APRIL 4, 1912] 
NATURE 
I reserve discussion of the possibility of this 
part of the peat being of more ancient date than 
that to which it has generally been referred—an 
opinion which might be suggested by the 
occurrence of Rhinoceros tichorhinus under the 
peat at Little Downham, or of the still older 
Elephas antiquus under the margin of the fen 
deposits near Whittlesea, and will content myself 
now with stating my own conviction that the peat 
in which the Shippea man was found cannot be 
older than Neolithic times, and may be much 
newer. 
Notwithstanding his Neanderthal character | 
should not be surprised to find that he was a man 
of much later date, even a monk from Ely, per- 
<a a 
oe 
omy rite ayirey , 
} P ~~ . 
haps a foreigner, who had lost his way and sunk 
down in the peaty swamp of the then undrained 
fens. 
T. McKenny HuGueEs. 
THE INTERNATIONAL RADIUM 
STANDARD. 
“T° HE committee formed at the Brussels Con- 
gress of Radiology and Electricity in Sep- 
tember, 1910, for the purpose of fixing an inter- 
national standard of radium, of which a full 
account appeared in Nature of October 6, 1910, 
met in Paris from March 25-28. There were 
present Mme. Curie, MM. Debierne, Ruther- 
ford, Soddy, Hahn, Meyer, and Schweidler. 
MM. Geitel, Eve, and Boltwood were unable 
to attend. The main purpose of the meet- 
ing was to compare the standard prepared 
by Mme. Curie with others prepared by 
NO. 2214, VOL. 89] 
115 
H6nigschmid from the material in possession of 
the Académie des Sciences at Vienna, during the 
course of his new determination of the atomic 
weight of radium, referred to in Nature of March 
21 (p. 68). Mme. Curie’s standard consisted of 
21°99 milligrams of radium chloride specially pre- 
_ pared by methods similar to those used by her 
| tinct methods. 
for atomic weight determination, and sealed up in 
a thin glass tube with every precaution against 
error. The Vienna standards consisted of three 
tubes, containing respectively 10°11, 31°17, 40°43 
milligrams of radium chloride, which were sealed 
up in somewhat wider glass tubes, but of the 
same thickness of wall (0°27 mm.) as the other, 
and were prepared by methods based on those 
devised by T. W. Richards for weighing hygro- 
| scopic substances. 
It may be recalled that Hénigschmid found the 
value 225°95 for the atomic weight of radium, 
which is 0°45 lower than that found by Mme. 
Curie. This is a difference of only 1 part in 500, 
and, considering the small amount of material, is 
probably not due to differences in the purity, 
/ especially as certain corrections, such as for the 
solubility of the silver chloride, were introduced 
into the calculation of the atomic weight from the 
later determinations. It was therefore of the 
greatest interest to compare directly these two 
sets of entirely independent standards. Mme. 
Curie was sufficiently recovered from her recent 
illness to take some part, both in the deliberations 
and measurements of the meeting. Prof. Ruther- 
ford was chosen as the president of the committee. 
After a visit to Mme. Curie’s laboratory in the 
rue Cuvier, the committee proceeded to the Sor- 
bonne, where, in Prof. Lippmann’s department, 
a room, uncontaminated by radium, had been set 
apart for the measurements. Here M. Debierne 
| had set up an interesting installation, capable of 
comparing the y-rays of the standards by two dis- 
The first method is based on the 
well-known null-method, largely employed in 
Paris, but hardly anywhere else, involving the 
quartz piézo-électrique of Pierre Curie. The ion- 
isation current due to the y-rays of the prepara- 
tion was balanced by the electricity generated by 
relieving the tension of a stretched quartz lamina, 
by gradually lifting a weight from the pan, the 
electrometer needle so being held to its zero and 
the time measured from the commencement to 
the end of the lifting of the weight. This requires 
practice, and the admirable skill of the French 
observers with the method was humorously illus- 
trated by the attempts of some of the visitors to 
emulate them. The form of ionisation chamber 
adopted calls for special remark. The radium 
standard was laid on the centre of a large circular 
disc of lead, 1 cm. thick, which formed the upper 
plate of a condenser, the distance between the 
| plates being small compared with their diameter. 
A potentional of S800 volts was used to ensure 
saturation. 
The other method was that recently described 
at the Physical Society by Rutherford and Chad- 
wick, and is also a null-method, the y-ray ionisa- 
