 441, 1890. r 
* Hankel, Phil. Wag., p. 542, December 1851 ; Phil. Mag., p. 9, January 
1860. Elster and Geitel, Wed. dun., vol. xvi., 1882; also Phil. Mag., 
September 1882. Maclean and Goto, PAr/. Mag., August 1890. 
4 Guthrie, Pi7l. Mag., p. 308, April 1873. Giese, red. Ann., vol. xvii. 
Schuster, Lecture Royal Institution, February 22, 1895. 
_ > Guthrie, Piz. Mag., p. 237, October 1873. 
6 Elster and Geitel, Wied. Ann., xxxvii. p. 315, 1889; Elster and Geitel, 
Wied. Ann., xxxviii. p. 27,.1889. . 
7 Kelvin, Maclean, Galt, ‘‘ Electrification and Diselectrification of Air,” 
Proceedings of the Royal Society; London, vel. lvii., February and March 
1805 ; also B.A. Report. 1895. 
