3896 TRANSACTIONS OF SECTION A. 
II. The secondary rays excited in thick plates of different metals by 
alpha rays of constant intensity from polonium were measured by the 
electrical charge acquired under the emission of the secondary rays by the 
plates when insulated in high vacua. The following order of intensities 
was found fot the different metals :— 
Tntensity of 
é Secondary Rays 
Platinum . ‘ ; é Fi ; ; ‘ : A . 62:02 
Silver . : 3 7 P 6 Fi . ‘ . - 61:08 
Zine . ;: : 5 é ‘ A , 5 ‘ . 60°76 
Lead . . ‘ . ci 4 0 ‘ 0 4 - 59°85 
Copper . . : . . : 3 . . . . - 50°75 
a) os : : A ; 4 5 5 < : 5 . 49°48 
Aluminium . . . . . . . . . - 47:08 
III. The delta rays from deposits of polonium on the metals zinc, lead, 
aluminium, and copper were found to be proportional to the intensities of 
the alpha radiation from these deposits, 7.e., the delta radiation appeared 
to be independent of the metal which carried the deposit of polonium. 
IV. Considerations were presented which support the view that the delta 
radiation is produced by and accompanies the alpha particle in the course 
of its expulsion from the polonium atom. 
5. On some Phenomena associated with the Radiations from Polonium. 
By V. BE. Pounn, M.A. 
In this paper experiments were described dealing with the electrical 
charge acquired by an insulated metal plate B placed close to and facing 
an insulated copper plate A bearing a deposit of polonium. 
A series of curves was submitted which made it clear that, by the 
use of moderate electric and magnetic fields, at least three types of radiation 
were present and exerted an effect of greater or less degree on the charge 
acquired by the plate B, viz. (1), the alpha rays emitted by the plate A ; 
(2) an easily absorbed secondary radiation emitted by the plate B consisting 
of negatively charged particles; and (3) an easily absorbed delta radiation 
emitted by the plate A. 
With the application of high electric and magnetic fields, however, 
results were obtained which indicated the existence of a radiation which 
had hitherto escaped detection, of negatively charged particles from the 
polonium deposits. 
From the behaviour of this radiation under various conditions it was 
censidered to consist of streams of rest-atoms from the active product 
Radium G or polonium. 
6. Anode Rays and their Spectra. By Dr. Orto Rercuennem. 
See Reports, p. 124. 
7. On Clark and Weston Standard Cells. By H. L. Bronson, 'Ph.D., 
and A. N. Suaw, B.A. 
This paper dealt mainly with the accuracy and reproducibility of Clark 
and Weston cells, and it is hoped that it may throw further light on the 
value of the cell as one of the two legal electrical standards. 
The work has been very much facilitated by the courtesy of the Bureau 
of Standards at Washington, where one of the authors, at the suggestion of 
Dr. H. T. Barnes, spent some time in the summer vacation of 1908 in 
studying the construction of modern standard cells. At the invitation of 
