About the Nobel Prize in Physics 1912
Gustaf DalénPresentation Speech by Professor H.G. Söderbaum, President of the Royal Swedish Academy of Sciences, on December 10, 1912
Your Majesty, Your Royal Highnesses, Ladies
and Gentlemen.
The Royal Academy of Sciences believes it is acting in strict
accordance with Alfred Nobel's will in awarding the Physics Prize
to Chief Engineer Gustaf Dalén in recognition of his
remarkable invention of automatic valves designed to be used in
combination with gas accumulators in lighthouses and
light-buoys.
The ever-growing use of maritime communication creates an
increased demand for navigational safety devices. Amongst these
devices lighthouses and light-buoys are of great importance, and
their number has become several times greater during the last few
decades. At the same time efforts have been made to find ways of
making their lights more powerful and their different lights more
easily distinguishable. As far as possible, work has been
directed towards finding a system which would regulate these
lights automatically. This is a very important point, for no
country is wealthy enough to maintain a continuous inspection of
all its necessary lighting equipment.
In Sweden, a country with a long coastline and large
archipelagos, the problem of a reliable and fairly inexpensive
lighting organisation has for a long time been more pressing than
elsewhere.
About 1895, for the first time it was discovered how to prepare
acetylene from calcium carbide on a commercial scale. Acetylene
is a gaseous hydrocarbon which, when burnt, produces an extremely
bright and white light.
The first attempt to use this gas for lighting in lighthouses did
not have very satisfactory results. The petroleum gas in use for
similar purposes up to this time had been compressed and enclosed
in large iron containers. It was found extremely dangerous to
treat acetylene in the same manner, as this gas, when under the
pressure of one or more atmospheres, explodes at the slightest
shock. It was also attempted to store calcium carbide in
lightbuoys and to let the acetylene escape under the action of
water supplied automatically. Unfortunately this method proved to
be inconvenient, not very reliable, and unusable in cold
weather.
In 1896, two French chemists, Claude and Hess, discovered that
acetone possesses the property of dissolving large quantities of
acetylene. This solution is not explosive. However, it cannot be
used as it is to store acetylene, because, even if the container
is filled to the brim with a saturated solution under high
pressure, the volume of the liquid is reduced by consumption or
by cooling, and explosive acetylene gas is produced in the space
above the surface of the liquid.
It was then discovered that its explosive nature disappears if
the acetylene solution is compressed in a porous mass. Numerous
unsuccessful attempts were made to prepare such a porous mass
which would be sufficiently resistant and elastic to withstand
the shocks encountered in transportation, without cracking and
crumbling and thus producing cavities filled with explosive
acetylene gas.
The credit for the eventual discovery of such a mass, called aga
or porous substance, belongs to Gustaf Dalén.
By a complicated and carefully developed process, this substance
is enclosed in steel containers which thus become practical
accumulators for the acetylene gas. The porous mass in the
container is half-filled with acetone, and acetylene is then
introduced by compressing it to a pressure of ten atmospheres.
Under this pressure, and at a temperature of 15° C, the
container contains one hundred times its own volume of acetylene.
The container is then ready for supplying to a lighthouse or
light-buoy the acetylene necessary for lighting.
The advantage of this arrangement would not be great if the
acetylene light had to burn uninterruptedly. On the one hand,
this form of lighting would be quite costly, and, on the other
hand, it would be difficult to distinguish the lights of various
lighthouses from one another and from other lightsources. True,
several methods of producing an intermittent light were already
known. For example, the flame can be surrounded by moving
screens, or the lighting device itself can be made to rotate. But
such arrangements need continual inspection and consequently
involve considerable expense.
Where compressed petroleum gas was used as the source of light,
eclipsing or flashing lighting devices had also been constructed
using the escaping gas as motive power. The flashes lasted 5 to 7
seconds, which was perhaps necessary because of the weak light
output of petroleum gas. But with the intense brightness of
acetylene light, such a long flash becomes unnecessary.
Furthermore, long flashes offer insufficient variation of the
signal. Accordingly the big lighthouses have generally replaced
them with lights giving flashes lasting from 1/10 to 3/10 of a
second.
It was about 1904 that Dalén started to study this problem.
With a petroleum gas apparatus it was impossible to divide one
litre of gas into more than fifty flashes. So Dalén
constructed an apparatus, based on an entirely new principle,
which by instantaneous opening and closing of the gas pipe,
enabled one litre of gas to provide several thousand very rapid
but distinct flashes. After a considerable trial period, this
ingenious device proved to be extremely reliable. Dalén then
provided a brilliant solution for the supplementary problems
arising from the use of aga light in the lighthouse service, and
an ever increasing number of lighthouses and light-buoys in
Sweden have been adapted to this form of lighting. The burner is
fitted with a small permanent flame which, in the most usual
arrangement, lights a flash every three seconds lasting 3/10 of a
second.
In 1907 Dalén crowned his achievement with a further
refinement by designing a kind of valve, called the "solar
valve", which extinguishes the light at sunrise and relights it
when night falls. This valve is controlled by four metal rods
enclosed in a glass tube. The lower one is blackened, while the
others are gilded and highly polished. Daylight is absorbed by
the blackened rod which is heated and consequently expands,
closing the gas valve. As the daylight decreases, the black rod
reaches the temperature of the other three rods: it contracts and
allows the gas valve to reopen.
The device can be regulated in such a way as to act with more or
less sensitivity. To be on the safe side, it is usually regulated
so that it lights as soon as mist or clouds cover the sun.
The solar valve combined with an intermittent light produces a
saving of gas of 93 per cent, and even greater economy might be
achieved by prolonging the periods between the flashes.
The use of aga light facilitates the placing of lighthouses and
lightbuoys in the most inaccessible places such as archipelagos
and seas with dangerous reefs. With the use of one or more of the
easily transportable gas accumulators, such lights can give their
warning or guiding signals for a whole year or more without the
need of inspection or the fear of failure.
The result is an entirely new standard of safety in navigation
and an enormous economy. For example, one shoal in Swedish waters
previously required a lightship costing approximately 200,000
Kronor and maintained at a cost of about 25,000 Kronor a year.
Now, in many cases, navigation is adequately served by
establishing an aga buoy with optical and audiosignalling
apparatus, the cost of which is 9,000 Kronor, and the annual
maintenance of which costs about 60 Kronor.
Most of the maritime nations have now started to install these
Dalén devices, and they are to be found operating from
Spitzberg, the Varanger Fjord, Iceland and Alaska in the north,
to the Straits of Magellan and Kerguelen Island in the south. The
annual benefit to navigation can be expressed in terms of saving
of thousands of human lives and of hundreds of millions of
Kronor.
The aga flame has proved to be extremely useful in other fields,
such as the lighting of railway coaches, railway signalling
apparatus, car head-lights, soldering, the casting and cutting of
metals and so on.
The Academy of Sciences recognizes the true value of all these
applications and wishes to emphasize those which contribute to
the progress of navigation, because it is uncontestably these
that have rendered the greatest benefit to humanity.
The sciences that were especially favoured in the will of the
great explosives technician Alfred Nobel, i.e. Physics,
Chemistry, and Medicine, have one common feature of involving and
sometimes demanding the sacrifice of the experimenter's personal
safety. We all know that this year's Physics Prize winner was the
victim of a serious accident which prevents him from being here
to receive the award from the hands of his King.
He is represented by his brother, Professor Albin Dalén, of
the Caroline Institute. Professor, when handing over to your
brother the medal and the diploma, I beg you also to convey to
him from the Royal Academy of Sciences, our sincere
congratulations on the distinction he has merited, and our best
wishes for a complete and speedy recovery.
From Nobel Lectures, Physics 1901-1921, Elsevier Publishing Company, Amsterdam, 1967
Copyright © The Nobel Foundation 1912
