May 5, 1923] 
that it would be practicable in an average year thus 
to supply a demand three times as great as the present 
demand in the whole of Ireland for electricity, and has 
recommended and shown the economy of linking up 
this supply to all important towns and cities ; utilising 
existing steam-electric stations to supply current when, 
owing to drought, one summer’s flow of the rivers is 
too far below the average summer flow. The combina- 
tion is like that at Chester, but on a much larger scale. 
Suppose we allocate part of each of the rivers Shannon 
and Erne to the manufacture of carbide and of nitrogen 
fertilisers and operate this plant as fully as the flow of 
water permits ; with an average output we could make 
in a year fertilisers containing 20,000 tons of nitrogen. 
_Each of these works would be of the size recommended 
as economical by the Nitrogen Products Committee of 
the Ministry of Munitions. 
It is not definitely known how much nitrogen fertiliser 
can be utilised within Ireland ; but there are markets 
for carbide and for nitrogen fertilisers outside Ireland, 
sO any excess over home requirements could be ex- 
ported at a profit. 
The nitrogen in various compounds used in a year in 
the world amounted to 694,600 tons? pre-War and 
1,219,000 tons post-War (1919). There is nothing 
excessive in recommending fixation in Ireland of 3 
per cent. of the world’s annual pre-War consumption 
of nitrogen. 
There would be work throughout the year, but more 
people employed at the chemical works in winter-time 
* American Electro-Chemical Society’s Proceedings, Volume 34. 
Pror. J. D. vAN DER WAALs. 
Wt Johannes Diderik van der Waals, who died 
on March 8 at Amsterdam, at eighty-five years 
of age, one of the great figures in the history of modern 
physics and physical chemistry has passed away. His 
thesis on the continuity of the liquid and gaseous state 
“was a revelation in the study of fluids, the remembrance 
of which was to glorify the golden jubilee of his doctorate 
next June, and after establishing it he continued for 
some forty years to apply his efforts to the same subject, 
_ marking the steps of his success by further brilliant 
discoveries. When the Nobel Institute honoured this 
lifework, van der Waals was still occupied rounding 
_ off the comprehensive views science owed to him. 
For about half a century he was in the front of the 
workers in the domain he had opened. In the ten 
years which separate us now from then his forces 
began to give way, and later bodily and mental suffer- 
ings, borne with modest resignation, set in. At last, 
only short visits allowed us to show to the venerated 
and beloved friend, whose heart we felt remained 
unchanged, what he had done for us. 
Van der Waals was born on November 23, 1837, 
at Leyden. He was a self-made man who took ad- 
vantage of the opportunities offered by the University 
which he later honoured by his curatorship. It was 
not until he was thirty-six years of age that he wrote 
his thesis. With it he himself opened the period of 
Dutch science, which his elder friend Bosscha and he 
hoped to be one of the results of secondary education. 
NO. 2792, VOL. 111] 

' NATURE 
609 

than in summer. It is well known that about 10,000 
workers leave Ireland every summer to do farming in 
Scotland and England and return to their more eco- 
nomical life in Ireland during the winter-time. For 
some of those there would be thus provided winter 
work in their own country; while, of course, there 
would be employment throughout the year for an 
appreciable number. 
There are nitrogen fixation plants near Niagara 
and at various other places in the world. About half 
of the pre-War consumption of nitrogen was in the form 
of native nitrate of soda. Among the many important 
applications of water-power, the one in Tasmania, 
where the Electrolytic Zinc Co. of Australasia, Ltd., 
utilises 30,000 horse-power from the Tasmanian 
Government Plant for the preparation of high-grade 
zinc, is worthy of especial mention. 
More attention should be paid to the selection of 
industries that require large amounts of power, and to 
their establishment at sites where suitable water-power 
is available. We cannot recall too often the history 
of Niagara’s development. Before electricity was a 
commercial form of energy, capital was invested (during 
the years 1853 to 1861) in making provision for direct 
water-power ; in 1861 it was ready, but it ran to 
waste for ten years before the first consumer arrived 
in 1871. It was not until 1894 (forty-one years after 
the commencement referred to) that a profitable 
amount of power was utilised. Water-power is the 
cheapest form of energy when fully utilised twenty- 
four hours in the day. 
Obituary. 
In 1877, van der Waals became a professor at Amster- 
dam, and began to exert his great influence on the 
development of Dutch physics. One of the character- 
istics of his highly admired teaching was the introduc- 
tion of Gibbs’s great work to the chemists. I vividly 
remember as an example of it how Bakhuis Roozeboom, 
to whose first experiments the Leyden physical 
laboratory had been in the position to give some help, 
obtained results, which were inexplicable until van 
der Waals came to give him the key to it in Gibbs’s 
doctrine of phases, his deep insight clearing the way 
for Roozeboom’s brilliant work on the phase rule. 
Very much was done by van der Waals for the Royal 
Academy of Sciences at Amsterdam. For twenty- 
four years he was the soul of the Board, and in 1896 
he even accepted the secretaryship of the Academy, 
a post which he filled until rgr2. Here as every- 
where else he showed a never-failing unselfishness and 
high conception of duty. We owe to him the modern 
form of the Proceedings and their English translation, 
which he directed, both with an incomparable energy. 
The great efforts he bestowed on these periodicals have 
been well rewarded by the effect their stimulating 
influence had on Dutch science. 
The scientific work of van der Waals forms a monu- 
mental whole of a special style. Characteristic of it is 
the intuition by which he introduced happy simplifica- 
tions and approximations leading to a high degree 
of qualitative agreement of his theories with Nature, 
which in the case of the law of corresponding states 
rose even to a surprising quantitative approximation. 
