224 
NATURE 
[JANUARY 3, 1907 
reasonable explanation of why the a@ particle ceases to 
produce ionising and other effects at a stage when it 
possesses a much greater amount of energy than that 
which is known to be required by a positive ion to produce 
other ions by collision. These effects would cease when the 
uncharged particle was no longer able to become ionised 
by colliding with a neutral atom. The energy (about 
10-" ergs) which it then possessed would represent the 
minimum energy which an uncharged particle must possess 
in order to shake out an electron on collision with a neutral 
atom. 
Even if these speculations are ultimately disproved by 
the facts, it is interesting to note that, with such a con- 
stitution for the a ray, the experiments would measure the 
velocity correctly, whereas the mass, and therefore the 
kinetic energy, would be erroneous to the extent indicated. 
Princeton; N.J:, U.S.A. O. W. RicHarpson. 
The Effect of Radium on the Strength of Threads. 
We have carried out some experiments with cotton 
threads in continuation of those described by Miss Martin 
and one of us in Nature of August 17, 1905. The follow- 
ing is a summary of the’results obtained :— 
No difference in the effect was found when the emanation 
was continuously removed during the exposure by a current 
of air. The same negative result followed an experiment 
in which it was sought to remove oxygen and moisture 
from the neighbourhood of the threads by enclosing radium 
and threads along with phosphoric anhydride in a tube 
from which the air was exhausted, some metallic sodium 
being afterwards heated to fusion in a side tube. 
When threads or a piece of filter paper, after exposure 
to radium, are dyed with methylene blue, the exposed part 
is found to take a deeper colour than the rest. This is 
given as a test for the presence of oxycellulose. 
A series of three-day exposures was made at increasing 
distances from the radium. The effect was found to be- 
come inappreciable at 18 mm. distance. When the weaken- 
ing produced was plotted against distance, the curve showed 
4 corner at 9 mm., suggesting the similar feature found 
by Prof. Bragg and others on the ionisation curves of 
a rays to mark the end of the effective range of one set 
of rays. 
A comparison under the microscope of the broken ends 
of exposed and unexposed threads showed that the fibres 
in the former case were straight up to their ends, while 
the unexposed fibres were curled back on themselves. This 
would indicate a loss of elastic quality through the action 
of the radium. J. L. McKee. 
W. B.+Morton. 
Queen’s College, Belfast, December 27, 1906. 
The Upheaval of the Sea Coast by Earthquakes. 
THE question so long discussed by geologists concerning 
the upheaval of the land by earthquakes has been impres- 
sively revived by recent events. In the San Francisco 
Argonaut of November 3, 1906, Prof. H. D. Curtis, of 
the D. O. Mills Expedition of the Lick Observatory at 
Santiago, Chile, reports that the harbour at Valparaiso is 
now 10 feet shallower than before the earthquake of 
August 16, 1906, and he concludes that the movement was 
mainly vertical. In the Bulletin of the Geological Society 
of America for May, 1906, Messrs. Tarr and Martin give a 
memoir on the changes of level at Yakutat Bay, Alaska, 
produced by the great earthquake of September 3-20, 1899, 
two of the most terrible shocks of which occurred on 
September 1o and 15. ‘The investigators prove conclusively 
that an uplift occurred extending along the whole Yakutat 
coast for more than a hundred miles, the maximum move- 
ment in Disenchantment Bay being 47 feet 4 inches. Up- 
lifts of 7 feet to 20 feet were common, while slight sub- 
sidences also occurred in a few places. 
In view of these facts, how can anyone claim that the 
earth is entirely solid and deny the vertical movement of 
the land under earthquake forces, as is done by Prof. Suess 
in his great work on ‘‘ The Face of the Earth ’’? 
Ws Ma Ao Siar 
U.S. Naval Observatory, Mare Island, California, 
December 8, 1906. 
NO. 1940, VOL. 75 | 
Tue observations of Messrs. Tarr and Martin in Yakutat 
Bay undoubtedly form a valuable addition to the knowledge 
We possess respecting sudden adjustments in the earth’s 
crust. 
In September, 1899, a portion of the west coast of 
Alaska was shattered. Fault lines were created or ex- 
tended, and the displacements along these lines have been 
measured. On January 31, 1906, off the coast of Columbia, 
and on April 18 of the same year in Central California, 
rock movements similar to those at Yakutat were recorded. 
Every world-shaking earthquake—and there are about sixty 
of these per year—is an announcement of a molar move- 
ment. We do not know the magnitude of the masses in- 
volyed, but from measurements like those made by Messrs. 
Tarr and Martin we may estimate them as “being repre- 
sented by one or two million cubic miles of rocky ie 
Emerald Green Sky Colour. 
Tue account of the colour of the sky on December 10, 
1906, sent by your correspondent from St. Moritz closely 
resembles an experience of a friend and myself on 
December 27. 
We were returning from a geological ramble to the west 
of Crediton, in Devonshire, and were walking eastward, 
while behind us and gradually overtaking us there had 
been for several hours a thick snowstorm which later on 
was to envelop us. Between three and four o’clock in the 
afternoon we remarked the peculiar appearance of the 
sky; in your correspondent’s phrase, there was “‘ instead 
of the usual blue, a fairly large expanse of vivid emerald 
green.’’ I may add that the ground was everywhere white 
from previous snow. 
It will be seen that the conditions in Devonshire on 
December 27 correspond as regards time of day, point of 
compass, and state of atmosphere with those observed at 
St. Moritz on December ro. 
With J. W. Noble I shall await with much interest the 
explanation. F. G. Coriins. 
Exeter, 
Perception of Relief by Monocular Vision. 
Tue following fact seems to show that the aperture of 
the pupil plays an important part in the perception of 
relief by monocular vision. 
When a polyhedron made of wire is looked at through 
a small pin-hole pierced on a piece of card, and the pin- 
hole is moved about slightly, the polyhedron seems to 
rotate a little about an axis perpendicular to the direction 
of motion of the pin-hole. The effect is most remarkable 
by lamplight, when the pupil is more dilated than it is in 
broad daylight. T. TeRapa. 
Science College, Imperial University, Tokyo, 
November 15. 
THE GEOLOGY OF THE GERMAN 
ANTARCTIC EXPEDITION. 
HE most striking geographical achievement of the 
German Antarctic Expedition was its determin- 
ation that Antarctica occurs farther north in western 
Wilkes Land than had been inferred by some authori- 
ties from the work of the Challenger. Prof. von 
Drygalski and his comrades have re-established faith 
in Willxes’s Termination Land; as from their Kaiser 
Wilhelm Land they saw high land to the north-east, 
only about one hundred miles from the site assigned 
by Wilkes to his Termination Land. The most fully 
investigated locality in the newly discovered Kaiser 
Wilhelm’s Land is the Gaussberg, a basalt mountain 
on the southern shore of the bay in which the Gauss 
reached its farthest south. 
1 ‘Deutsche Siidpolar-Expedition, 1901-1903.” Edited by Erich von 
Drygalski. II. Band, Kartographie, Geologie, Heft i. Pp. 87, 1 map, 
8 plates. (1) E. von Drygalski: Der Gaussberg, seine Kartierung und seine 
Formen. (2) E. Philippi: Geologische Beschreibung des Gaussberges. 
(3) R. Reinisch: Petrographische Beschreibung der Gaussberg-Gesteine. 
(Berlin: G. Reimer, 1906.) Price 18 marks. 
