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June 9, 1923] 
NATURE 
781 

sideration. I have pictured him writing my obituary | Iris with much regret that we record the death of 
notice ; I never thought the natural order would be 
reversed. HucGu Ropert Mitt. 

Pror. E. Hacen. 
Tue issue of the Phystkalische Zeitschrift for April 1 
contains the account of the life and work of the late 
Prof. E. Hagen given by Prof. E. Gtimlich at the meet- 
ing of the German Physical Society on March 9. Prof. 
Hagen was born at Konigsberg on January 31, 1851, 
and losing his mother, who was the youngest daughter 
of Bessel the astronomer, in 1856, was brought up by a 
stepmother for whom he had a lifelong affection. On 
the removal of his father to Berlin he became a pupil 
at the local Gymnasium and in 1871 entered the 
University. After two years there he went to Heidel- 
berg, where he graduated in 1875, having in the mean- 
time acted as assistant to Bunsen. The next two 
years he spent at Dresden as assistant to Toepler and 
a further six as assistant to Helmholtz at Berlin. 
In 1883 Hagen became a lecturer in the University 
of Berlin, and next year extra professor of applied 
physics at the Dresden Polytechnic. In 1887 he 
became physicist to the Navy and, removing to Kiel, 
acted also as extra professor at the University. In 
1893 he became director of the technical section of the 
Reichsanstalt at Charlottenburg. He married in 1896 
the daughter of Von Bezold the meteorologist, and in 
1904 joined the staff of the German Museum at Munich. 
He died of inflammation of the knee on January 15. 
He was best known in this country for his work in 
conjunction with Rubens on the connexion between the — 
electrical conductivity and the radiating and reflect- 
ing powers of metals. 
THE immense progress which has been made in the 
elucidation of crystal structure by means of X-rays, 
since the first discovery of von Laue at Munich in 
1912, and especially the quantitative development 
which has afforded the absolute distances separating 
the atoms, their actual sizes, and the dimensions of 
the space-lattice cells, is largely due to the invention 
‘of the ionising X-ray spectrometer by Sir William 
Bragg. The brilliant use made of that instrument at 
_ University College, London, and latterly also by an 
_ increasing number of other workers in various parts 
of the world, has been the means of accumulating a 
' surprising amount of knowledge of the structure and 
structural dimensions of a large number of substances, 
many of the more recently studied of which are no 
longer of the simplicity of those first submitted to 
investigation. It must prove of interest, therefore, to 
our readers that we are able to present, as a supple- 
ment to the present issue, a revised form of an 
admirable lecture which was recently delivered by 
Sir William Bragg to the Royal Society of Arts. 
_ The most noteworthy fact which emerges from the 
accumulated results, including those derived from 
the photographic method of Laue and the powder 
methods of Debye, Scherrer, and Hull, is that the 
conclusions of crystallographers, based on the most 
accurate crystal measurement and on the perfected 
2 NO. 2797, VOL. 111] 
Dr. Elizabeth Acton, on Sunday, May 13, after a pro- 
longed illness. Dr. Acton was a distinguished student 
_of the late Prof. G. S. West in the botanical department 
of the University of Birmingham. In 1908 she took 
her Bachelor of Science degree with honours, and in 
‘the following year received the M.Sc. for research work 
‘in botany. After that time she was almost con- 
‘tinuously engaged in botanical research, and in 1916 
was awarded the degree of D.Sc. (Birmingham). Her 
‘contributions to the study of fresh-water alge are of 
outstanding value, and her work throughout was 
‘marked by great thoroughness and _ painstaking 
‘accuracy. Her early death has removed a devoted 
worker from the sphere of botanical research. Dr. 
Acton’s activities outside her scientific work were 
necessarily limited, owing partly to her continuous 
ill-health and partly to her retiring disposition. She 
was a loyal friend, and her uncompromising honesty 
was one of her chief characteristics. J. SBE: 
Be ed 
WE regret to announce the following deaths : 
' Prof. J. Chiene, emeritus professor of surgery in 
the University of Edinburgh and a friend and 
disciple of Lord Lister, on May 29, aged eighty. 
Canon W. W. Fowler, president in 1901-2 of the 
Entomological Society, and author of ‘‘ The Coleoptera 
of the British Islands,” on June 3, aged seventy-four. 
Prof. Franz Neger, cassie of botany in the 
Dresden Technical College and director of the 
Botanical Gardens there, who worked with Baeyer 
for several years and published a thesis on de- 
hydracetic acid, aged fifty-four. 
Current Topics and Events. . 
geometrical theory of crystal structure, are proved to 
be correct, both as regards the nature of that structure, 
and its relative unit-cell dimensions in those few cases 
in which it had been possible to determine them. 
These relative dimensions are now converted into 
absolute values by the X-ray spectrometric measure- 
ments. The recent venture into the more difficult 
field of organic substances is adding a further chapter 
of exceptional interest, and is of immense importance 
both to chemistry and to optics. The results have 
already had the happy effect of restoring the mole- 
cule to its proper place in the solid state, from which 
only a misreading of the first few results with the 
simplest inorganic compounds had temporarily dis- 
placed it. Moreover, they have rendered it clear 
that the number, nature, and arrangement of the 
external electrons of the atom itself are involved in 
cementing together the parts of the crystal structure, 
so that further work is bound to throw light on 
atomic structure, and possibly to decide between, or 
combine the correct portions of, the rival theories 
concerning it. 
CrrcuLar No. 137, issued by the Bureau of Stand- 
ards, U.S.A., is the fourth of a series of circulars 
describing very simple radio receiving sets which 
were originally prepared for use by the Boys’ and 
