Juuy 9, 1914] 
Inorganic ‘‘ Feeding.’’ 
Ar the January meeting of the Physical Society, 
and also at the recent conversazione of the Royal 
Society, I showed an experiment in which one globule 
oi liquid (dimethyl aniline), floating on the surface 
of water, captures and absorbs other floating globules 
(orthotoluidine), the movements resembling those of 
an amoeba. I have now succeeded in ph_tographing 
the process, and in the accompanying print the larger 
globule is seen in the act of engulfing the smaller 
and darker-coloured one. 
To secure contrast, 
the orthotoluidine was 
coloured with indigo. 
An interesting exten- 
sion of this experiment 
is provided by placing a 
small drop of quinoline 
on the surface after the 
absorption of the ortho- 
toluidine is nearly com- 
plete. This drop ap- 
proaches the large 
globule and makes con- 
tact, when it is violently 
repelled ; it again approaches, and is then repelled with 
less force; and this alternate attraction and repulsion 
continues until the quinoline drop. appears to be 
nibbling at the edge of the large globule, into which 
it is finally absorbed. The interesting feature of this 
process is that at each contact a mutual! interchange 
of liquid occurs; and only when the quinoline has 
become mixed with a considerable quantity of the 
liquid composing the larger globule does absorption 
take place. Cuas. R. Dartinc. 
City and Guilds Technical College, 
Finsbury, E.C. 
EXPERIMENTAL DEMONSTRATION OF AN 
AMPERE MOLECULAR CURRENT IN A 
NEARLY PERFECT CONDUCTOR. 
T has long been known that the electrical re- 
sistance of metals falls with a reduction of 
temperature in an approximately straight line law, 
indicating that, in the neighbourhood of absolute 
zero, there would be no resistance whatever. 
Prof. H. Kamerlingh Onnes, of Leyden, has 
carried experiments on this subject down to ex- 
tremely low temperatures, and has found that 
it is at a point a few degrees above absolute zero 
that the resistance of certain pure metals practi- 
cally vanishes. His later experiments illustrate 
the properties of these almost resistanceless 
‘bodies, or, as he terms them, “super-conductors,” 
in a very striking way. Taking a closed coil of 
lead wire, he cooled it down by immersion in 
liquid helium to a temperature at which its resist- 
ance is of the order of 2x 10-1 that at normal 
temperatures. He then induced a current in the 
coil, which, instead of ceasing with the E.M.F., 
vas shown to persist with scarcely sensible 
diminution for as long a period as the coil could 
be kept cold. As there was practically no resist- 
ance, there was practically no dissipation of 
energy, and the system behaved like the imagined 
molecular currents of Ampére, and realised the 
conception of Maxwell as to a conductor without 
resistance. 
The little coil in question was made of 1,000 
Nees 332, VOL. Gai 
NATURE A81 
turns of lead wire 1/70 mm. diameter, wound 
on a brass bobbin, and with its ends fused to- 
gether. Its resistance at a normal temperature 
was 734 ohms, and it was calculated that the 
induced current would then only persist for 
1/70,000th of a second after removal of the 
E.M.F. When cooled by liquid helium to 1°8° K. 
(abs.) the “relaxation time,” according to previous 
determination of the resistance, should be a matter 
of days. The limiting value to which the current 
might be raised before the ordinary resistance 
suddenly makes its appearance had also been cal- 
culated, and found to be o’8 amperes at 1°8° K. 
The coil was contained in a suitable vessel intro- 
duced between the poles of a large electromagnet, 
which was excited before the liquid helium was 
poured in. After the coil had been cooled down, 
the current was cut off from the magnet and a 
current thus induced. The unexcited magnet was 
then removed, and the persistence of a current of 
about o'6 ampere in the lead coil was demon- 
strated by a magnetometer arrangement. During 
an hour no decrease in the magnetic moment pro- 
duced could be observed, although the tempera- 
ture had risen to 4°26° K. (that of helium boiling 
at atmospheric pressure). When the coil was 
lifted out of the helium the current ceased imme- 
diately as the temperature rose above 6° K., which 
is the “vanishing point ” of the resistance of lead. 
The experiment was repeated with the windings 
of the coil parallel to the field, to prove that the 
effect was not due to some magnetic property of 
the material of the wire or bobbin, which might 
only appear at these temperatures; and only a 
slight effect, such as might be accounted for by 
asymmetry of the coil, was observed. Further 
experiments were tried to measure the actual rate 
of falling off of the current due to the residual 
micro-resistance, and a falling off of less than 
I per cent. per hour (somewhat less than had been 
calculated) was all that could be observed. Other 
experiments finally disposed of all idea of direct 
magnetic action, and the actual presence of a 
continuing current was proved independently by 
attaching galvanometer leads to the points on the 
coil, and suddenly cutting the wire between them 
under the helium, when a swing of the galvano- 
meter needle was observed, while the magneto- 
meter immediately went to zero. 
MEMORIAL STATUE OF CAPT. COOK. 
N Tuesday, July 7, Prince Arthur of Con- 
naught unveiled a statue of Captain Cook, 
which stands on the Mall side of the Admiralty 
Arch, at the end of the Processional Road. The 
proposal to erect the statue was made in 1908 by 
Sir J. H. Carruthers, who pointed out that there 
was no memorial of Captain Cookin London. The 
matter was taken up by the British Empire 
League, and a general committee, under the presi- 
dency of the Rt. Hon. Herbert Samuel, M.P., was 
formed to promote the erection of a statue. The 
necessary funds were raised, and in 1911 Sir T. 
Brock, R.A., was commissioned to execute the 
memorial. One hundred and thirty-five years 
