‘ 
eS 
DECEMBER 4, 1913} 
times arises as to whether the preparation is 
being sold as anhydrous radium bromide or 
radium bromide with its water of crystallisation. 
The radio-active department in the Reichs- 
anstalt has now been in operation for more than 
a year, under the charge of Dr. Geiger, whose 
radio-active researches in the University of Man- 
chester are well’ known. The creation of this 
department has been found to fill a much-needed 
want, and it is not too much to say that prac- 
tically all the radium and mesothorium that is 
bought and sold in Germany requires to-day the 
certificate of the Reichsanstalt. The number of 
standardisations required have increased very 
rapidly, and several assistants have been added 
to the department in charge of this work alone. 
There can be no doubt that the institution of a 
radio-active department in the National Physical 
Laboratory will prove of great service to this 
country, not only for scientific, but also for com- 
mercial purposes. It is well known that the 
buying and selling of radium in the past has been 
a very uncertain and risky procedure, for in most 
cases the radium content has not been expressed 
in terms of any authorised standard. This diffi- 
culty is removed by the present arrangement, and 
we should strongly recommend that those who 
wish to buy radium or mesothorium, whether for 
scientific or for medical purposes, should do so 
conditional on the certificate of standardisation 
from the National Physical Laboratory. 
It is understood that the work of testing and 
standardisation will be under the supervision of 
Dr. W. G. C. Kaye, of the National Physical 
Laboratory, whose pioneer work on the produc- 
tion and distribution of X-rays is well known to 
all physicists. The ability and skill in measure- 
ments which he has shown both in his work in 
the Cavendish Laboratory and in the National 
Physical Laboratory, afford the best of guarantees 
that the work of the new department will be 
carried out in a thoroughly satisfactory manner. 
E. RUTHERFORD. 
SIR ROBERT BALL, F-.R.S. 
OBERT STAWELL BALL was born in 
Dublin on July 1, 1840, the eldest son of 
Dr. Robert Ball, director of the Natural History 
Museum in the University of Dublin and secre- 
tary of the Queen’s University in Ireland. After 
attending school at Abbott’s Grange, Chester, 
he entered Trinity College, Dublin, in 1857. He 
became a mathematical scholar in 1860, Lloyd 
exhibitioner the same year, and graduated in 1861 
as gold medallist in mathematics, first gold 
medallist in experimental and natural sciences 
and University student in mathematics. To- 
wards the end of 1865 he went to Parsonstown 
as tutor to the three younger sons of the third 
Earl of Rosse and observer with the great six- 
foot and three-foot telescopes. When Ball began 
to use the six-foot reflector in February, 1866, 
nearly all the larger and more interesting nebule 
had been frequently observed and carefully drawn, 
NO. 2301, VOL. 92] 
© 
NATURE 
and he therefore chiefly devoted himself to work 
with the micrometer, a difficult task, since the 
telescope at that time had not yet been provided 
with a clock motion. He was the first observer 
with the instrument who corrected the measured 
position angles for the error due to the telescope 
not being equatorially mounted, but supported 
at the lower end on a universal joint. His obser- 
vations were included in the “Observations of 
Nebule, 1848-78,” published by the late Lord 
Rosse in 1879-80. 
In the autumn of 1867, shortly before the death 
of the maker of the great telescope, Ball was 
appointed professor of applied mathematics and 
mechanism at the newly established Royal College 
of Science for Ireland, in Dublin. He was sin- 
gularly well fitted for this post, as he was not 
only an excellent mathematician and had the 
power of elucidating even abstruse subjects in 
simple and clear language, but also possessed 
great skill in experimental work. In addition to 
his regular class work, he also sometimes gave 
evening lectures on mechanics in a more elemen- 
tary form, and in 1871 he published his first 
popular book, ‘‘ Experimental Mechanics,” which 
was very well received and showed his great 
aptitude both as a popular lecturer and as a 
writer. It led to his being much sought after 
as a lecturer; and as lectures on mechanics re- 
quired a large amount of apparatus, he preferred 
to lecture on popular astronomy, and by degrees 
he became the most successful lecturer on this 
subject, not only in this country, but in after 
years also in America. 
In January, 1870, Ball read a paper before the 
Royal Irish Academy on the small oscillations of 
a rigid body about a fixed point under the action 
of any forces. Out of this investigation grew 
the long series of memoirs which he published on 
the theory of screws in the course of the next 
thirty-four years, nearly all in the Trans. Roy. 
Irish Academy. This remarkable extension of 
theoretical dynamics, perhaps the most important 
contribution to that science since the introduction 
of couples by Poinsot, combines Poinsot’s force 
and couple into the single conception of a wrench 
on a screw, the latter being regarded merely as 
“4 directed straight line with an associated linear 
magnitude called the pitch.” The capabilities of 
the theory were gradually shown to be very great, 
as all the results of modern algebra and geometry 
appear to be applicable to it. Ball published a 
separate book on the subject in 1876, and in 
1889 Dr. Gravelius wrote a text-book in German, 
founded on Ball’s first eight memoirs. Finally, 
Ball’s great “Treatise on the Theory of Screws” 
appeared at Cambridge in 1900, but even after 
that date several succeeding memoirs showed that 
the author of the theory continued to devote his 
mind to its extension. 
The growing fame of Ball as a mathematician 
and the warm interest he was kaown to take in 
astronomy naturally led the Board of Trinity 
College to appoint him to the Andrews professor- . 
ship of astronomy in the University of Dublin, 
