160 
NATURE 
[ DECEMBER 17, 1903 
OUR ASTRONOMICAL COLUMN. 
Tue Torat Soar Eciirse or May, 1900.—The report of 
the expedition organised by a joint committee of the Royal 
Dublin Society and the Royal Irish Academy to observe 
the total solar eclipse of May, 1900, has just been published 
in vol. viii. (series ii.) of the Scientific Transactions of the 
Reyal Dublin Society. 
The instruments used were chiefly lent by Sir Howard 
Grubb and Mr. W. E. Wilson, F.R.S., who, with Prof. 
Joly, Dr. A. A. Rambaut and others, were members of 
the expedition. They included two ccelostats and two 
coronagraphs, one of the latter being of 4 inches aperture 
and 19 feet 4 inches focal length, the other of 6 inches aper- 
ture and 7 feet 103 inches focal length; a special spectro- 
scopic apparatus for securing a continuous series of photo- 
graphs of the spectrum of the chromosphere was also taken. 
The second of the two coronagraphs was used with a 
coloured screen, made by ‘‘ fixing’? an ordinary unexposed 
film, and then soaking it in a bath of tartrazine, which 
allowed only the green light about the chief coronal 
radiation to be photographed. The resulting negative, 
which was exposed for eighty seconds, shows considerable 
extension of the outer corona, although the spectroscopic 
observations indicated that the green corona line was very 
faint during this eclipse. ; 
The spectra were obtained with a kinematograph 
especially designed by Sir Howard Grubb to take twelve 
plates at the second and twelve at the third contact, in such 
a manner that no interval occurred between two successive 
exposures, the idea being to observe whether all the bright 
lines appeared or disappeared simultaneously, or whether 
some became reversed earlier than others as would be ex- 
pected if their respective absorptions took place at different 
levels. It was found that the lines generally disappeared 
in the order of brightness shown on the original spectrum, 
although there were several exceptions to this rule, notably 
the strontium lines at A 4078 and A 4216, which disappeared 
earlier than other lines of the same original intensity. These 
differences are shown in the analytical table which accom- 
panies Dr. Rambaut’s discussion of the spectra. The wave- 
lengths and origins given in this table seem less determinate 
than those which have been previously published by other 
observers. Several plates showing reproductions of the 
corona photographs, which have been discussed by Mr. 
Wesley, and of the spectra are given at the end of the 
paper. 
CLoups ox Mars.—An 
; article by Mr. Denni i 
in the December number ofa een pu plished 
1 of the Bulletin de la Société astro- 
nomique de France, records the appearance op. eleucalilee 
formations on Mars during the latter half of May. On May 
19 and 21 the Syrtis Major was dark and sharply defined 
but on the latter date a brilliant region appeared over its 
southern extremity, whilst on May 23 this region was very 
faint and ill-defined, although other features usually less 
obvious were plainly seen. Mr. Denning describes the 
region as appearing to be covered by strongly reflectin 
vapours which were not dense enough to hide com fetal 
the surface, but were sufficiently dense to give it A z 
luminous and less definite appearance, On May 25 and 27 
a luminous zone was observed to the north of the Mare 
Cimmerium, and during the latter part of the month = 
extensive luminous band was visible along the northern edge 
of this sea, Syrtis Major, and the Linus Sabzeus. It ere 
probable to Mr. Denning that the clouds of white vapour 
which were observed on the eastern edge, south of Syrtis 
Major, on May 21 travelled very rapidly in a northern direc- 
tion, and thus caused the lack of definition observed in the 
above regions On the later dates, and he connects this 
phenomenon with the appearance of a white projection 
observed by Mr. Lowell, at Flagstaff, on May 26. ; 
_Several other remarkable phenomena, notably a marked 
division of Nilus by a bright spot, which extended far to 
the south-east from the eastern edge of the Lunze Lacus, on 
May 4, Were observed by Mr. Denning, and, on analysin 
his observations, he arrives at the ‘conclusion that va 
changes do present themselves in the details of several 
Martian features, although many of them may be only 
temporary and due to atmospheric causes. ; 
As regards the question of Martian canals, Mr. 
NO. 1781, VOL. 69] 
a more 
Denning 
states that there is no doubt as to the objective reality of 
the streaked and striated appearance of the northern hemi- 
sphere, and to him the canals appear not as straight and 
narrow lines, but as currents of dark material with frequent 
condensations having the appearance of a natural rather 
than an artificial origin. 
SEISMOLOGICAL NOTES. 
THE fourteenth number of the Publications in European 
languages issued by the Earthquake Investigation 
Committee of Japan is entirely devoted to a profusely illus- 
trated paper on the modulus of rigidity of rocks, by Mr. S. 
Kusakabe. The experiments, which are a continuation of 
investigations made by Prof. H. Nagaoka on the elastic 
constants of rocks, relate entirely to torsion, and show, 
amongst other things, that even for very small strains 
Hooke’s law does not hold, that in the relationship of 
stress to strain, or twisting couple to twist produced, rocks 
exhibit a marked hysteresis, and that the modulus of 
rigidity of a rock in its virgin state is greater than is usually 
supposed. Inferences to be drawn from these important 
investigations (in which stresses are applied slowly) are 
that waves of small amplitude are propagated with 
a higher speed than those with a large amplitude 
(increase an amplitude ten times and the velocity is 
reduced to half or one-third), also in a strained medium, 
as, for example, along a mountain chain, velocity is some- 
what increased. In view of the first of these inferences, 
Mr. Kusakabe does not see the necessity to assume that the ° 
tremors of an earthquake follow paths different from that of 
the large waves or shocks. Whether we agree or disagree 
with this suggestion, we can congratulate the author on 
his important memoir, which is a new leaf in seismo- 
metrical research. 
Amongst other recent publications relating to earthquakes 
we have before us Nos. 13 and 14 of the new series of Mitteil- 
ungen issued by the commission appointed by the Vienna 
Academy of Sciences for seismological investigations. 
The first of these, by Dr. R. Hoernes, gives an account 
of the earthquake which, on July 5, 1902, resulted in con- 
siderable destruction along a line to the east of Saloniki, 
and fairly parallel with the Vardar River. This is a fault 
line along which there are hot and other springs. From 
the fact that these became muddy, altered in temperature 
and in volume, whilst new springs were created, as at 
Guvezne, the inference is that the earthquake was accom- 
panied by subterranean rearrangements of strata. A dis- 
cussion of the movements along this and other fault lines 
in Macedonia, and of changes in level which are apparently 
in progress at Saloniki and its neighbourhood, leads to the 
conclusion that hypogenic geological processes have in this. 
part of the world a marked activity. 
The second communication, from Prof. Dr. W. Laska, is 
on the determination of the distance of earthquake origins 
from observing stations by means of seismograms. ‘That 
the differences in time between the arrival of various phases. 
of earthquake motion vary with the distance an earth- 
quake has travelled is a fact which has received application 
for many years. In the reports of the Seismological Investi- 
gation Committee of the British Association (1900 and 1902), 
by means of curves the relationship between the time 
intervals and distances is expressed geometrically. Dr- 
I.4ska gives similar information by means of tables. From 
observations made at three stations he also gives equations 
the solution of which leads to the determination of a lati- 
tude and longitude for an epicentrum. In the British 
Association report for 1900 simpler and more certain solu- 
tions are given for the same problem. 
In No. 15 of the same Publications Dr. Eduard Mazelle 
gives the results of his investigations respecting the con- 
nection between microseismical pendulum movements, the 
wind, barometric pressure, the state of the ocean, and other 
natural phenomena. The results at which the author 
arrives confirm the results from similar analyses made many 
years ago in Japan, and to be found in the Transactions of 
the Seismological Society of that country and in the reports 
of the British Association. We are told that it is difficult to 
find a direct connection between tremors and atmospheric 
