Skip to main content

Full text of "Seismological Notes"

See other formats



[April 27, 1905 

less truncated as the verge is reached, and bearing little 
evidence of attrition (Fig. 2). Mr. Molyneux is of 
opinion that the cutting back of the falls is due to 
the perpetual hammering action of the vast bodies of 
water falling into, and down upon, the cracks between 
the basalt columns, assisted by tne constant vibration of 
the rock from the precipitated masses of water, and that 
by this constantly exerted force the columns are rent 
asunder and fall into the chasm, taking with them huge 
and deep flakes of the precipice. At low water heaps of 
these blocks, as yet angular and unreduced, may be seen 
in the shallower ends of the chasm. 

Such is one phase of the erosion of the falls. Another 
power is at work below the water line. The blocks that 

water, such parts as are protected by islands must be free 
from such erosion. To-day there are three important 
islands on the lip of the chasm, and more than fourteen 
large ones in 4 miles of river above the falls. In the 
channels between, there must be more prolonged submission 
to moving currents, by which the cataracts at the ends 
of the chasm are being deepened into sloping by-washes. 

The falls have checked the deepening of the Upper 
Zambezi, and until they chisel the groove of the Grand 
Canon back to the western edge of the basalt sheet, the 
upper reaches must continue to run at a high altitude and 
amid low-lying hills. This has prevented the Zambezi 
becoming a navigable river throughout, and has also had 
a marked influence on the geography of South Africa. 

Photo, by Pedrotii, Bulawayo. 

Fig. 2. —View of Victoria Falls seen through the jaws of the Gorge. Danger Point on the left; the promontory of the “knife edge" on the right. 

From the Geographical Journal. 

fall into the chasm disappear in the deeper waters at the 
jaws of the gorge—yet, impelled by the rush of the current 
in the confined walls, they must be grinding down and 
perpetually deepening the canon, to emerge at the eastern 
end as rounded pebbles and form the shingle beds of the 
middle reaches. 

The extraordinary zig-zags or acute angles in the 
canon have always aroused comment, and the author 
thinks that two main causes are responsible for them— 
the position of islands that probably studded the river (as 
now) and also the existence of master joints and fissures 
in the basalt. On Boaruka Island this action is ex¬ 
emplified in a striking manner, for a stream can be seen 
falling down a crevice, that forms, peculiarly enough, 
another acute angle with the chasm. 

Granted that the falls are due to the action of moving 

NO. 1852, VOL. 71] 


HE attraction of the moon has always been felt by 
earthquake workers, whatever may be its effect on 
earthquakes themselves. The latest contributions to this 
aspect of seismology are two papers in No. iS of the 
; Publications of the Earthquake Investigation Committee 
in Japan. Prof. Omori deals with the lunar daily dis- 
1 tribution, finding maxima of frequency between oh. and 
j 5h., and again between i2h. and 13I1., reckoning from 
' the upper culmination. Dr. Imamura, dealing with the 
; synodic monthly variation in frequency, finds that this 
! shows an increase at the syzygies and quadratures; the 
! former is attributed to the combined effects of the attrac- 
■ tion of the sun and the moon, while the latter is explained 
. by the fact that the time of high water at Tokio then 
i coincides with that of the diurnal maximum of barometric 

© 1905 Nature Publishing Group 

A I'RIL 27 , I905] 



pressure. In spite of the ingenuity of this explanation, its 
validity seems doubtful, for the stresses involved can at 
most be only a subsidiary cause of earthquakes, and con¬ 
sequently any effect due to them would naturally be looked 
for at the time when they vary most rapidly in amount 
rather than at that of their maximum. 

The same publication contains a paper, of some im¬ 
portance in this connection, on daily periodic changes of 
level in artesian wells, by K. Honda. It is the account 
of a record, obtained by a self-registering instrument, of 
the daily changes in level of two artesian wells, 380 metres 
and 300 metres depth, in Tokio and Yokohama. Each 
of them showed a periodic change of level which is 
directly correlated with the tides in the neighbouring sea, 
and also a variation due to changes in barometric pressure, 
of such amount as to show that one-third of the changes 
in the first case, and one-fourth in the second, are absorbed 
by the rocks overlying the water-bearing stratum. 

The catalogue of earthquakes felt in Austria during the 
year 1903, forming No. 26 of the Mitteilungen of the 
Austrian Earthquake Commission, is the last of the series 
which will be published under the auspices of the Academy 
of Sciences. In the introduction to the catalogue it is 
announced that from the beginning of 1904 the task of 
collecting and publishing the records of all earthquakes, 
whether of local or distant origin, observed in Austria, was 
taken over by the Zentralanstalt fur Meteorologie und 
Geodynamik. The Earthquake Commission, having pub¬ 
lished the earthquake registers up to the end of 1903, will 
in future confine itself to the encouragement and "publi¬ 
cation of purely scientific investigations. 

After the collapse of the campanile of St. Mark’s, in 
1902, there was a popular demand, inspired by the idea 
that the detonation was likely to precipitate the destruc¬ 
tion of other historic buildings in Venice, for the cessation 
of the usual mid-day gun. The idea was, of course, un¬ 
founded, but to allay the alarm Prof. Vicentini was re¬ 
quested to instal one of his microseismographs, and his 
report has now' been published. The instrument was 
attached to the wall of the ducal palace which faces the 
lagoon and is directly exposed to the sound waves of the 
cannon ; it indicated a vertical displacement, in conse¬ 
quence of the report, of 0012 mm. to 0014 mm., and 
a horizontal displacement of 0-007 mm. to 0 012 mm., being 
about one-half of those produced by a person jumping on 
the floor of the room in which the instrument was in¬ 
stalled, and one-fifteenth of the displacement caused by 
a high wind. From these figures it is evident that the 
sound waves of a cannon can have no appreciable effect 
on a building, though plaster may be detached where this 
has become loosened and separated from the wall by an 
air space. 



Royal Society, February 23. —“ The Colour-physiology of 
the Higher Crustacea,” Part iii. By F. Keeble and Dr. 
F. W. Gamble, Communicated by Prof. Sydney J. Hick¬ 
son, F.R.S. 

(1) The chromatophores of Hippolyte and Crangon are 
multicellular structures. Their branches show differenti¬ 
ation into a firmer ectoplasm and a more fluid mobile 
endoplasm in which the pigment occurs. (2) The form¬ 
ation of the pigments in the larval and post-larval chro¬ 
matophores is described. (3) In addition to pigments, fat, 
in the form of colourless globules, occurs in the chromato¬ 
phores of Hippolyte. This fat lies in special cells of the 
chromatophore, and exhibits a mobility similar to that of 
the pigments of the chromatophore. (4) If fed and kept 
in the dark, or if starved and kept in the light, Hippolvte 
loses little of its chromatophoric fat. Depletion of "fat 
occurs, however, in starved, dark-kept animals. These, 
when exposed to sunlight for five or six hours, show fat 
in their chromatophores. These results show that the 
colourless chromatophoric fat is a reserve food material, 
and point to the conclusion that in the accumulation of 
this reserve fat light plays an important part. (5) At the 
time of settling on the weeds of the sea-shore, Hippolyte 
various is a colourless or faintly brown-striped animal. 

NO. 1852, VOL. 71] 

At this stage it is extremely sensitive to the light con¬ 
ditions of its environment, assuming the colour of its 
surroundings within twenty-four hours. If the environ¬ 
ment be changed, sympathetic change of colour takes place 
in three days. Half- and full-grown Hippolyte are less 
susceptible. With them sympathetic colour-change occupies 
a week or more. 

March 30.—“ On the Distribution of Velocity in a 
Viscous Fluid over the Cross-section of a Pipe, and on the 
Action at the Critical Velocity.” By J. Morrow. Com¬ 
municated by Prof. H. S. Hele-Shaw, F.R.S. 

Summary and Conclusion. —(1) The experiments provide 
a partial confirmation of the theoretically obtained law of 
velocity distribution, but show that this distribution can 
only be obtained under very special conditions, of which 
absolute freedom from obstructions and end effects are 
important; and hence (2) When the flow is direct and 
stream-lines exist, the velocity distribution is not necessarily 
exactly that which may be described as characteristic of 
"normal” flow. (3) At the critical velocity the irrota- 
tional straight line motion ceases and is followed by one 
in which the paths of the particles of fluid are eddying 
and turbulent. The law of distribution of mean linear 
velocity parallel to the axis simultaneously changes from 
the parabolic (or approximately parabolic) to that typical 
of eddying motion. (4) The critical velocity in question 
(being that at which eddying motion ceases" to be trans¬ 
formed into direct motion, and not that at which a highly 
unstable stream-line motion is suddenly disturbed) is not 
accompanied by a sudden change in the velocity parallel 
to the axis at any point in the cross-section. On the 
other hand, as the total flux increases, the experiments 
show a gradual transition from one state to the other, 
due to the change which has occurred in the law of 
velocity distribution. (5) The observations have little bear¬ 
ing on the upper limit of stream-line flow, as observed 
by colour bands. They indicate, however, that the un¬ 
stable direct motion w'ould follow' an approximately para¬ 
bolic law of velocity distribution (as represented by the 
equation obtained for stream-line motion), and that at the 
higher critical velocity this distribution would suddenly 
change to that represented by the equation given for eddy¬ 
ing motion. In this case, then, instead of a gradual 
change of velocity, there would actually be sudden and 
large changes in the velocity parallel to the axis at different 
points in the cross-section of the pipe. (6) The “ Pitot 
law” (v—*/2gh) is at least approximately true at ex¬ 
ceedingly low velocities. 

April 6.—“ The Influence of Cobra-venom on the Proteid 
Metabolism.” By Dr, J. Scott. Communicated by Sir 
Thomas R. Fraser, F.R.S. 

Conclusions. —(1) Practically no change in rate of proteid 
metabolism was induced by the administration of cobra- 
venom, in spite of well marked local reaction. (2) A slight 
decrease in the proportion of urea nitrogen, quite insignifi¬ 
cant compared with that produced' by diphtheria toxin and 
various drugs, was observed. (3) A slight rise in the pro¬ 
portion of ammonia nitrogen occurred. (4) There was a 
slight rise in the proportion of nitrogen in purin bodies. 
(5) The nitrogen in other compounds showed no constant 
change. ( 6 ) The ISO, excreted showed no constant change, 
but in two experiments there was a slight rise. The change 
produced in the proteid metabolism is, therefore, small, 
and such as it is, being in the directions of decreased 
elaboration of urea and increase in the proportion of 
nitrogen excreted as ammonia, it seems to indicate a slight 
toxic action on the hepatic metabolism rather than a 
general action on the proteid changes, and tends to con¬ 
firm the view that the poison acts chiefly upon the nervous 

Entomological Society, April 5.—Mr. F. Menifield, 
president, in the chair.—Specimens of a melanic Grammo- 
ptera, discovered by Mr. J. C. T. Poole at Enfield, and 
apparently quite distinct from any member of the genus 
taken in Britain : 11. St. J. Donisthor-pe. Mr. Gahan, 
to whom the species had been referred, considered it to 
be a form of G. ruficornis .—A specimen of Megalopus 
melipoma , Bates, an insect which so much resembles a 
bee that Bates had said they were indistinguishable in 

© 1905 Nature Publishing Group