NovEMBER 29, 1906 | 
NATURE 
105 
Atlantic islands, it arrived back in the Clyde in July, 
1904. 
The narrative of the expedition is told by three 
members of the staff, Mr. R. C. Mossman, the 
meteorologist and magnetic observer; Dr. J. H. H. 
Pirie, the medical officer and geologist; and Mr. 
R. N. Rudmose Brown, the botanist. Each author 
contributes the chapters describing the work with 
which he was most concerned. The book perhaps 
suffers as literature from the difference in treatment 
of successive chapters, but it has the advantage of 
describing the whole expedition by the first-hand 
accounts of men concerned in all the different sections 
of the work. 
The narrative is of great interest. It tells the 
story of long, thoughtful preparation, of the setting 
forth of a band of determined men, each well trained 
in his own line of work, and of their quiet, successful 
achievement of their purpose. The expedition must 
be regarded, especially in view of its low cost, as 
remarkably successful. Its discovery of Coats Land 
Fic. 2.—Penguin rookery on Graptolite Island. 
determined the hitherto quite unknown southern limit 
of the Weddell Sea, and has broken the longest un- 
known line in the coast of Antarctica. As far as can 
be judged from published information, the Scotia will 
probably be found to have contributed more to 
Antaretic oceanography and biology than any of the 
expeditions in the field at the same time. Its deep- 
sea equipment was excellent, and was fully used, and 
the description of the quantities of material obtained 
in the deep-sea hauls justifies the hope that the bio- 
logical collections will yield most important contri- 
butions to our knowledge of the Antarctic fauna. 
J. W. G. 
SYNTONIC WIRELESS TELEGRAPHY. 
@* Tuesday evening, at a reception given by Lord 
Armstrong at the Queen’s Hall, Sir William H. 
Preece, K.C.B., F.R.S., being in the chair, a very 
important and interesting demonstration was given 
by Mr. Valdemar Poulsen before a large audience, 
which included, among others, H.R.H. the Duchess 
of Argyll, the Duke of Argyll, and the Danish Ambas- 
sador, of a new development of wireless telegraphy 
NO, 1935, VOL. 75] 
From ‘‘ The Voyage of the Scofza. 
which affords grounds for hoping that the problem of 
syntonic signalling is at last nearing practical 
solution. 
Mr. Poulsen will be familiar to readers of Narure as 
the inventor of the telegraphone (see Nature, vol. Ixii., 
p- 371, and vol. Ixiv., p. 153). Before describing the 
experiments shown at the Queen’s Hall, it will be advis- 
able to give a short account of the principles on which 
the new method is based. It has often been pointed out 
in Nature that all attempts hitherto made with regard 
to selective signalling are of a very unsatisfactory 
nature, and it has been suggested (NaTuRE, vol. Ixviii., 
p. 249) that the solution is likely to be found in the 
application of the principle discovered by Mr. Duddell 
in the “‘ musical” or ‘‘ singing’? arc. It is precisely 
that principle that Mr. Poulsen has adopted. The 
reason for this is sufficiently clear when it is con- 
sidered that syntony, or tuning between transmitter 
and receiver, means the emission by the transmitter 
of sustained vibrations of definite frequency. Only 
when these are produced is it possible to employ in 
the receiver a circuit tuned or reson- 
ating to this particular frequency. 
The main difficulty with all 
methods of spark transmission is to 
produce these sustained vibrations. 
The signal produced by a spark dis- 
charge consists of a series of violent 
pulses each consisting of a short 
train of strongly damped vibrations 
of definite frequency. Such tuning 
as can be done is accomplished by 
making the natural period of vibra- 
tion of the receiving circuit the 
same as the vibration period of the 
individual pulses, but as the effect 
of the pulse itself as such is prac- 
tically as great as that of its com- 
ponent vibrations, it will be readily 
seen that the tuning is only partial. 
To make the syntonisation effectual, 
the effect of the pulse must be 
diminished and that of the vibra- 
tions increased. In order to do this, 
the damping of the vibrations must 
be lessened until the signal is no 
longer a series of rapidly damped 
waves, but becomes a continuous 
succession of undamped, or, at 
the worst, very slightly damped 
vibrations, and the culminative 
effect of the continuous succession of waves will be 
far greater. 
The problem, therefore, reduces itself to the produc- 
tion of a train of undamped waves, and the manner of 
its solution was indicated by Mr. Duddell when he 
discovered the phenomenon of the singing are 
(Nature, vol. Ixiii., p. 182). Mr. Duddell showed that 
if a continuous current arc, burning under such con- 
ditions that a small rise in the current is attended by 
a small fall of potential—or in symbols for which 
dv/dA is negative and numerically greater than the 
resistance of the shunt circuit—is shunted by a circuit 
containing self-induction and capacity, there is spon- 
taneously set up in that shunt circuit an alternating 
current the frequency of which is determined by the 
“ natural’? frequency of the circuit. By the use of 
different inductions and capacities Mr. Duddell pro- 
duced alternating currents of various frequencies 
causing the arc to emit a musical note. The fre- 
quency of these vibrations was, however, low—as is 
shown by the fact of the arc emitting a note—and in 
wireless telegraphy the frequency must be high. 
Mr. Poulsen has found that by burning the arc in an 
atmosphere containing hydrogen, by lengthening the 
