JuLy 10, 1902] 
NATURE 
259) 
Many astronomers will regret the necessity for the inclusion 
of the following paragraph in the report, for it announces a 
great loss to observational astronomy generally, and especially 
to that of the southern hemisphere :— ‘‘In consequence of the 
author’s advancing years, it is probable that there will bea 
considerable relaxation in his efforts for the year 1902.” 
EXTENSION OF THE KATHODE RADIATION HYPOTHESIS TO 
NeEBUL«&®.—At the meeting of the Académie des Sciences held 
on June 23, M. Janssen presented a note from M. Deslandres, in 
which the latter extends the kathode ray hypothesis, which he 
had already proposed in order to explain solar phenomena, to 
nebule. 
The author says that the hypothesis of Arrhenius which 
attributes the light emitted by nebulz to electrified particles, 
and also that of Nordman which attributes it to Hertzian rays 
gathered from space, are both wrong, for if they were true, the 
terrestrial atmosphere itself would, at night-time, display 
similar light; therefore, he adds, the light must be in the 
nebulz themselves. 
PERSONAL EQUATION IN THE MEASUREMENT OF SPECTRO- 
scopic NEGATIVES —In a note to the Memorie della Societa 
degli Sp-ttroscopiste Italiani, M. Hasselberg makes some 
interesting statements on the part that the personal equation 
of the observer plays in the measurement of photographic 
spectra. (uoting the note on this subject, by Mr. Reese, in 
The Lick Observatory Bulletin, No. 15, wherein it was demon- 
strated that the tendency in the case of Mr. Reese was to place 
the dark lines of the spectrum negative, as contrasted with the 
bright lines, a little too much to the right of the field of the 
microscope, M. Hasselberg goes on to demonstrate that in 
his own case the tendency is exactly opposite. Consequently, 
he finds that, in general, his personal equation makes his wave- 
lengths come out systematically less than those published by 
Rowland for the same lines. 
The author gives three sets of measurements of metallic 
spectra which he has observed, compares them with the analo- 
gous values obtained by Rowland, and, after meaning the 
differences to eliminate accidental errors, he finds that there 
remains a systematic difference of +0°007 Angstrém units, and 
this he ascribes to purely physiological causes. 
In the third table given by M. Hasselberg he compares his 
measurements of the lines in the tungsten spectrum : (1) when 
the lines are brought to the centre of the field from the left to 
the right, and (2) when they are brought to the centre from the 
right to the left, and here he finds that in the first case his 
values are too great, whilst in the second case they are too 
small. 
The author concludes by pointing out that, although these 
errors are very small, yet they are too pronounced to be neg- 
lected, and shows that by a curious coincidence his personal 
error would, if introduced into the determination of radial 
velocities, produce a difference of exactly 1 kilometre per 
second from the true velocity. 
APPARENT DEFORMATIONS OF THE SUNS 
DISC NEAR THE HORIZON. 
ALTHOUGH curious deformations of the apparent shape of 
the sun and moon near the horizon have been noticed from 
the earliest times, observations are not very frequently made, 
and the apparent changes of the appearances of these bodies 
when near the horizon cannot be said to be very commonly 
known. Among the earliest descriptions of this phenomenon 
may be mentioned one during ‘‘ The strange and dangerous 
voyage of Captaine Thomas James, in his intended Discovery 
of the Northwest Passage into the South Sea,” London, 1633. 
He states :—‘‘ I obserued the Sunne to rise like an Ouall, alongst 
the Horizon: I cald three or foure to see it, the better to 
confirme my Judgement: and we all agreed, that it was twice 
as long as it was broad.” On March 26, 1632, James obs-rved 
the same phenomenon at the time of the rising of the moon. 
Biot, in his ‘‘Traité élémentaire d’Astronomie physique,” 
writes :—‘‘ C’est encore par un effet de la réfraction atmo- 
sphérique que le Soleil 4 horizon parait ovale et aplati dans le 
sens vertical, méme dans les temps les plus calmes et les plus 
sereins. Tous les points de son disque sont alors élevés par 
Veffet de la réfraction, mais ils le sont inégalement : les points 
inférieurs le sont plus que les supérieurs, parce qu’jls sont plus 
prés de l’horizon, ow la réfraction est plus forte. te disque du 
Soleil doit donc alors sembler aplati, dans le sens vertical. ” 
NO. 1706, VOL. 66] 
Among more recent papers upon this phenomenon may be 
mentioned one by Lieut. F. Krifka, entitled, ‘‘ Refractions- 
erscheinungen der aufgehenden Sonne” (AZefeorologische Zett- 
schrift, 1891, p. 101). During the trigonometrical survey of 
Brno in Bohemia, Colonel von Sterneck directed attention to the 
remarkable shape of the rising sun, and careful observations 
were taken by himself with a telescope, and by Lieut. KyYifka 
with the naked eye, until the sun rose above the horizon. 
Illustrations are given of the shape and colour of the sun during 
fifteen phases ; the colour was first a deep red and gradually 
faded into yellow as the sun regained its globular appearance. 
The forms were very curious, some resembling a basin with a 
projecting lid ; others appeared very much like the shape of a 
mushroom, with its stalk ; Jater, an oval shape was assumed. 
Fic. r. 
Duming the voyage of the Belgian Antarctic ship Be/gica, 
M. H. Arctowski, a member of the scientific staff, made frequent 
observations of the phenomenon in question between Rio de Ia 
Plata and the Straits of Magellan, both when the sun was rising 
and setting, and he has communicated the results in an interest- 
ing paper published in the Budletiz de la Société belge 
d’Astronomie, accompanied by outline sketches. The descrip- 
tion given of the phenomenon seen on November 23, 1897 (Fig. 
1), off the coast of Patagonia is typical of other observations. On 
approaching the horizon the lower portion of the sun became 
flattened, and continued to become more deformed as it 
descended. At about 3° above the horizon there was a thin 
film of cloud, and the part of the sun which was still above the 
level of this little cloud preserved its regular shape. Gradually 
the lower part assumed a triangular shape, a little point or 
stem appeared, and became enlarged as it touched the horizon. 
The sketches show that all the zone comprised between the fine 
belt of cloud and the horizon possessed the property of deforming 
the sun’s disc, and that in every case the cloud was the principal 
seat of the deformations. After the sun had set it was scarcely 
possible to see the cloud. The sketches very closely resemble 
the Bohemian illustrations already mentioned. 
The accompanying figure (Fig. 2) isa reproduction of a photo- 
graph showing deformation of the setting sun, taken by Prof. W. 
Prinz, of the Royal Observatory of Belgium, at Uccle, near 
Brussels, and communicated to the Memorie della Soczeta degli 
Spettroscopisti italiani, by Prof. A. Riccd. The dark back- 
ground is drawn exactly circular, in order that the defor- 
mation of the sun’s disc may be seen more clearly. In this 
case the ratio of the vertical to the horizontal diameter is 
75:84 mm. = 0°893. 
