Jory 9, 1914] 
Vries’s hypothesis of twin hybrids from mutating 
species; (11) theory of a differential division in the 
zygote; and (iii) the reaction theory. 
A paper on the vegetation of the Sargasso Sea was 
contributed by Prof. W. G. Farlow, of Harvard Uni- 
versity. The Sargasso Sea is characterised by the 
scattered masses of gulf weed which float on the 
surface of the ocean in patches from 50 to 1oo ft. in 
diameter. Some consider that the gulf weed, Sar- 
gassum bacciferum, is merely a mass of sterile 
branches of some species of Sargassum, which grows 
attached in the region of the West Indies, and truits. 
Others believe that in its present floating form it is 
a distinct species which has lost the power of fruiting 
and increases only by offshoots. In recent years the 
species of Sargassum growing in different parts of the 
West Indies have been studied, and a comparison with 
the floating gulf weed shows that mixed with it are 
found fragments of at least two species known to grow 
in the West Indies. In only one instance has there 
been found mixed with the gulf weed a seaweed which 
must have come, not from the American coast, but 
from Africa or southern Europe. There is reason to 
think that the gulf weed is derived from some Sar- 
gassum growing in the West Indies, fragments of 
which are carried by the Gulf Stream to the Sargasso 
Sea. 
On April 24 a paper on phase changes produced by 
high pressures was read by Mr. P. W. Bridgman, of 
Harvard University. Pressures as high as 30,000 or 
40,000 kgm. per sq. cm. were employed. Examina- 
tion of the melting of a number of liquids over a wide 
pressure range has shown that the theories hitherto 
proposed do not hold at high pressures. So far as 
can be judged the melting curve continues to rise 
indefinitely, so that a liquid may be frozen by the 
application of sufficient pressure, no matter how high 
the temperature. A number of results are also ob- 
tained for the reversible transition from one crystal- 
line form to another. Several new solid forms have 
been obtained; of particular interest are the new forms 
of ice which are denser than water. In addition to 
these changes, which are completely reversible, one 
example has been found of an irreversible reaction 
produced by high pressure; yellow phosphorus may be 
changed by 12,000 kgm. and 200° to a modification 
in appearance like graphite, which is 15 per cent. 
more dense than the densest red phosphorus. 
Prof. R. A. Millikan, of the University of Chicago, 
read a paper on some new tests of quantum theory 
and a direct determination of h. It has been known 
for twenty-five years that when light of sufficiently 
short wave-length fails upon a metal, it has the power 
of ejecting electrons from that metal. It has been 
known for seven years that the kinetic energy 
possessed by the electrons thus ejected is larger the 
higher the frequency of the light which ejects them. 
Whether or not the energy of ejection is directly pro- 
portionate to frequency has been a matter of some 
uncertainty. Prof. Millikan’s work furnishes proof 
that there is exact proportionality between the energy 
of the ejected electrons and the frequency of the light 
which ejects them, and that the factor of proportion- 
ality between the energy of the ejected electrons and 
the frequency of the incident light is the same quantity 
as the fundamental constant which appears in Planck’s 
theory of the discontinuous or explosive character of 
all radiant energy of the electromagnetic type. This 
constant is known as Planck’s h, and its value is 
directly determined with an error which does not 
exceed I per cent. 
Dr. Charles F. Brush, of Cleveland, discussed ‘tA 
Kinetic Theory of Gravitation : (1) Gravitation is Due 
to Intrinsic Energy of the A®ther; (2) Transmission of 
NO. 2332, VOL. 93] 
NATURE 
ao 3 
’ 
Gravitation cannot be Instantaneous.’’ He employs 
illustrations to show that the energy acquired by fail- 
ing bodies has some external source, and that it must 
be etherial energy or energy of space; and he holds 
that the term “ potential energy of position,’’ as applied 
to a system of gravitating bodies, implies the energy- 
endowed ether as a necessary part of the system. As 
a corollary, he explains how bodies falling toward 
each other by reason of their mutual attraction, and 
thus accelerating—that is to say, absorbing energy from 
the wther—cannot rigidly obey Newton’s law of in- 
verse squares of distance. In the second division of 
the paper the premises from which Laplace drew his 
famous conclusion that gravitation is transmitted with 
infinite, or virtually infinite, velocity, are described, a 
dogma which, said Dr. Brush, ‘‘for more than a 
century has blocked the path of fruitful thought on 
the physics of gravitation.’’ It is concluded that, even 
if the velocity of transmission is no. greater than that 
of light, the moon’s mean motion will be retarded a 
very few seconds of are only, in a century; and the 
retardation will be correspondingly less if the velocity 
is greater than that of light. This retardation, of 
course, adds to the unexplained acceleration, if any, 
of the moon’s motion; but the author further hopes 
that this retardation, plus the outstanding accelera- 
tion, will be explained by a particular deviation from 
Newton’s law described. 
Prof. W. Duane, of Harvard University, presented a 
contribution on highly radio-active solutions. The 
advantage in using these solutions in studying the 
effects produced on tissues is that after injection 
the radio-active substances come into intimate contact 
with the tissues, and thus the full power of the alpha 
rays is utilised. If a solution of radium itself is in- 
jected, the process is not only costly, but dangerous, 
on account of the long life of the radium. The solu- 
tions do not have these objections, for the radium is 
not wasted in producing the solutions, and the activity 
lasts for only a short time. If the injection is made 
subcutaneously, a large fraction of the activity remains 
in the neighbourhood of the point of  injec- 
tion, and the rest is carried off in the lymph 
and blood streams. The rapidity with which 
the activity gets into circulation is astonish- 
ing. A drop of blood taken from another part of the 
body only a few seconds after the injection is more 
radio-active than carnotite or pitchblende ores. It 
would seem that this might prove to be a delicate 
method of studying the flow of fluid through the 
tissues. On making tests by means of the gamma 
rays an hour or an hour and a half after the injection 
it was found that there was very little activity in the 
brain and lungs, but that there was a tendency for 
the substances to deposit out in the liver, spleen, and 
kidneys. 
‘“‘The Relations of Isostasy to a Zone of Weakness 
—the Asthenosphere,’’ was the subject of a paper by 
Prof. J. Barrell, of Yale University. The mass of 
every mountain tends to deflect the plumb-line slightly, 
so that the measured latitude and longitude of any 
locality will differ as it is determined by triangulation 
or by astronomic determination of the point in which 
the observed vertical pierces the celestial sphere. But 
Hayford has shown that the deflections of the vertical 
are actually only one-tenth of the deflections calculated 
as due to the terrestrial relief. This is a quantative 
test of the degree of isostasy. Dynamically it implies 
a state of flotation of the crust upon the inner earth 
analogous to the flotation of an iceberg in the ocean. 
Yet the earth as a whole is known to be as rigid as 
steel; the nature of earthquake vibrations transmitted 
through the earth shows it to be solid throughout and 
more incompressible and rigid at great depths than 
near the surface. How, then, shall the geodetic 
