(1922. | Indian Science Congress. LS.C. 
Recent work on the Constilubion of ns Atom.—By E. P. 
Harrison, Ph.D , F.RB.S.E., : ti Ps 
To pene 
stillis the pine goal of the Natural Philose — Enormous adva 
in knowledge of the atom have occurred since Dalto n propounde “the 
Atomic Theory, but most = this advance has taken plies 
two ogee > a baa e be useful if I set before you a ver “0 brie ef 
account of ma a okoadl about 15 years on at the beginning of 
what 4 a oul call the ‘‘ present ’’ per 
at time, bss Cathode rays, which really faok the cal ne point 
of the shale story, had been proved to be ‘‘ particles”’ carrying a defi- 
nite —e of pees divcteicttg: and moving with a speed pate jisvh 
of — of light 
had become abundantly clear that the negative electron, as such 
a a rticle’’ was appropriately called, was a common constituent of all 
rms o at i e (48x 
wn forms of matter, that its harge was always the sa 10-10 
electrostatic units) and that its mass (7 x 10-28 gram) which was dc gps 
ed as being due wholly to its charge, ai ee in the ‘* field’ 
rounding it, increased as its speed incre 
These characteristics of the kage = ieee herir on the whole, 
truly experimental pesgenins: standin independent of those underlying 
s which have subsequently enabled the noncietens of amo 
ypothe 
plestrical charge to be Og oak theoretically on the basis of axecits 
eleetrom magnetic equaticns. 
At the 
common negatively 
universal and which 
a 
ee ‘ 
kno el ts differ in respect of the properties of their ome: Se 
logical conclusion was that the electron was a sub-atomic entity m cigs 
reco . esis at ioe 
gnized e t once noe as observable 
ar 
properties go, no change was to be ex xpected either in “the a 
iron. 
On that foundation the ae pres lem of ee “thought ha 
which now occupies so much of t iT can ae Shag te ; 
its first beginnings. The problem age, wee 
given these universal naaneo neh etait fee some ae of 
their properties, 
given the fact nies posi cba were at least 
oe Selig matter om i ; 
given also the enlaces of pmaee' and the Maxwell equations (already 
established = dantly), fulfil the 
an sini ok Sieee as a first approximation must fu 
Solicwin. condit 
1 
(1) In i various complexities de must explain the ome nr 
and the sequence of atomic weig' that is for oe 
2) I t Pa radiation, 
(2) * = eT eee d for spectral series and for the 
ts of chemical combination 
occasionally asso- 
Zeeman effect. 
(3) It must account for the main fac 
and valency of the elemen 
