534 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1926 
1906 he had developed the technique of the liquefaction of hydrogen 
on a large scale. In 1908 he attained the triumph of his career by 
liquefying helium. This feat, taking into consideration the limited 
supplies of helium and the difficulty in obtaining it in those days, 
was little short of superhuman. 
The amount of careful organization and planning necessary before 
the experiments were started can only be appreciated by those who 
have seen the laboratory in action. It is worthy of record that the 
whole staff was so tired out by their exertions that they could not 
see the helium even after it was liquefied. The presence of the liquid 
was pointed out to them by Prof. F. A. H. Schreinemakers, who was 
in the laboratory at the time. 
The boiling point of helium enabled Onnes to reach a temperature 
only 4.22° above absolute zero. By reducing the pressure he was 
finally enabled to arrive at a temperature of 0.9° absolute. The 
writer had the privilege of seeing Onnes attempt to solidify helium. 
A battery of 15 large Langmuir pumps were put into connection 
with a supply of liquid helium whereby the pressure was reduced to 
about 0.2 mm.; in spite of this, however, the helium did not solidify. 
The ability to control really low temperatures enabled Onnes to 
make the astonishing discovery of supraconductivity. It had always 
been assumed that the resistance of a metal would run out to nil 
at the absolute zero. Onnes discovered that quite a number of sub- 
stances showed a sharp discontinuity in their resistance curves at 
a temperature of about 4° or 5° absolute. Typical examples are lead 
and cadmium. He passed a current of 1,000 am./sq. mm. through a 
conductor under these conditions without being able to detect the 
slightest change of E. M. F. 
Onnes’s work is well summarized in the volume presented to him 
on the occasion of the fortieth anniversary of his holding the chair 
at the University of Leyden. Most of his work was published in 
the Proceedings of the Physical Laboratory of Leyden, and it is due 
to the comparative inaccessibility of this publication that Onnes’s 
work is not so widely known as it should be. 
It is impossible, within the limits of a brief notice, to give more 
than an idea of the scope and range of his activities. The division 
of the above-mentioned work into thermodynamic, magnetic, optical, 
magneto-optical, radioactive and electric subsections, in each of which 
he published numerous papers, is an indication of the magnitude of 
his work. 
In later life Onnes received the fullest recognition of his great 
talents. His own country awarded him a Commandership in the 
Order of the Lion of the Netherlands. Similar decorations were 
conferred upon him by the Governments of Poland and Norway. 
In 1913 he received a Nobel prize for physics. He was an honorary 
