,libr>ies47                             
,a ,,brief ,,acc\nt ,,(                 
,,radio-,,activity                      
,,by                 ,,francis ,p4      
,,v5able1 ,,ph4,d41 ,d4,,sc41 ,,ll4,d4  
,,pr(essor ,,( ,,*emi/ry1 ,,univ]sity   
,,( ,,nor? ,,c>ol9a                     
,,au?or ,,(                     ,a      
,,%ort ,,hi/ory ,,( ,,*emi/ry1          
,,p]iodic ,,law1 ,,etc4                 
,d4 ,c4 ,,hea?  ,,co41 ,,publi%]s       
,,bo/on    ,,new ,,york    ,,*icago     
,,copyright1 #aiag1                     
,,by ,d4 ,c4 ,,hea?  ,,co4              
,,ia#g     ,,preface   ,i h ga!r$ !     
mat]ial = ?is little book because ,i h  
f\nd x a necess>y fill+ out ( ! c\rse = 
my class 9 g5]al *emi/ry4 ,su* a c\rse  
deal+ ) ! composition & /ructure ( matt]
 is left unf9i%$ & 9 ! air1 z x 71      
unless ! m>vell\s facts & d$uctions f ! 
/udy ( radio-activity are pres5t$ &     
discuss$4 ,! usual page or two giv5 9 ! 
pres5t text-books are too cond5s$ 9 _!  
treatm5t to af=d any intellig5t grasp ( 

! subject1 s ,i h put 9 book =m !       
lectures :i* ,i h hi!rto felt =c$ to    
give4  ,p]haps ! book may prove useful  
also to busy m5 9 o!r bran*es ( sci5ce  
:o wi% to "k some?+ ( radio-activity & h
 scant leisure 9 :i* to read ! l>g]     
treatises4  ,x is ne$less to say t !re  
is no?+ orig9al 9 ! book unless x be 9  
"p ! gr\p+ ( facts & ord] ( _! treatm5t4
 ,i h made free use ( ! writ+s (        
,ru!r=d1 ,soddy1 & ,j4 ,j4 ,?omson1 &   
w\ld "h express my debt to !m--j a "p ( 
t indebt$ness :i* we all feel to ^!     
ma/]s4 ,i wi% also to ackn[l$ge my      
obligations to ,pr(essor ,b]tram ,b4    
,boltwood = 8 helpful sugge/ions 9      
connection ) ?is "w4     ,,cont5ts      
,,*apt] ,i  ,,discov]y ,,(              
,,radio-,,activity                      
,,page      ,! beg9n+--,radio-active    
bodies--,an atomic                      
prop]ty--,discov]y ( new radio-active   
bodies--,discov]y     (                 
,polonium--,discov]y ( ,radium--,o!r    
radio-active     bodies f\nd            

#a  ,,*apt] ,,ii  ,,prop]ties ,,( ,,!   
,,radiations      ,ionization (         
,gases--,exp]im5tal                     
confirmation--,application     (        
electric field--,size & nature (        
ions--,photograph+     ! track ( !      
ray--,action ( radiations on            
photographic     plates--,dis*>ge (     
electrifi$ bodies--,sc9tillations     on
 phosphoresc5t bodies--,p5etrat+        
p[]--,magnetic     deflection--,?ree    
types ( rays--,alpha rays--,beta        
rays--,gamma     rays--,measurem5t (    
radiations--,id5tifications ( ! rays    
#g  ,,*apt] ,,iii  ,,*anges ,,9         
,,radio-,,active ,,bodies               
,radio-activity a p]man5t               
prop]ty--,induc$     activity--,discov]y
 ( ,uranium ,x--,conclusions            
drawn--,se>*     = new radio-active     
bodies--,me?ods ( inve/igation--,nature 
( !                                     
radiations--,life-p]iods--,equilibrium  
s]ies             #ag  ,,*apt] ,,iv     
,,nature ,,( ,,! ,,alpha ,,p>ticle      

,dis9tegrat+ ( ! elem5ts--,id5tification
 ( !     rays--,! alpha rays--,alpha    
rays consi/ ( solid                     
p>ticles--,electrical *>ge--,helium =m$ 
f alpha     p>ticles--,discov]y (       
,helium--,*>act]i/ics (                 
,helium--,table ( con/ants              
#be  ,,*apt] ,v  ,,! ,,/ructure ,,( ,,! 
,,atom      ,prop]ties ( ,radium--,en]gy
 evolv$ by radium--,necessity =     a   
dis9tegration !ory--,dis9tegration      
!ory--,con/itution     ( !              
atom--,ru!r=d's atom--,scatt]+ ( alpha  
p>ticles--,/opp+ p[] ( sub/ances        
#cb  ,,*apt] ,,vi  ,,radio-,,activity   
,,& ,,*emical ,,!ory      ,influ5ce ^u  
*emical !ory--,! p]iodic sy/em--,basis  
( ! p]iodic sy/em--,influ5ce ( positive 
nucleus--,det]m9ation ( ! atomic        
numb]--,use ( ,x-ray                    
spectra--,*anges caus$ by               
ray-emission--,atomic weight            
losses--,lead ! end product--,*anges (  
position     9 ! p]iodic sy/em--,*anges 
f loss ( beta                           

p>ticles--,isotopes--,radio-activity 9  
nature--,radio-active     products 9 !  
e>?'s cru/--,pres5ce 9 air & soil       
wat]s--,cosmical radio-activity         
#da  ,,index                            
#ec     ,a ,,brief ,,acc\nt ,,(         
,,radio-,,activity     ,,*apt] ,i       
,,discov]y ,,( ,,radio-,,activity   ,!  
object ( ?is brief treatise is to give a
 simple acc\nt ( ! developm5t ( our k ( 
radio-activity & its be>+ on *emical &  
physical sci5ce4 ,ma!matical processes w
 be omitt$1 z x is suffici5t to give !  
assur$ results f calculations :i* are   
likely to be beyond ! tra9+ ( ! read]4  
,exp]im5tal evid5ce w be giv5 9 detail  
:]ev] x is fundam5tal & necess>y to a   
confid5t grasp ( "s ( ! m>vel\s         
d$uctions 9 ?is new bran* ( sci5ce4     
,!ories _c be avoid$1 b ! facts rema9   
:ile !ories gr[ old & are disc>d$ = o!rs
 m 9 accord ) ! facts4   ,! ,beg9n+  ,z 
s (t5 happ5s 9 ! hi/ory ( sci5ce1 ! op5+
 up ( ?is new field ) its fasc9at+      
disclosures 0 due to an inve/igation    

und]tak5 = ano!r purpose b pa9/ak+ly    
c>ri$ out ) a m9d op5 to ! tru? :]ev] x 
might lead4  ,9 #ahie1 ,rntg5 mode/ly   
ann\nc$ 8 discov]y ( ! ,x rays4 ,?is    
attract$ imm$iate & int5se int]e/4      
,among ^? :o und]took to foll[ up ^!    
ph5om5a 0 ,becqu]el1 :o1 because ( !    
app>5t connection ) phosphoresc5ce1 tri$
 ! action ( a numb] ( phosphoresc5t     
sub/ances ^u ! photographic plate1 ! mo/
 /rik+ *>act]i/ic ( ! ,x rays be+ _!    
effect ^u su* s5sitive plates4 ,9 ^!    
exp]im5ts he obta9$ no results until he 
tri$ salts ( uranium1 recall+ previ\s   
obs]vations ( 8 z to _! phosphoresc5ce4 
,di/9ct action 0 not$4 ,fur!rmore1 he   
prov$ t ?is _h no connection ) !        
ph5om5on ( phosphoresc5ce1 z bo? uranic 
& uran\s salts 7 active & ! latt] %[ no 
phosphoresc5ce4 ,becqu]el ann\nc$ 8     
discov]ies 9 #ahif & ?is 0 ! beg9n+ ( ! 
new sci5ce ( radio-activity4            
,radio-active bodies  ,! rays giv5 (f by
 uranium & its salts 7 f\nd to diff] f !
 ,x rays4 ,!y %[$ no appreciable        

v>iation 9 int5sity1 no previ\s exposure
 ( ! sub/ance to light 0 necess>y1 &    
nei!r *anges ( temp]ature nor any o!r   
physical or *emical ag5cy affect$ !m4   
,at fir/ uranium & its comp\nds 7 ! only
 kn[n s\rce ( ^! new radiations1 b _m   
o!r sub/ances 7 exam9$ & two ye>s lat]  
?orium & its comp\nds 7 add$ to ! li/4  
,9 g5]al ! dis*>g+ action seem$ ab\t !  
same4 ,o!r elem5ts & ord9>y sub/ances %[
 a m9ute activity4 ,only potassium &    
rubidium h a great] activity ?an ?is1 & 
!irs is only ab\t "o-?\s&? t ( uranium4 
,an ,atomic ,prop]ty  ,9 ! exam9ation ( 
uranium & ?orium comp\nds x 0 f\nd t !  
activity 0 det]m9$ by ! uranium & ?orium
 pres5t2 x 0 proportto ! am\nt (ional ^!
 elem5ts pres5t & indep5d5t ( ! nature (
 ! o!r elem5ts compos+ ! comp\nd4 ,!    
conclusion 01 !re=e1 t ! activity 0 an  
inh]5t prop]ty ( ! atoms ( uranium &    
?orium1 t is1 an atomic prop]ty4 ,?is 0 
a long /ep =w>d & introduc$ into sci5ce 
! conception ( a new prop]ty ( matt]1 or
 at lea/ ( c]ta9 =ms ( matt]4           

,discov]y ( ,new ,radio-active ,bodies  
,9 exam9+ a l>ge numb] ( m9]als conta9+ 
uranium & ?orium1 ,mme4 ,curie made !   
important obs]vation t _m ( ^! 7 m      
active ?an ! elem5ts !mselves4 ,9       
measur+ ! activity %e made use ( !      
electrical me?od :i* w be describ$ lat]4
 ,9 ! foll[+ table giv+ h] results =    
uranium m9]als ! numb]s "u i give !     
maximum curr5t 9 amp]es4 ,!y s]ve simply
 = comp>ison4                           
i   ,pit*bl5de f ,joa*im/hal      #g4j  
#aj-aa   ,clevite                       
#a4d  #aj-aa   ,*alcolite               
#e4b  #aj-aa   ,autunite                
#b4g  #aj-aa   ,c>notite                
#f4b  #aj-aa   ,uranium                 
#b4c  #aj-aa   ,uranium & potassium     
sulphate     #j4g  #aj-aa   ,uranium &  
copp] phosphate       #j4i  #aj-aa  ,!  
la/ ?ree are pure uranium & comp\nds ( t
 elem5t giv5 = comp>ison ) ! fir/ five1 
:i* are naturally occurr+ m9]als4 ,! la/
 comp\nd has ! same composition z       
*alcolite & is simply ! artificially    

prep>$ m9]al4 ,x has ! activity :i* w\ld
 be calculat$ f ! proportion ( uranium  
pres5t1 ! copp] & phosphoric acid       
contribut+ no activity4  ,s9ce !        
activity is n dep5d5t ^u ! composition b
 ^u ! am\nt ( uranium pres5t1 ! activity
 9 all ( ! m9]als %\ld be less ?an t (  
uranium4 ,on ! contr>y1 x is sev]al     
times great]4 ,natural & artificial     
*alcolite also %[ a m>k$ diff]5ce 9     
favor ( ! =m]4 ,! supposition 0 a       
natural "o1 !re=e1 t ^! m9]als conta9$  
small quantities ( an elem5t1 or        
elem5ts1 undetect$ by ord9>y analysis & 
hav+ a mu* great] activity ?an uranium4 
,simil> results 7 obta9$ 9 ! exam9ation 
( ?orium m9]als & ?orium salts4         
,discov]y ( ,polonium  ,foll[+ up ?is   
supposition1 ,m4 & ,mme4 ,curie set     
!mselves ! task ( sep>at+ ?is unkn[n    
sub/ance4 ,/>t+ ) pit*bl5de1 a sy/ematic
 *emical exam9ation 0 made4 ,?is is an  
exce$+ly complex m9]al1 conta9+ _m      
elem5ts4 ,! processes 7 labori\s & dem&$
 mu* "t & m9ute c>e4 ,!y ne$ n be       

describ$ "h4 ,x is suffici5t to say t   
along ) bismu? a v active sub/ance 0    
sep>at$1 to :i* ,mme4 ,curie gave ! "n (
 polonium = ,pol&1 h] native l&4 ,its   
complete isolation is v difficult &     
suffici5t quantities ( ! pure sub/ance h
 n be5 obta9$ to det]m9e its atomic     
weight & o!r prop]ties1 b "s ( ! l9es ( 
its spectrum h be5 det]m9$4 ,*emically x
 is v closely analog\s to bismu?4       
,discov]y ( ,radium  ,9 a simil> mann] a
 b>ium precipitate 0 obta9$ f pit*bl5de 
:i* conta9$ a highly active sub/ance4 ,!
 pure *loride ( ?is body & b>ium c be   
prep>$ toge!r & !n sep>at$ by fractional
 cry/allization4 ,to ! new body ?us f\nd
 ! "n ( radium 0 giv54 ,x is simil> 9   
*emical prop]ties to b>ium4 ,its atomic 
weight has be5 det]m9$ by sev]al c>eful 
inve/igators & is accept$ z #bbf4 ,its  
spectrum has be5 mapp$ & its g5]al      
prop]ties are kn[n4 ,x is a silv]y :ite1
 oxidizable metal4 ,9 "o ton ( pit*bl5de
 ab\t #j4b gram ( radium is pres5t2 ?is 
is ab\t #ejjj times great] ?an ! am\nt (

 polonium pres5t4 ,! activity ( !       
products 0 dep5d$ ^u z ! guide 9 ^!     
sep>ations4 ,! radium f\nd is relatively
 enorm\sly m active ?an ! pit*bl5de or  
uranium4   ,o!r ,radio-active ,bodies   
,f\nd  ,9 ! above sep>ations use 0 made 
( relation%ips to bismu? & b>ium4       
,simil>ly1 by tak+ advantage ( *emical  
relation%ip to ! iron gr\p ( elem5ts1   
ano!r body 0 p>tially sep>at$ by        
,debi]ne1 to :i* he gave ! "n act9ium4  
,boltwood discov]$ 9 uranium m9]als !   
pres5ce ( a body :i* he nam$ ionium1 &  
:i* is s simil> to ?orium t x _c be     
sep>at$ f x4 ,x1 h[ev]1 f> exce$s ?orium
 9 activity4  ,! lead :i* is pres5t 9   
uranium & ?orium m9]als--app>5tly 9     
fairly def9ite ratio to ! am\nt (       
uranium & ?orium--is f\nd1 on sep>ation 
& purification1 to possess radio-active 
prop]ties4 ,?is activity is due to !    
pres5ce ( a v small proportion ( an     
active con/itu5t call$ radio-lead1 :i*  
has *emical prop]ties id5tical ) ^? (   
ord9>y lead4 ,! bulk ( ! lead obta9$ f  

radio-active m9]als diff]s 9 atomic     
weight f ord9>y lead & appe>s also to be
 diff]5t accord+ to :e!r its s\rce is a 
?orium or a uranium m9]al4  ,a l>ge     
numb] ( o!r radio-active sub/ances h be5
 sep>at$ & "s ( _! prop]ties det]m9$1 b 
^! 7 f\nd by diff]5t means & w be not$ 9
 _! prop] place4 ,!y numb] 9 all m ?an  
?irty4 ,! s\rces or p>5ts ( ^! are !    
orig9al uranium or ?orium1 & ! products 
=m regul> s]ies ) di/9ctive prop]ties = 
ea* memb]4     ,,*apt] ,,ii  ,,prop]ties
 ,,( ,,! ,,radiations   ,! activity ( ^!
 radio-active bodies consi/s 9 !        
emission ( c]ta9 radiations :i* may be  
sep>at$ into rays & /udi$ ?r\gh !       
ph5om5a :i* !y cause4   ,ionization (   
,gases  ,"o ( ^! ph5om5a is ! p[] ( =m+ 
ions or c>ri]s ( electricity by !       
passage ( ! rays ?r\gh a gas1 ?us ioniz+
 ! gas4 ,! details ( an exp]im5t w s]ve 
to make ! mean+ ( ?is ionization cle>4  
,illu/ration3 ,,fig4 #a4--;,,ionization 
,,( ,,gases4  ,:5 ?is app>atus is set up
 a m9ute curr5t w be obs]v$ )\t !       

introduction ( any radio-active matt]4  
,?is1 z ,ru!r=d says1 has be5 f\nd due  
ma9ly to a slight natural radio-activity
 ( ! matt] compos+ ! plates4 ,if        
radio-active matt] is spread on plate   
,a1 :i* is connect$ ) "o pole ( a gr\nd$
 batt]y1 & if plate ,b is connect$ ) an 
electromet] :i* is also connect$ ) !    
e>?1 a curr5t is caus$ :i* increases    
rapidly ) ! diff]5ce ( pot5tial betwe5 !
 plates1 !n m sl[ly until a value is    
rea*$ t *anges only slightly ) a l>g]   
increase 9 ! voltage4  ,accord+ to !    
!ory ( ionization1 ! radiation produces 
ions at a con/ant rate4 ,! ions c>ry+ a 
positive *>ge are attract$ to plate ,b1 
:ile ^? negatively *>g$ are attract$ to 
plate ,a1 ?us caus+ a curr5t4 ,^! ions w
 recomb9e & neutralize _! *>ges if !    
opportunity is giv54 ,! numb]1 !re=e1   
increases to a po9t at :i* ! ions       
produc$ balance ! numb] recomb9+4  ,:5  
an electric field is produc$ betwe5 !   
plates1 ! velocity ( ! ions betwe5 !    
plates is increas$ 9 proportion to !    

/r5g? ( ! electric field4 ,9 a weak     
field ! ions travel s sl[ly t mo/ ( !m  
recomb9e on ! way & consequ5tly ! obs]v$
 curr5t is v small4 ,on increas+ !      
voltage ! spe$ ( ! ions is increas$1    
few] recomb9e1 ! curr5t increases1 &1 :5
 ! condition = recomb9ation is          
practically remov$1 x w h a maximum     
value4 ,?is maximum curr5t is call$ !   
saturation curr5t & ! value ( ! pot5tial
 diff]5ce requir$ to give ?is maximum   
curr5t is call$ ! saturation ,p4,d4 or  
saturation voltage4  ,! picture1 !n1 is 
?is4 ,! radiations sep>ate ! compon5ts (
 ! gas into ions1 or c>ri]s (           
electricity1 half ( :i* are *>g$        
negatively & half positively4 ,9 !      
electric field ^? negatively *>g$ seek !
 positive plate & ^? positively *>g$    
seek ! negative plate4 ,if "t is giv51  
^! ions meet & recomb9e1 _! *>ges are   
neutraliz$1 & !re is no curr5t4         
,exp]im5tal ,confirmation  ,?is !ory ( !
 ionization ( gases has be5 mo/         
int]e/+ly confirm$ by direct exp]im5t4  

,= in/ance1 ! ions may =m nuclei = !    
cond5sation ( wat]1 & 9 ?is way !       
exi/5ce ( ! sep>ate ions 9 ! gas may be 
%[n & ! numb] pres5t actually c\nt$4    
,:5 air saturat$ ) wat] vapor is all[$  
to exp& sudd5ly1 ! wat] pres5t =ms a mi/
 ( small globules4 ,!re are always small
 du/ p>ticles 9 air & ar\nd ^! z nuclei 
! drops are =m$4 ,^! drops w settle &   
?us by repeat$ small expansions all du/ 
nuclei may be remov$ & no mi/ or cl\d w 
be =m$ by fur!r expansions4  ,if n[ !   
radiation f a radio-active body be      
introduc$ into ! cond5sation vessel1 a  
new cl\d is produc$ 9 :i* ! wat] drops  
are f9] & m num]\s accord+ to ! int5sity
 ( ! rays4 ,on pass+ a /rong beam (     
light ?r\gh ! cond5sation *amb]1 ! drops
 c readily be se54 ,^! drops =m on !    
ions produc$ by ! radiation4            
,application ( ,electric ,field  ,if !  
cond5sation *amb] has two p>allel plates
 = ! application ( an electric field l t
 already describ$1 ! ions w be c>ri$ at 
once to ! electrodes & disappe>4 ,!     

rapidity ( ?is action dep5ds ^u ! /r5g? 
( ! electric field & exp]im5t %[s t !   
/rong] ! field ! small] ! numb] (       
cond5sation drops =m$4 ,if !re is no    
electric field1 a cl\d c be produc$ "s  
"t aft] ! %utt+ (f ( ! s\rce (          
radiation1 %[+ t "t is requir$ = !      
recomb9ation ( ! ions4   ,size & ,nature
 ( ,ions  ,if ! drops are c\nt$ 7!re be+
 special me?ods = ?is7 & ! total curr5t 
c>ri$ accurately measur$1 !n ! *>ge     
c>ri$ by ea* ion may be calculat$4 ,?is 
has be5 det]m9$4 ,! mass ( an ion comp>$
 ) ! mass ( ! molecules ( gas 9 :i* x 0 
produc$ c also be approximately e/imat$4
 ,9 ! /udy ( ^! ions ! view has be5 held
 t ! *>g$ ion attract$ to itself a clu/]
 ( molecules :i* surr\nd$ ! *>g$ nucleus
 & travel$ ) x4 ,x is r\ghly e/imat$ t  
ab\t ?irty molecules ( ! gas clu/] ar\nd
 ea* *>g$ ion4   ,photograph+ ! ,track (
 ! ,ray  ,utiliz+ ! fact t ^! ions ) _! 
clu/]s ( molecules =m nuclei = !        
cond5sation ( wat] vapor1 ,c4 ,t4 ,r4   
,wilson has by in/antane\s photography  

be5 able to photograph ! track ( an     
ioniz+ ray ?r\gh air4 ,! numb] ( ! ions 
produc$1 & h5ce ! numb] ( drops1 is s   
great t ! trail is %[n z a cont9u\s l9e4
 ,9 ! copy ( ?is photograph x w be se5 t
 at "s di/ance f its s\rce ! /raight    
trail is slightly b abruptly b5t4 ,ne> !
 end ( its c\rse !re is ano!r abrupt &  
mu* %>p] b5d4 ,^! b5ds %[ :]e ! ioniz+  
ray1 9 ?is case an alpha p>ticle1 has   
be5 deflect$ by m or less direct        
collision ) an atom4 ,^! collisions & ! 
f9al disappe>ance ( ! ray w be discuss$ 
lat]4      ,illu/ration3 ,,fig4         
#b4--,,photograph ,,( ,,! ,,track ,,(   
,,an     ,,ioniz+ ,,ray4   ,action (    
,radiations on ,photographic ,plates    
,tak+ up n[ o!r means ( exam9+ ^!       
radiations1 x is well to consid] _!     
action ^u a photographic or s5sitive    
plate4 ,x w be recall$ t ?is 0 ! me?od  
by :i* _! exi/5ce 0 orig9ally detect$4  
,to illu/rate ! me?od1 ! foll[+ acc\nt (
 h[ "o su* photograph 0 tak5 may be     
giv54  ,! plate 0 wrapp$ 9 two          

?icknesses ( black pap]4 ,! objects 7   
plac$ ^u ?is & ! radio-active ore1      
sep>at$ by a bo>d "o in* ?ick1 0 plac$  
above4 ,! exposure la/$ five days4 ,!   
action is mu* less rapid & ! result n s 
cle>ly def9$ z 9 ! case ( photographs   
tak5 by ,x rays4 ,( c\rse1 ! removal ( !
 bo>d & ! use ( m conc5trat$ prep>ations
 ( radium w\ld give quick] & bett]      
results4 ,! me?od1 h[ev]1 on acc\nt ( "t
 consum$ & lack ( def9ition is ill      
adapt$ to accurate "w4                  
,illu/ration3 ,,fig4 #c--,,photograph   
,,( ,,v>i\s ,,objects ,,tak5     ,,by   
,,means ,,( ,,pit*bl5de   ,dis*>ge (    
,electrifi$ ,bodies  ,! radiations f    
radio-active bodies c dis*>ge bo?       
positively & negatively electrifi$      
bodies by mak+ ! air surr\nd+ !m a      
conductor ( electricity4 ,to demon/rate 
?is1 use is made ( an electroscope4 ,if 
! h+$ leaf ( su* an in/rum5t be         
electrically *>g$ & a radio-active body 
be br\ght into its neighborhood1 !      
electricity w be dis*>g$ & ! leaf return

 to its orig9al position4 ,! rapidity ( 
?is dis*>ge is us$ to measure ! degree (
 activity ( ! body giv+ (f ! radiation4 
,illu/ration3 ,,fig4 #d4--;,,gold-,,leaf
 ,,electroscope4      ,! gold-leaf ,l is
 atta*$ to a flat rod ,r & is           
insulat$ inside ! vessel by a piece (   
amb] ,s support$     f ! rod ,p4 ,!     
sy/em is *>g$ by a b5t rod ,,cc'        
pass+ ?r\gh an ebonite /opp]4 ,aft]     
*>g+1 x is     remov$ f contact ) !     
gold-leaf sy/em4 ,! rods ,p     & ,c & !
 cyl9d] are !n connect$ ) ! e>?4        
,sc9tillations on ,phosphoresc5t ,bodies
  ,x 0 f\nd by ,crookes t a scre5 cov]$ 
) phosphoresc5t z9c sulphide 0 brightly 
light$ up :5 expos$ to ! radiations4    
,?is is due to ! bomb>dm5t ( ! z9c      
sulphide by a type ( ray call$ ! alpha  
ray4 ,"u a magnify+ glass ?is light is  
se5 to be made up ( a numb] ( sc9tillat+
 po9ts ( light & is n cont9u\s1 ea*     
sc9tillation be+ ( v %ort duration4 ,by 
prop] subdivision ( ! field "u ! l5s1 ! 
numb] ( sc9tillations c be c\nt$ ) close

 accuracy4  ,a simple =m ( app>atus     
call$ ! sp9?>iscope has be5 devis$ to %[
 ^! sc9tillations4 ,a z9c sulphide scre5
 is fix$ 9 "o end ( a small tube & a    
plate c>ry+ a trace ( radium is plac$ v 
close to x4 ,! sc9tillations c be obs]v$
 ?r\gh an adju/able l5s at ! o!r end ( !
 tube4 ,out] light %\ld be cut (f1 z 9 a
 d>k room4 ,! scre5 !n appe>s to be     
cov]$ ) brilliant fla%es ( light4 ,o!r  
phosphoresc5t sub/ances1 su* z b>ium    
plat9o-cyanide1 may be sub/itut$ = ! z9c
 sulphide1 b !y d n answ] s well4       
,p5etrat+ ,p[]  ,by p5etrat+ p[] is     
meant ! p[] exhibit$ by ! rays ( pass+  
?r\gh solids ( diff]5t ?icknesses &     
gases ( v>i\s dep?s4 ,?is p[] v>ies )   
diff]5t radiations & ) ! nature ( !     
solid or gas4 ,= in/ance1 a %eet (      
metallic foil may be us$ & ! effect (   
alum9um w diff] f t ( gold & ! diff]5t  
rays v>y 9 p5etrat+ p[]4 ,9 ! case (    
gases air w diff] f hydrog51 & x is     
notic$ t c]ta9 rays disappe> aft]       
p5etrat+ a %ort di/ance1 :ile o!rs c    

p5etrate fur!r be=e be+ lo/4   ,magnetic
 ,deflection  ,if ! radiations are      
subject$ to ! action ( a /rong magnetic 
field1 x is f\nd t "p ( !m are mu*      
deflect$ 9 ! magnetic field & describe  
circul> orbits1 "p are only slightly    
deflect$ & 9 ! opposite direction f !   
fir/1 & ! rema9+ rays are entirely      
unaffect$4      ,illu/ration3 ,,fig4    
#e4--,,%[+ ,,magnetic ,,deflection ,,(  
alpha1 beta1 ,,& gamma ,,rays4   ,?ree  
,types ( ,rays  ,by ! use ( ^! me?ods ( 
inve/igation x is le>n$ t ! radiations  
consi/ ( ?ree types ( rays4 ,^! h be5   
nam$ ! alpha1 beta1 & gamma rays1       
respectively4 ,"s radio-active bodies   
emit all ?ree types1 "s two1 & "s only  
"o4 ,! di/+ui%+ *>act]i/ic ( ^! types ( 
rays may be summ$ up z foll[s3   ,alpha 
,rays  ,! alpha rays h a positive       
electrical *>ge & a comp>atively l[     
p5etrat+ p[]4 ,!y are slightly deflect$ 
9 /rong magnetic & electric fields4 ,!y 
h a great ioniz+ p[] & a velocity ab\t  
"o-fifte5? t ( light4   ,beta ,rays  ,! 

beta rays are negatively *>g$ & h a     
great] p5etrat+ p[] ?an ! alpha rays4   
,!y %[ a /rong deflection 9 magnetic &  
electric fields1 h less ioniz+ p[] ?an !
 alpha rays1 & a velocity ( ! same ord] 
z light4   ,gamma ,rays  ,! gamma rays  
are v p5etrat+ & are n deflect$ 9 !     
magnetic or electric fields4 ,!y h !    
lea/ ioniz+ p[] & a v great velocity4   
,! p5etrat+ p[] ( ea* type is complex & 
v>ies ) ! s\rce1 s ! /atem5ts giv5 are b
 g5]alizations4 ,! alpha rays are       
project$ p>ticles :i* lose en]gy 9      
p5etrat+ matt]4 ,z to ! p[] ( ioniz+    
gases1 if t = ! alpha rays is tak5 z    
#aj1jjj1 !n ! beta rays w\ld be         
approximately #ajj & ! gamma rays #a4   
,measurem5t ( ,radiations  ,! rays are  
exam9$ & measur$ 9 sev]al ways3  #a4 ,by
 _! action on ! s5sitive photographic   
plates4 ,! use ( ?is me?od is labori\s1 
consumes "t1 & = comp>ative measurem5ts 
( int5sity is unc]ta9 z to effect4  #b4 
,by electrical me?ods1 us+              
electroscopes1 quadrant electromet]s1   

etc4 ,^! are ! me?ods mo/ us$4  #c4 ,by 
exposure to magnetic & electric fields1 
not+ ext5t & direction ( deflection4    
#d4 ,by _! relative absorption by solids
 & gases4  #e4 ,by ! sc9tillations on a 
z9c sulphide scre54   ,id5tification ( !
 ,rays  ,! alpha rays h be5 id5tifi$ z  
simil> to ! s-call$ canal rays4 ,^! 7   
fir/ obs]v$ 9 ! /udy ( ! ,x rays4 ,:5 an
 electrical dis*>ge is pass$ ?r\gh a    
vacuum tube ) a ca?ode hav+ holes 9 x1  
lum9\s /reams pass ?r\gh ! holes t[>d ! 
side away f ! anode & ! g5]al direction 
( ! /ream4 ,!y travel 9 /raight l9es &  
r5d] c]ta9 sub/ances phosphoresc5t4 ,^! 
rays are slightly deflect$ by a magnetic
 field & 9 an opposite direction f t    
tak5 by ! ca?ode rays 9 _! deflection4  
,! rays seem to be positive ions )      
masses nev] less ?an t ( ! hydrog5 atom4
 ,_! s\rce is unc]ta91 b !y may be d]iv$
 f ! electrodes4  ,! beta rays are      
id5tical 9 type ) ! ca?ode rays & are   
negative electrons4  ,! gamma rays are  
analog\s to ! ,x rays & are ( ! ord] (  

light4 ,!y are 9 g5]al consid]ably m    
p5etrat+ ?an ,x rays4 ,= example1 !     
gamma rays s5t out by #cj milligrams (  
radium c be detect$ by an electroscope  
aft] pass+ ?r\gh #cj c5timet]s ( iron1 a
 mu* great] ?ickness ?an c be p5etrat$  
by ! ord9>y ,x rays4     ,,*apt] ,,iii  
,,*anges ,,9 ,,radio-,,active ,,bodies  
,is ,radio-activity a ,p]man5t ,prop]ty8
  ,is ?is p[] ( emitt+ radiations a     
p]man5t prop]ty or is x lo/ ) ! passage 
( "t8 ,! fir/ inve/igations ( ! activity
 ( uranium & ?orium %[$ no loss (       
int5sity at ! end ( sev]al ye>s1 &      
radium also seem$ to %[ no decrease 9   
its enorm\s activity4 ,polonium1 h[ev]1 
0 f\nd to lose mo/ ( its activity 9 a   
ye>1 & lat] x appe>$ t "s radio-active  
sub/ances lo/ mo/ ( _! activity 9 !     
c\rse ( a few m9utes or h\rs4   ,induc$ 
,activity  ,a ph5om5on call$ induc$ or  
second>y radio-activity 0 also obs]v$4  
,?us a metal plate or wire expos$ to !  
action ( ?orium oxide = "s h\rs became  
itself active4 ,?is induc$ activity 0 n 

p]man5t b decreas$ to half its value 9  
ab\t elev5 h\rs & practically disappe>$ 
)9 a week4 ,simil> ph5om5a 7 obs]v$ :5  
radium 0 sub/itut$ = ?orium4   ,discov]y
 ( ,uranium ,x  ,9 #aijj ,crookes       
precipitat$ a solution ( an active      
uranium salt ) ammonium c>bonate4 ,!    
precipitate 0 dissolv$ s f> z possible 9
 an excess ( ! reag5t1 leav+ an         
insoluble residue4 ,?is residue 0 _m    
hundr$ times m active1 weight = weight1 
?an ! orig9al salt1 & ! solution conta9+
 ! salt 0 practically inactive4 ,at !   
end ( a ye> ! uranium salt _h rega9$ its
 activity :ile ! residue _h become      
inactive4  ,ano!r me?od ( obta9+ ! same 
result is to dissolve cry/alliz$ uranium
 nitrate 9 e!r4 ,two lay]s ( solution   
are =m$1 "o e!r & ! o!r wat] com+ f !   
wat] ( cry/allization4 ,! aque\s lay] is
 active1 :ile ! wat] lay] is inactive4  
,simil>ly1 by add+ b>ium *loride        
solution to a solution ( a salt (       
uranium & !n precipitat+ ! b>ium z      
sulphate1 ! activity is transf]r$ to ?is

 precipitate4 ,^! exp]im5ts give pro( ( 
! =mation & sep>ation ( a radio-active  
body by ord9>y *emical op]ations4  ,s1  
too1 9 ! case ( ?orium salts a sub/ance 
c be obta9$ by means ( ammonium         
hydroxide :i* is sev]al ?\s& times m    
active ?an an equal weight ( ! orig9al  
salt4 ,aft] /&+ a mon?1 ! sep>at$       
mat]ial has lo/ its activity & ! ?orium 
salt has rega9$ x4 ,"h1 aga91 !re is !  
=mation1 sep>ation1 & loss ( a          
radio-active body4   ,conclusions ,drawn
  ,n[1 ^! are ord9>y *emical processes =
 ! sep>ation ( di/9ct *emical           
individuals4 ,! results1 !re=e1 lead    
naturally to ! conclusions3 7#a7 x w\ld 
seem t uranium & ?orium are !mselves    
inactive & ! activity is due to "s o!r  
sub/ance =m$ by ^! elem5ts2 7#b7 ?is    
active sub/ance is produc$ by "s        
trans=mation 9 ^? elem5ts1 = on /&+ !   
activity is rega9$4 ,?is latt]          
conclusion is />tl+1 = x indicates a    
*ange 9 ! atom :i*1 up to ! "t ( ?is    
discov]y1 0 deem$ un*angeable "u !      

influ5ce ( su* physical & *emical *anges
 z 7 kn[n to u4   ,se>* = ,new          
,radio-active ,bodies  ,! se>* = new    
radio-active bodies & ! /udy ( _!       
*>act]i/ics has be5 sy/ematically &     
successfully c>ri$ on4 ,! bodies obta9$ 
9 ! above exp]im5ts 7 nam$ uranium ,x & 
?orium ,x1 respectively4 ,fur!r1 x      
became cle> f ! inve/igation ( uranium  
m9]als t radium1 polonium1 act9ium1 &   
ionium orig9at$ f uranium4 ,f ?orium    
m9]als a body 0 sep>at$ call$           
meso?orium1 :i* 0 analog\s to radium4   
,bo? ?orium & radium 7 f\nd to give (f a
 radio-active gas4 ,! fir/ lo/ half (   
its activity 9 less ?an "o m9ute4 ,!    
second 0 m /able & lo/ half ( its       
activity 9 ab\t f\r days4 ,! "n radium  
emanation 0 giv5 to ! latt] & x 0 f\nd  
*emically & physically to belong to !   
class ( monatomic or noble gases1 su* z 
helium1 argon1 neon1 etc41 :i* _h be5   
discov]$ by ,ramsay4 ,9 "s cases !      
*emical action 0 det]m9$ & ^! new bodies
 7 f\nd analog\s to well-kn[n elem5ts1 z

 radium to b>ium1 polonium to bismu?4 ,!
 physical prop]ties 7 inve/igat$ &1 :]e 
possible1 spectra 7 mapp$ & atomic      
weights det]m9$4  ,x is cle>1 !re=e1 t  
^! bodies are elem5tal 9 "* & z su* are 
made up ( di/9ct1 simil> atoms1 j z !   
commonly recogniz$ elem5ts are believ$  
to be4 ,9 ?is way m ?an ?irty new       
elem5ts h be5 add$ to ! li/4 ,^! new    
elem5ts are call$ radio-active elem5ts1 
b x is an op5 "q :e!r all atoms d n     
possess ?is prop]ty 9 great] or less    
degree4 ,c]ta9ly1 x is possess$ 9 v>y+  
degree by f\r ( ! old elem5ts widely    
sep>at$ 9 ! ,p]iodic ,sy/em1 namely1    
uranium1 ?orium1 rubidium1 & potassium4 
,! la/ two1 :ile feebly active !mselves1
 d n =m any second>y radio-active       
sub/ance s f> z is kn[n4 ,only two ( !  
elem5ts1 !n1 c def9itely be said to g   
?r\gh ^! trans=mations4 ,x is j possible
 t radio-activity may be f\nd to be a   
common prop]ty ( all atoms & ( all      
matt]4   ,me?ods ( ,inve/igation  ,x is 
important to "k h[ ^! new bodies 7      

discov]$ & di/+ui%$ f "o ano!r4 ,two    
prop]ties are reli$ ^u4 ,"o is ! nature 
( ! rays emitt$ & ! o!r is ! duration ( 
! activity4 ,( c\rse1 k ( ! physical &  
*emical prop]ties is also ( great       
importance :5ev] obta9able4   ,nature ( 
! ,radiations  ,! nature ( ! radiation  
is a di/+ui%+ *>act]i/ic1 ?\gh simil>ity
 "h does n prove id5tity ( sub/ances4   
,"s emit alpha rays only1 "s emit beta  
rays1 "s emit two ( ! possible rays1 z =
 in/ance1 beta & gamma1 & "s emit all   
?ree4 ,! rays may also diff] 9 !        
velocity ) :i* !y are emitt$ by diff]5t 
radio-active sub/ances4 ,?us1 9 ! case (
 "o sub/ance ! alpha rays may h a       
slightly great] or less p5etrat+ p[] ?an
 ^? emitt$ by "s o!r sub/ance1 & ?is may
 be true also ( ! o!r rays4   ,life     
,p]iods  ,! duration ( ! activity is    
call$ ! life p]iod4 ,?is is absolutely  
fix$ = ea* body & furni%es ! mo/        
important mode ( diff]5tiat+ among !m4  
,x measures ! relative /ability & is !  
"t :i* mu/ elapse be=e _! activity is   

lo/ & !y1 *ang+ into some?+ else1       
entirely disappe>4 ,! measure usually   
adopt$ is ! half-value p]iod4 ,two      
hypo!ses are made use (3  #a4 ,t !re is 
a con/ant production ( fre% radio-active
 matt] by ! radio-active body4  #b4 ,t !
 activity ( ! matt] s =m$ decreases     
accord+ to an expon5tial law ) ! "t f ! 
mom5t ( its =mation4  ,^! hypo!ses agree
 ) ! exp]im5tal results4 ,! decrease &  
rise ( activity1 = example1 ( uranium & 
uranium ,x1 & also ( ?orium & ?orium ,x1
 h be5 measur$1 plott$1 & ! equations   
work$ out4  ,manife/ly1 a /ate (        
equilibrium w be rea*$ :5 ! rate ( loss 
( activity ( ! matt] already produc$ is 
balanc$ by ! activity ( ! new matt]     
produc$4 ,?is equilibrium & ! k ( ! rate
 ( decrease 9 g5]al w h little value if 
?is rate1 l *emical *anges1 is subject  
to ! influ5ce ( *emical & physical      
conditions4 ,! rate ( decrease has be5  
f\nd to be unalt]$ by any kn[n *emical  
or physical ag5cy4 ,= in/ance1 nei!r !  
highe/ temp]atures applicable nor ! cold

 ( liquid air h any appreciable effect4 
,equilibrium ,s]ies  ,9 ord] to measure 
! dis9tegration ( a radio-active body 9 
units ( "t s t ! rate may be comp>able )
 t ( o!r radio-active bodies1 ! relation
 betwe5 ! am\nts "u consid]ation mu/ be 
a def9ite "o4 ,= ?is purpose equal      
weights ( ! bodies are n tak51 b use is 
made ( ! am\nts :i* are 9 equilibrium ) 
a fix$ am\nt ( ! p>5t sub/ance4  ,"o    
gram ( radium has be5 settl$ ^u z ! /&>d
 = t s]ies & a unit kn[n z ! curie has  
be5 adopt$ to express ! equilibrium     
quantity ( radium emanation4 ,?us1 a    
curie ( radium emanation 7or niton7 is !
 weight 7or1 z ?is is a gas1 ! volume at
 /&>d pressure & temp]ature7 ( !        
emanation 9 equilibrium ) "o gram (     
radium4 ,?is1 by calculation & exp]im5t1
 is f\nd to be #j4fc cubic millimet]4   
,:5 ?is am\nt has be5 produc$ by "o gram
 ( radium1 ! =mation & decay w exactly  
balance "o ano!r4 ,?is is1 !re=e1 "o    
curie ( emanation4  ,! measurem5t ( !   
rate ( decay is difficult b c be c>ri$  

out ) great accuracy1 ev5 d[n to        
seconds1 9 ! case ( c]ta9 %ort-liv$     
bodies4 ,errors crept 9 at fir/ f !     
failure to completely sep>ate !         
sub/ances produc$ 9 ! s]ies1 & sometimes
 because ( ! simultane\s production (   
two sub/ances4  ,z /at$1 ! decay foll[s 
an expon5tial law4 ,! "t requir$ = !    
decay ( activity to half-value does n   
mean1 !re=e1 t !re w be total decay 9   
twice t "t4 ,?us ! half-value p]iod =   
uranium ,x is ab\t #bb days4 ,! p]iod = 
complete decay is ab\t #afj days4 ,?is  
half-value p]iod corresponds to !       
half-value recov]y p]iod ( uranium1 :i* 
is also #bb days4  ,^! 7 ! e>li] figures
 obta9$ = uranium ,x & !y illu/rate "s (
 ! difficulties surr\nd+ su*            
det]m9ations4 ,x 0 f\nd lat] t ! body   
exam9$ z uranium ,x 0 really a con/ant  
mixture & ( c\rse ! decay & recov]y     
p]iods 7 also composite4 ,x requir$ lat]
 & v skilful "w to sep>ate !m into !    
bodies indicat$ 9 ! dis9tegration s]ies4
  ,! half-value p]iod = ?orium ,x is mu*

 %ort]1 namely1 a little ov] f\r days1 &
 ?is is also ! recov]y p]iod = ?orium   
,x4 ,! plott$ decay & recov]y curves w  
int]sect at ?is po9t4  ,! consecutive   
dis9tegration s]ies1 ) ! half-value     
p]iods1 = ! uranium & ?orium s]ies z    
giv5 by ,soddy are se5 9 ! foll[+       
tables4 ,!y are probably subject to "s  
*anges on fur!r & m accurate            
det]m9ation4 ,! nature ( ! rays emitt$  
is also giv54      ,illu/ration3        
,uranium 7#h  #aji ye>s7                
#bch4e    - alpha                       
- alpha                                 
_/     ,uranium ,x 7#ce4e days7         
7#bcj4e7  - betagamma                   
- 7beta7                                
_/                                      
_/                                      
_/      ,ionium 7#e  #ajd to #ajf ye>s7 
7#bcj4e7  - alpha                       
_/     ,radium 7#b1ejj ye>s7            
#bbf4d    - alpha                       
_/     ,emanation 7#e4eg days7          
7#bbb4d7  - alpha                       

_/     ,radium ,a 7#d4c m9utes7         
7#bah4d7  - alpha                       
_/     ,radium ,b 7#ch4e m9utes7        
7#bad4d7  - 7beta7                      
_/     ,radium ,c#a 7#bh4a m9utes7      
7#bad4d7  - alpha                       
- betagamma                             
_/     ,radium ,c#b 7#a4i m9utes7       
7#baj4d7  - betagamma                   
_/     ,radium ,d 7#bd ye>s87           
7#baj4d7  - 7beta7                      
_/     ,radium ,e 7#g4be days7          
7#baj4d7  - betagamma                   
_/     ,radium ,f 7,polonium #bjb days7 
7#baj4d7  - alpha                       
_/     ,radium ,g 7probably lead7       
7#bjf4h7       ,act9ium 787             
_/     ,radio-,act9ium 7#bh4a days7     
- alpha                                 
- 7beta7                                
_/     ,act9ium ,x 7#ae days7           
- alpha                                 
_/     ,emanation 7#e4f seconds7        
- alpha                                 
_/     ,act9ium ,a 7#j4jjbi second7     

- alpha                                 
_/     ,act9ium ,b 7#eb4a m9utes7       
- 7beta7                                
_/     ,act9ium ,c#a 7#c4aj m9s47       
- alpha                                 
_/     ,act9ium ,c#b 787                
- alpha                                 
_/     ,act9ium ,d 7#g4d m9utes7        
- betagamma                             
_/     ,act9ium ,e 7unkn[n7             
,?orium 7#d  #ajaj ye>s87     #bcb4d    
- alpha787                              
_/     ,meso?orium#a 7#g4i ye>s7        
_/     ,meso?orium#b 7#h4i h\rs7        
- betagamma                             
_/     ,radio?orium 7#b4ia ye>s87       
- alpha                                 
_/     ,?orium ,x 7#e4ce days7          
- alpha                                 
_/     ,emanation 7#gf seconds7         
- alpha                                 
_/     ,?orium ,a 7#j4bjc second7       
- alpha                                 
_/     ,?orium ,b 7#ae4c h\rs7          
- 7beta7                                

_/     ,?orium ,c#a 7#gi m9utes7        
- alpha                                 
_/     ,?orium ,c#b 787                 
- alpha                                 
_/     ,?orium ,d 7#d4e m9utes7         
- betagamma                             
_/     ,?orium ,e 7unkn[n7      ,,fig4  
#f4--;,,dis9tegration ,,s]ies ,,=       
,,uranium1 ,,act9ium1 ,,&     ,,?orium1 
,,z ,,giv5 ,,by ,,soddy4     ,,*apt]    
,,iv  ,,nature ,,( ,,! ,,alpha ,,p>ticle
   ,dis9tegration ( ! ,elem5ts  ,!      
rem>kable dis9tegrations relat$ 9 ! la/ 
*apt]1 9 :i* ! heavie/ kn[n elem5t>y    
atom--t ( uranium 7at4 wt4 #bch7--;is by
 successive /ages *ang$ into o!rs ( l[] 
atomic weight1 af=d a clue to ! nature (
 ! atom & to t goal ( ! *emi/1 ! f9al   
con/itution ( matt]4 ,! composite nature
 ( ! atom & "s sort ( int]relation ( !  
elem5ts _h previ\sly be5 made app>5t f a
 /udy ( ! ,p]iodic ,sy/em & data ga!r$  
/ill e>li]1 b all attempts at work+ out 
a s-call$ g5esis ( ! elem5ts _h prov$   
vague & unsatisfactory4   ,id5tification

 ( ! ,rays  ,to get an und]/&+ ( !      
dis9tegration occurr+ 9 radio-active    
sub/ances1 ! nature ( ! rays produc$ mu/
 be kn[n4 ,^! rays are ! cause ( !      
activity & _! emission accompanies !    
*anges or dis9tegration4 ,!y h = ! sake 
( conv5i5ce be5 call$ ! alpha1 beta1 &  
gamma rays4 ,! gamma rays h be5 id5tifi$
 ) ! ,x rays discov]$ by ,rntg5 & are a 
=m ( en]gy analog\s to light4 ,! beta   
rays are p>ticles ( negative electricity
 or electrons4 ,) ^!1 !n1 we h "s degree
 ( famili>ity4 ,b :at are ! alpha rays8 
,an answ] to ?is "q %\ld make cle>] ! "*
 ( ! *anges tak+ place1 & %\ld give "s  
insight into ! composition & me*anism ( 
! atom4   ,! ,alpha ,rays  ,x has       
already be5 /at$ t ^! alpha rays are    
simil> or analog\s to ! canal rays1 b   
?is advances ! matt] v little1 z !      
nature ( ^! canal rays has n be5 fully  
det]m9$4 ,! full id5tity ) !m1 if prov$1
 %\ld h an important !oretical be>+4    
,alpha ,rays ,consi/ ( ,solid ,p>ticles 
,9 ! fir/ place1 ^! alpha rays h be5    

f\nd to be made up ( solid p>ticles1 t  
is1 ( :at we are accu/om$ to call matt]4
 ,s9ce x has become m & m difficult to  
draw a cle> di/9ction betwe5 matt] &    
en]gy1 x w\ld p]haps be bett] to say t  
^! p>ticles appe> to h "s ( ! prop]ties 
hi!rto attribut$ solely to matt]4 ,! be/
 evid5ce t ^! p>ticles are ( atomic mass
 is furni%$ by _! deflection 9 electric 
& magnetic fields4   ,electrical ,*>ge  
,x is n ( fir/ importance to discuss ?is
 or o!r pro(s ( ! mat]ial nature ( ^!   
p>ticles4 ,t !y c>ry a *>ge ( positive  
electricity is1 h[ev]1 a fact ( v great 
import4 ,! value ( ?is *>ge has be5     
c>efully det]m9$ by a numb] (           
inve/igators work+ ) diff]5t s\rces ( ! 
alpha p>ticles & has be5 f\nd to be #i4c
  #aj-aj electro/atic units             
74#jjj1jjj1jjj1ic e4s474 ,f !           
consid]ation ( ! *>ge ^u an electron    
previ\sly obta9$ by ,j4 ,j4 ,?omson &   
o!rs1 x 0 conclud$ t ! alpha p>ticle    
c>ri$ two unit positive *>ges2 !        
fundam5tal unit *>ge1 !re=e1 is half ?is

 value1 or #d4fe  #aj-aj e4s4   ,helium 
,=m$ f ,alpha ,p>ticles  ,to det]m9e !  
nature ( ! alpha p>ticle a crucial      
exp]im5t 0 c>ri$ out by ,ru!r=d &       
,royds1 :i* 0 describ$ z foll[s3        
,illu/ration3 ,,fig4 #g4--;,,app>atus   
,,us$ ,,9 ,,exp]im5t ,,by     ,,ru!r=d  
,,& ,,royds4  ,a l>ge quantity ( radium 
emanation 0 compress$ into a f9e glass  
tube ,a1 ab\t #a4e cm4 long4 ,?is tube1 
:i* 0 seal$ to a l>g] capill>y tube ,b1 
0 suffici5tly ?9 to all[ ! alpha        
p>ticles f ! emanation & its products to
 pass ?r\gh1 b suffici5tly ?ick to )/&  
atmosph]ic pressure4 ,! ?ickness ( !    
glass wall 0 9 mo/ cases less ?an 4#ja  
mm4 ,on introduc+ ! emanation into !    
tube1 ! escape ( ! alpha p>ticles f !   
emanation 0 cle>ly se5 by !             
sc9tillations produc$ at "s di/ance on a
 z9c sulphide scre54 ,aft] ?is te/ !    
glass tube ,a 0 surr\nd$ by a glass tube
 ,t & a small spectrum tube ,v atta*$ to
 x4 ,! tube ,t 0 exhau/$ to a *>coal    
vacuum4 ,by means ( ! m]cury column ,h1 

! gases 9 ! tube ,t c\ld at any "t be   
compress$ into ! spectrum tube ,v & !   
nature ( ! gases :i* _h be5 produc$     
det]m9$ spectroscopically4 ,x 0 f\nd t  
two days aft] ! introduction ( !        
emanation into ,a ! spectrum %[$ ! yell[
 l9e ( helium1 & aft] six days ! :ole   
helium spectrum 0 obs]v$4 ,9 ord] to be 
c]ta9 t ! helium1 com+ possibly f "s o!r
 s\rce1 _h n diffus$ ?r\gh ! ?9 walls ( 
! tube ,a1 ! emanation 0 pump$ out &    
helium sub/itut$4 ,no trace ( helium    
c\ld be obs]v$ 9 ! vacuum tube aft]     
sev]al days1 %[+ t ! helium obs]v$ 9 !  
fir/ exp]im5t mu/ h orig9at$ f ! alpha  
p>ticles :i* _h be5 propell$ ?r\gh ! ?9 
glass tube into ! out] tube4  ,mo/ ( !  
alpha p>ticles are propell$ ) su* =ce t 
!y p5etrate "s di/ance into ! walls ( ! 
out] tube & "s ( ^! gradually diffuse   
out into ! exhau/$ space4 ,! pres5ce (  
helium 9 ! spectrum tube c be detect$   
aft] a %ort] int]val if a ?9 cyl9d] (   
lead is plac$ ov] ! emanation tube1 s9ce
 ! p>ticles fir$ into ! lead diffuse out

 m rapidly ?an f glass4  ,a /ill m      
def9ite pro( ( ! id5tity ( ! alpha      
p>ticle ) ! helium atom 0 obta9$ by     
remov+ ! out] glass tube ,t & plac+ a   
cyl9d] ( lead ov] ! emanation tube 9 !  
op5 air4 ,helium 0 always detect$ 9 !   
lead aft] x _h rema9$ sev]al h\rs ov] ! 
?9 tube conta9+ a l>ge quantity ( !     
emanation4 ,9 ord] to te/ = ! pres5ce ( 
helium 9 ! lead1 ! gases pres5t 7       
releas$ by melt+ ! lead 9 a clos$       
vessel4 ,!re c ?us be no d\bt t ! alpha 
p>ticle becomes a helium atom :5 its    
positive *>ge is neutraliz$4  ,?us !    
*emi/ 0 af=d$ ! exp]i5ce ( ! build+ up (
 at lea/ "o elem5t "u 8 obs]vation1 &   
bo? ! analysis & syn!sis ( matt] h be5  
reveal$ ?r\gh ! discov]ies (            
radio-activity4   ,discov]y ( ,helium   
,x is ( int]e/ at ?is po9t to le>n      
some?+ ( ! hi/ory ( helium & its        
occurr5ce4 ,9 #ahfh !re 0 discov]$ by   
,janss5 & ,locky] a bright yell[ l9e 9 !
 spectrum ( ! sun's *romosph]e4 ,because
 ( its orig9 ! "n helium 0 giv5 to !    

suppos$ new elem5t caus+ x4 ,lat] x 0   
f\nd 9 ! spectra ( _m ( ! />s1 & because
 ( its pr$om9ance 9 "s ( ^! !y 7 call$  
helium />s4 ,its exi/5ce on our planet 0
 n detect$ = ne>ly ?irty ye>s4  ,9      
#ahie1 9 connection ) ! discov]y ( argon
 9 ! atmosph]e1 a se>* 0 made to see if 
! latt] elem5t c\ld be obta9$ f m9]al   
s\rces4 ,9 analyz+ c]ta9 uranium m9]als 
,hillebr& _h f\nd consid]able quantities
 ( a gas :i* he took to be a peculi> =m 
( nitrog54 ,ramsay made a fur!r         
exam9ation ( ! gas com+ f ^! m9]als & ! 
spectroscope reveal$ ! yell[ l9e (      
helium1 ?us at la/ prov+ ! pres5ce ( ?is
 elem5t on ! e>?4 ,x is kn[n n[ to be   
pres5t 9 ?orium m9]als1 9 ! wat]s (     
radio-active wells1 & 9 m9ute am\nts 9 !
 atmosph]e4 ,its occurr5ce 9 e case1 9 !
 light ( ! exp]im5t describ$ above1 w\ld
 seem to be due to ! pres5ce (          
radio-active *anges4   ,*>act]i/ics (   
,helium  ,helium1 on acc\nt ( its       
*emical inactivity & physical prop]ties1
 is class$ along ) argon1 neon1 krypton1

 & x5on 9 ! z]o gr\p ( ! ,p]iodic       
,sy/em1 & =ms ) !m ! monatomic1 in]t    
gases4 ,9 ?is class are n[ plac$ also ! 
?ree radio-active gases1 emanat+        
respectively f radium1 ?orium1 &        
act9ium4 ,^! are g5]ally kn[n z radium  
emanation1 ?orium emanation1 & act9ium  
emanation4 ,! fir/ m5tion$ 0 once call$ 
niton4 ,emanium 0 ! "n orig9ally propos$
 by ,giesel = ! body n[ kn[n z act9ium4 
,! calculat$ rate ( production ( helium 
9 ! s]ies 9 equilibrium ) "o gram (     
radium is #aeh cubic millimet]s p] ye>4 
,?is corresponds q well ) ! exp]im5tal  
results4   ,table ( ,con/ants  ,"s ( ! m
 important atomic & radio-active        
con/ants are giv5 9 ! foll[+ table4 ,!y 
are record$ "h to %[ h[ helpful ! /udy (
 radio-activity has be5 9 work+ out !   
composition ( matt]1 & to give "s idea (
 ! magnitude ( ! numb]s & ! m9ut5ess ( !
 quantities dealt )4    ,electric *>ge  
c>ri$ by ea* ,h atom 9                  
electrolysis                            
#d4fe  #aj-aj e4s4#a   ,electric *>ge   

c>ri$ by ea* alpha         p>ticle      
#i4c   #aj-aj e4s4   ,numb] ( atoms 9 #a
 gram ( ,h              #f4b   #ajbc    
,mass ( #a atom ( ,h                    
#a4f   #aj-bd gram   ,numb] ( molecules 
p] cc4 ( any gas at         /&>d        
pressure & temp]ature     #b4gb  #ajai  
,numb] ( alpha p>ticles expell$ p]      
second p] gram ( radium itself      #c4f
   #ajaj   ,numb] ( alpha p>ticles      
expell$ p]         second p] gram (     
radium 9         equilibrium ) its      
products        #ad4c   #ajaj     #a ,! 
expression #aj-aj means multiply+ by    
4#jjj1jjj1jjj1a2    #ajaj means         
multiply+ by #aj1jjj1jjj1jjj4           
,,*apt] ,v  ,,! ,,/ructure ,,( ,,!      
,,atom   ,prop]ties ( ,radium  ,a /udy (
 ! prop]ties ( radium w aid 9 ?r[+ light
 ^u ! "q z to ! build+ up ( ! atom4     
,fir/ to be consid]$ are ! usual        
prop]ties :i* di/+ui% an elem5t>y body4 
,metallic radium has be5 prep>$ by a    
me?od simil> to t us$ 9 ! prep>ation (  
b>ium4 ,x is a pure :ite metal1 melt+ at

 #gjj1 & f> m volatile ?an b>ium4 ,x    
rapidly alt]s on exposure to ! air1     
probably =m+ a nitride4 ,x en]getically 
decomposes wat] & ! product dissolves 9 
! wat]4 ,its atomic weight is #bbf4     
,radium =ms a s]ies ( salts analog\s 9  
appe>ance & *emical action to ^? (      
b>ium4 ,9 ! c\rse ( "t !y become color$1
 especially if mix$ b>ium salts4 ,!     
radiations f radium produce m>k$ *emical
 effects 9 a numb] ( sub/ances4 ,c>bon  
dioxide is *ang$ into c>bon1 oxyg51 &   
c>bon monoxide1 & ! latt] is *ang$ into 
c>bon & oxyg54 ,ammonia is dissociat$   
into nitrog5 & hydrog52 hydro*loric acid
 into *lor9e & hydrog54 ,oxyg5 is       
cond5s$ into ozone4 ,9 g5]al1 ! action  
^u gases appe>s to be simil> to t ( !   
sil5t electric dis*>ge4 ,wat] is        
decompos$ into hydrog5 & oxyg54 ,if moi/
 radium *loride or a salt ( radium      
conta9+ wat] ( cry/allization is seal$ 9
 a glass tube1 ! gradual accumulation ( 
hydrog5 & oxyg5 w bur/ ! tube4  ,!      
radiations rapidly decompose organic    

matt] ) ! evolution ( gases4 ,?us grease
 f /opcocks ( app>atus us$ ) radium or  
p>aff9 w give (f c>bon dioxide4 ,"u an  
int5se alpha radiation p>aff9 or vasel9e
 become h>d & infusible4 ,:ite          
phosphorus is *ang$ into r$4  ,! action 
^u liv+ tissue is mo/ notewor?y1 z its  
possible use z a rem$ial ag5t is dep5d5t
 ^u ?is4 ,a small am\nt ( a radium salt 
enclos$ 9 a glass tube w cause a s]i\s  
burn on fle% expos$ to x4 ,x !re=e has  
to be h&l$ ) c>e & undue exposure to !  
radiations mu/ be avoid$4 ,canc] sacs   
%rivel up & practically disappe> "u its 
action4 ,:e!r ! de/ruction ( :atev]     
causes ! canc] is complete is at lea/   
op5 to s]i\s d\bt4  ,! coagulat+ effect 
^u globul9 is int]e/+4 ,:5 two solutions
 ( globul9 f ox s]um are tak5 & acetic  
acid add$ to "o :ile ammonia is add$ to 
! o!r1 ! opalesc5ce 9 drops ( ! =m] is  
rapidly dim9i%$ on exposure to radium1  
%[+ a m complete solution1 :]eas ! latt]
 solution rapidly turns to a jelly &    
becomes opaque1 indicat+ a greatly      

decreas$ solubility4   ,en]gy ,evolv$ by
 ,radium  ,! great] "p ( ! trem5d\s     
en]gy evolv$ by radium is due to !      
emission ( ! alpha p>ticles1 & 9        
comp>ison ! beta & gamma rays toge!r    
supply only a small fraction4 ,?is en]gy
 may be measur$ z heat4 ,x 0 fir/ obs]v$
 t a radium comp\nd ma9ta9$ a temp]ature
 sev]al degrees high] ?an t ( ! air     
ar\nd x4 ,! rate ( heat production 0    
lat] measur$ by means ( an ice          
calorimet] & also by not+ ! /r5g? ( !   
curr5t requir$ to raise a comp>ison tube
 ( b>ium salt to ! same temp]ature4 ,bo?
 me?ods %[$ t ! heat produc$ 0 at ! rate
 ( ab\t #ace gram calories p] h\r4 ,z ! 
emission is cont9u\s1 "o gram ( radium  
w\ld !re=e emit ab\t #a1ahj1jjj gram    
calories 9 ! c\rse ( a ye>4 ,at ! end ( 
#bjjj ye>s x w\ld /ill emit #eij1jjj    
gram calories p] ye>4 ,su* a production 
( en]gy s f> surpasses all exp]i5ce t x 
becomes almo/ inconceivable4 ,x is      
futile to speak ( x 9 t]ms ( ! heat     
evolv$ by ! combu/ion ( hydrog51 :i* is 

! greate/ t c be produc$ by *emical     
means4  ,?is effect is unalt]$ at l[    
temp]atures1 z has be5 te/$ by imm]s+ a 
tube conta9+ radium 9 liquid air4 ,x    
%\ld be /at$ t ^! measurem5ts 7 made    
aft] ! radium _h rea*$ an equilibrium ) 
its products2 t is1 aft] wait+ at lea/ a
 mon? aft] its prep>ation4 ,! evolution 
( heat f radium & ! radio-active        
sub/ances is1 9 a s5se1 a second>y      
effect1 z x measures ! radiant en]gy    
trans=m$ into heat en]gy by ! active    
matt] itself & :atev] surr\nds x4 ,let u
 repeat1 !re=e1 t ! total am\nt ( en]gy 
p5t up 9 a s+le atom ( radium almo/     
passes our p[]s ( conception4           
,necessity = a ,dis9tegration ,!ory  ,! 
facts ga!r$ s f> ju/ify & necessitate a 
!ory :i* %all satisfactorily expla9 !m1 
& s9ce ^! ph5om5a are n caus$ by nor    
subject to ! influ5ce ( ext]nal ag5cies1
 !y mu/ ref] to *anges tak+ place )9 !  
atom--9 o!r words1 a !ory (             
dis9tegration4 ,9 ! ma91 ^! facts may be
 summ$ up z ! emission ( c]ta9          

radiations f kn[n elem5tal matt]3 !     
mat]ial alpha p>ticles ) positive *>ge1 
! beta p>ticles or negative electrons1 &
 ! gamma rays analog\s to ,x rays4 ,!   
emission ( ^! rays results 9 !          
production ( great heat4 ,!n !re is !   
law ( trans=mations by :i* :ole s]ies ( 
new elem5ts are g5]at$ f ! orig9al      
elem5t & ma9ta9 a con/ant equilibrium ( 
gr[? & decay 9 ! s]ies4 ,la/ly1 we h !  
production ( helium f ! alpha p>ticles4 
,dis9tegration ,!ory  ,9 explanation (  
^! ph5om5a1 ,ru!r=d (f]$ ! hypo!sis t ! 
atoms ( c]ta9 elem5ts 7 un/able &       
subject to dis9tegration4 ,! only       
elem5ts def9itely kn[n to come "u ?is   
description are ! two hav+ atoms ( !    
greate/ kn[n mass1 ?orium 7#bcb7 &      
uranium 7#bch74  ,! atoms ( uranium1 =  
in/ance1 are suppos$ to be n p]man5t b  
un/able sy/ems4 ,accord+ to ! hypo!sis1 
ab\t #a atom 9 e #ajah becomes un/able  
ea* second & breaks up ) a viol5t       
explosion = s small a mass ( matt]4 ,"o1
 or possibly two alpha p>ticles are     

expell$ ) great velocity4 ,?is alpha    
p>ticle corresponds to an atom ( helium 
) an atomic weight ( #d1 & its loss     
r$uces ! orig9al atomic weight to #bcd )
 ! =mation ( a new elem5t1 hav+ *ang$   
prop]ties correspond+ to ! new atomic   
weight4 ,?is new elem5t is uranium ,x#a4
  ,^! new atoms are f> m un/able ?an ^? 
( uranium1 & ! decomposition proce$s at 
a new rate ( #a 9 #ajg p] second4 ,s at 
a def9ite1 measurable rate ?is /epwise  
dis9tegration proce$s4 ,! explosions are
 n 9 all cases equally viol5t 9 go+ f   
elem5t to elem5t1 nor are ! results !   
same4 ,sometimes alpha p>ticles alone   
are expell$1 sometimes beta1 or two ( !m
 toge!r1 z alpha & beta4  ,! new product
 may rema9 ) ! un*ang$ "p ( ! orig9al   
matt]4 ,?us !re w\ld be an accumulation 
( x until its own decay balances its    
production1 result+ ev5tually 9 a /ate (
 equilibrium4   ,con/itution ( ! ,atom  
,9 ord] to expla9 ! electrical & optical
 prop]ties ( matt]1 ! hypo!sis 0 made t 
! atom consi/$ ( positively & negatively

 electrifi$ p>ticles4 ,lat] x 0 %[n t   
negative electrons exi/ 9 all k9ds (    
matt]4 ,v>i\s attempts 7 made to "w out 
a model ( su* an atom 9 :i* ^! p>ticles 
7 held 9 equilibrium by electrical =ces4
 ,! atom ( ,"l ,kelv9 consi/$ ( a uni=m 
sph]e ( positive electrification ?r\gh\t
 :i* a numb] ( negative electrons 7     
di/ribut$1 & ,j4 ,j4 ,?omson has det]m9$
 ! prop]ties ( ?is type z to ! numb] (  
p>ticles1 _! arrangem5t & /ability4     
,ru!r=d's ,atom  ,accord+ to ,ru!r=d1 ! 
atom ( uranium may be look$ ^u z consi/+
 ( a c5tral *>ge ( positive electricity 
surr\nd$ by a numb] ( conc5tric r+s (   
negative electrons 9 rapid motion4 ,!   
positively *>g$ c5tre is made up ( a    
complicat$ sy/em 9 movem5t1 consi/+ 9 "p
 ( *>g$ helium & hydrog5 atoms1 &       
practically ! :ole *>ge & mass ( ! atom 
is conc5trat$ at ! c5tre4 ,! c5tral     
sy/em ( ! atom is f "s unkn[n cause     
un/able1 & "o ( ! helium atoms escapes f
 ! c5tral mass z an alpha p>ticle4  ,!re
 are1 confess$ly1 difficulties connect$ 

) ?is conception ( ! atom :i* ne$ n1    
h[ev]1 be discuss$ "h4 ,mu* rema9s to be
 le>n$ z to ! me*anics ( ! atom1 & !    
hypo!sis outl9$ above w probably h to be
 mat]ially alt]$ z k gr[s4 ,p]haps x may
 h to be entirely ab&on$ 9 favor ( "s m 
satisfactory solution4 ,until su* "t x  
at lea/ suffices z a m5tal picture ar\nd
 :i* ! kn[n facts gr\p !mselves4 ,9 ?is 
picture en]gy & matt] lose _! old-"t    
di/9ctness ( def9ition4 ,discrete       
subdivisions ( en]gy are recogniz$ :i*  
may be call$ *>g$ p>ticles )\t los+ _!  
significance4 ,"s ( ^! subdivisions *>g$
 9 a c]ta9 way or ) neutraliz$ *>ge     
exhibit ! prop]ties ( s-call$ matt]4    
,scatt]+ ( ,alpha ,p>ticles  ,?is       
conception ( ! atom w\ld d\btless fail (
 mu* support 7 x n = c]ta9 exp]im5tal   
facts :i* l5d great weight to x4 ,c]ta9 
suppositions c be bas$ on ?is !ory      
ma!matically reason$ out & te/$ by      
exp]im5t4 ,pr$ictions ?us bas$ on       
ma!matical reason+ & aft]w>d confirm$ by
 exp]im5t give a v conv9c+ impression t 

tru? lies at ! bottom4  ,! fir/ ( ^!    
exp]im5tal pro(s comes "u ! head ( :at  
is kn[n z ! scatt]+ ( ! alpha p>ticles1 
a ph5om5on :i*1 :5 fir/ obs]v$1 prov$   
h>d to expla94 ,if an alpha p>ticle 9   
its escape f ! p>5t atom %\ld come )9 ! 
influ5ce ( ! suppos$ out] electrical    
field ( "s o!r atom1 x %\ld be deflect$ 
f its c\rse &1 ! int5sity ( ! two *>ges 
be+ kn[n1 ! angle ( deflection c\ld be  
calculat$4 ,= in/ance1 if x came to :at 
might be call$ a head-on collision ) !  
positive c5tral nucleus ( ano!r atom1 x 
w\ld recoil if x 7 itself ( less] mass1 
or w\ld propel ! o!r =w>d if t 7 !      
light]4  ,! exp]im5t is c>ri$ out by    
plac+ a ?9 metal foil ov] a radio-active
 body1 z radium ,c1 :i* expels alpha    
p>ticles ) a high velocity1 & c\nt+ !   
numb] ( alpha p>ticles :i* are scatt]$  
?r\gh an angle great] ?an #ij & s recoil
 t[>d _! s\rce4 ,?is has be5 done by a  
numb] ( inve/igators & x has be5 f\nd t 
! angle ( scatt]+ & ! numb] ( recoil    
p>ticles dep5d ^u ! atomic weight ( !   

metal us$ z foil4 ,= example1 if gold is
 us$1 ! numb] ( recoil atoms is "o 9    
some?+ less ?an #h1jjj4  ,tak+ ! atomic 
weight ( gold into consid]ation1 ,ru!r=d
 calculat$ ma!matically t ?is 0 ab\t !  
numb] :i* %\ld be driv5 backw>d4 ,b he  
w5t fur!r & calculat$ also ! numb] :i*  
%\ld be return$ by alum9um1 :i* has an  
atomic weight ( only ab\t "o-sev5? t (  
gold4 ,two inve/igators det]m9$         
exp]im5tally ! numb] = alum9um & _!     
results agre$ ) ,ru!r=d's calculations4 
,! metals f alum9um to gold h be5 exam9$
 9 ?is way4 ,! numb] ( recoil p>ticles  
increases ) ! atomic weight ( ! metal4  
,comp>+ exp]im5t ) !ory1 ! c5tral *>ge 9
 an atom corresponds to ab\t "o-half !  
atomic weight multipli$ by ! *>ge on an 
electron1 or1 z x is express$1 #a_/b    
,ae4  ,!re is only "o light] atom ?an   
helium1 namely1 hydrog51 :i* has a mass 
only "o-f\r? z great4 ,:5 alpha p>ticles
 are dis*>g$ into hydrog51 a few ( !    
latt] atoms are f\nd to be propell$ to a
 di/ance f\r times z great z t rea*$ by 

! alpha p>ticles4   ,/opp+ ,p[] (       
,sub/ances  ,p>allel ) ! exp]im5ts      
m5tion$1 !re is :at is call$ ! /opp+ p[]
 ( sub/ances4 ,?is means ! dep? or      
?ickness ( a sub/ance necess>y to put a 
/op to ! c\rse ( ! alpha p>ticles4 ,?is 
gives ! range ( ! alpha p>ticles 9 su*  
sub/ances & is connect$ 9 a simple way )
 ! atomic weight1 t is1 x is aga9 fix$  
by ! mass ( ! oppos+ atom4 ,?is /opp+   
p[] ( an atom = an alpha p>ticle is     
approximately proportional to ! squ>e   
root ( its atomic weight4  ,consid]+    
gases1 = in/ance1 if ! range 9 hydrog5  
be #a1 !n ! range 9 oxyg51 ! atomic     
weight ( :i* is #af1 is only            
7#a_/af7a_/b or #a_/d4 ,g5]ally 9 ! case
 ( metals ! weight ( matt] p] unit area 
requir$ to /op ! alpha p>ticle is f\nd  
to v>y accord+ to ! squ>e root ( !      
atomic weight ( ! metal tak54           
,,*apt] ,,vi  ,,radio-,,activity ,,&    
,,*emical ,,!ory   ,influ5ce ^u ,*emical
 ,!ory  ,x c easily be se5 t !          
revelations ( radio-activity mu/ h a    

f>-rea*+ effect ^u *emical !ory1 ?r[+   
light ^u1 & s br++ ne>]1 ! solution ( "s
 ( ! problems :i* h be5 long discuss$   
)\t arriv+ at any satisfactory solution4
 ,! s-call$ electro-*emical nature ( !  
elem5ts w c]ta9ly be made mu* cle>]4 ,! 
*anges 9 val5ce %\ld become intelligible
 & val5ce itself %\ld be expla9$4 ,a    
full] und]/&+ ( ! ionization (          
electrolytes also becomes possible4 ,z  
^! matt]s are debatable & ! details are 
/ill unsettl$1 x is sc>cely appropriate 
to give "h ! hypo!ses 9 detail or to    
ent] into any discussion ( !m4 ,b !     
promise ( solution 9 accord ) ! facts is
 enc\rag+4   ,! ,p]iodic ,sy/em  ,su*   
progress has be5 made1 h[ev]1 9 reg>d to
 a bett] und]/&+ ( ! ,p]iodic ,sy/em t !
 new facts & _! int]pretation may well  
be giv54 ,no reliable clue to ! mean+ ( 
?is sy/em & ! true relation%ip betwe5 ! 
elem5ts _h be5 f\nd up to ! "t :5 new   
light 0 ?r[n ^u x by ! discov]ies (     
radio-activity4 ,! und]ly+ pr9ciple 0   
unkn[n & ev5 ! /atem5t ( :at 0 sometimes

 errone\sly call$ ! ,p]iodic ,law 0     
manife/ly incorrect & its t]ms 7 ignor$4
   ,basis ( ! ,p]iodic ,sy/em  ,! ord9>y
 /atem5t ( ! fundam5tal pr9ciple ( !    
,p]iodic ,sy/em has be5 t ! prop]ties ( 
! elem5ts 7 p]iodic functions ( ! atomic
 weights1 & t :5 ! elem5ts 7 arrang$ 9 !
 ord] ( _! atomic weights !y fell into a
 natural s]ies1 tak+ _! places 9 ! prop]
 relat$ gr\ps4  ,9 accept+ ?is1 !       
int]pretation ( function 0 bo?          
unma!matical & vague1 & ! ord] ( !      
atomic weights 0 n /rictly adh]$ to b   
unhesitat+ly ab&on$ to =ce ! gr\p       
relation%ip4 ,:]ev] consid]ation ( !    
atomic weight w\ld h plac$ an elem5t out
 ( ! gr\p+ ) o!r elem5ts to :i* x 0     
cle>ly relat$ 9 physical & *emical      
prop]ties1 ! guidance ( ^! prop]ties 0  
accept$ & t ( ! atomic weights          
disreg>d$4 ,su* %ift+s are not$ 9 !     
cases ( tellurium & iod9e2 cobalt &     
nickel2 argon & potassium4 ,x 0 mo/     
helpful t1 foll[+ ! ord] ( atomic       
weights1 ! majority ( ! elem5ts fell    

naturally into _! places4 ,o!rwise !    
g5]alization kn[n z ! ,p]iodic ,sy/em   
might h rema9$ = a long "t undiscov]$ & 
! progress ( *emi/ry w\ld h be5 greatly 
ret>d$4   ,influ5ce ( ,positive ,nucleus
  ,x is evid5t t ! ord] ( ! elem5ts is  
det]m9$ by some?+ else ?an _! atomic    
weights4 ,f ! kn[n facts (              
radio-activity x w\ld seem t ?is det]m9+
 factor is ! positive nucleus4 ,& ?is   
nucleus also det]m9es ! mass or weight (
 ! atom4 ,tak+ ! elem5ts 9 _! ord] 9 !  
,p]iodic ,s]ies & numb]+ ! positions    
held by !m 9 ?is s]ies z #a1 #b1 #c1    
etc41 we get ! position numb] or :at is 
call$ ! atomic numb]4 ,?is designates ! 
ord] or position ( ! elem5t 9 ! s]ies4  
,we mu/ le>n t ?is numb] m>ks a position
 r ?an a s+le elem5t1 a /atem5t :i* w be
 expla9$ lat]4   ,det]m9ation ( !       
,atomic ,numb]  ,s9ce ! atomic weight is
 unreliable z a means ( settl+ !        
position ( an elem5t 9 ! s]ies & s fix+ 
its atomic numb]1 h[ is ?is numb] to be 
det]m9$8 ,( c\rse1 "o answ] to ?is "q is

 t we may rely ^u a consid]ation ( !    
g5]al prop]ties1 z has be5 done 9 ! pa/4
 ,=tunately1 o!r me?ods h be5 f\nd by   
:i* ?is may be confirm$4 ,= in/ance1 !  
/opp+ & scatt]+ p[] ( ! elem5t = alpha  
p>ticles has be5 sugge/$ & successfully 
us$4   ,use ( ,x-,ray ,spectra  ,a mo/  
int]e/+ me?od is due to ,moseley's      
obs]vations ^u ! ,x-ray spectra ( !     
v>i\s elem5ts4 ,x has be5 f\nd t        
cry/als1 su* z ^? ( qu>tz1 h ! p[] (    
reflect+ & def9+ ! ,x rays4 ,! spectra  
giv5 by ^! rays c be photograph$ & !    
wave l5g?s measur$4 ,^! ,x rays are     
emitt$ by v>i\s sub/ances "u bomb>dm5t  
by ! ca?ode rays 7negative electrons7 & 
h great int5sity & v m9ute wave l5g?s4  
,moseley made use ( v>i\s metals z      
anti-ca?odes = ! production ( ^! rays4  
,^! metals rang$ f calcium to z9c 9 !   
,p]iodic ,sy/em4 ,9 ea* case he obs]v$ t
 two *>act]i/ic types ( ,x rays (       
def9ite int5sity & diff]5t wave l5g?s 7 
emitt$4 ,f ! frequ5cy ( ^! waves !re is 
d$uc$ a simple relation connect$ ) a    

fundam5tal quantity :i* increases 9     
units f "o elem5t to ! next4 ,?is is due
 to ! *>ge ( ! positive c5tral nucleus4 
,! numb] f\nd 9 ?is way is "o less ?an !
 atomic numb]4 ,?us ! numb] = calcium is
 #ai in/ead ( #bj & t = z9c is #bi      
in/ead ( #cj4 ,s1 by add+ #a to ! numb] 
f\nd ! atomic numb] is obta9$4  ,!      
atomic weight c usually be foll[$ 9 fix+
 ! atomic numb]1 b :]e d\bt exi/s !     
me?od j giv5 c be resort$ to4 ,?us d\bt 
arises 9 ! case ( iron & nickel &       
cobalt4 ,?is w\ld be ! ord] accord+ to !
 atomic weights4 ,! ,x-ray me?od gives !
 ord] z iron1 cobalt1 & nickel1 & ?is is
 ! accept$ ord] 9 ! ,p]iodic ,sy/em4    
,*anges ,caus$ by ,ray ,emission  ,on   
/udy+ ! prop]ties ( ! elem5ts 9 a       
trans=mation s]ies 9 connection ) ! ray 
emission :i* produc$ !m1 x 0 se5 t ^!   
prop]ties 7 det]m9$ 9 ea* case by !     
nature ( ! ray emitt$ f ! prec$+        
trans=mation product or p>5t elem5t4    
,atomic ,weight ,losses  ,ea* alpha     
p>ticle emitt$ means a loss ( #d 9 !    

atomic weight4 ,?is is ! mass ( a helium
 atom4 ,?us f uranium ) an atomic weight
 ( #bch to radium !re is a loss ( ?ree  
alpha p>ticles4 ,!re=e1 #ab mu/ be      
subtract$ f #bch1 leav+ #bbf1 :i* agrees
 closely ) ! atomic weight ( radium z   
actually det]m9$ by ! ord9>y me?ods4    
,uranium ,x#a1 !n1 w\ld h an atomic     
weight ( #bcd & t ( ionium w\ld be #bcj4
 ,! o!r int]m$iate elem5ts1 ^: =mation  
is due to ! loss ( beta p>ticles only1  
%[ no decrease 9 atomic weight4   ,lead 
! ,end ,product  ,f uranium to lead !re 
is a loss ( #h alpha p>ticles1 or #cb   
units 9 atomic weight4 ,?is w\ld give = 
! f9al product an atomic weight ( #bjf4 
,! atomic weight ( lead is #bjg4ag4 ,x  
is n at all c]ta9 t ! f9al product ( ?is
 s]ies is ord9>y lead4 ,! facts are su* 
t !y w\ld lead "o to ?9k t x is n4 ,x is
 kn[n only t ! end product w\ld probably
 be "s elem5t closely resembl+ lead     
*emically & h5ce difficult or impossible
 to sep>ate f x4 ,sev]al accurate       
det]m9ations ( lead com+ f uranium      

m9]als1 :i* always c>ry ?is elem5t & 9  
an approximately def9ite ratio to !     
am\nt ( uranium pres5t1 %[ atomic       
weights ( #bjf4dj2 #bjf4cf2 & #bjf4ed4  
,ev5 ! mo/ rigid me?ods ( purification  
fail to *ange ^! results4 ,! lead 9 ^!  
m9]als might !re=e be consid]$ z com+ 9 
! ma9 f ! dis9tegration ( ! uranium atom
 &1 ?\gh *emically resembl+ lead1 z be+ 
9 reality a diff]5t elem5t ) diff]5t    
atomic weight4  ,fur!rmore1 9 ! ?orium  
s]ies #f alpha p>ticles are lo/ be=e    
rea*+ ! end product1 :i* aga9 is p]haps 
! *emical analogue ( lead4 ,! atomic    
weight "h %\ld be #bcb less #bd1 or     
#bjh4 ,det]m9ations ( ! atomic weight ( 
lead f ?orite1 a ?orium m9]al ne>ly free
 f uranium1 gave #bjh4d4  ,! end product
 ( ! act9ium s]ies is also an elem5t    
resembl+ lead1 b bo? ! beg9n+ & end+ (  
?is s]ies are /ill 9 obscurity4         
,*anges ( ,position 9 ! ,p]iodic ,sy/em 
,! loss ( #d units 9 ! atomic weight (  
an elem5t on ! expulsion ( an alpha     
p>ticle is accompani$ by a *ange (      

*emical prop]ties :i* removes ! new     
elem5t two gr\ps t[>d ! positive side 9 
! ,p]iodic ,sy/em4  ,?us ionium is s    
closely relat$ to ?orium & s resembles x
 *emically t x is prop]ly class$ along )
 ?orium z a quadrival5t elem5t 9 ! f\r? 
gr\p4 ,ionium expels an alpha p>ticle & 
becomes radium1 :i* is a bival5t elem5t 
resembl+ b>ium belong+ to ! second gr\p4
 ,radium !n expels an alpha p>ticle &   
becomes ! gas1 radium emanation1 :i* is 
an analogue ( argon & belongs to ! z]o  
gr\p4 ,o!r in/ances might be cit$ :i* g 
to %[ t 9 all cases ! loss ( an alpha   
p>ticle makes a *ange ( two places t[>d 
! left or positive side ( ! ,sy/em4     
,*anges f ,loss ( ,beta ,p>ticles  ,!   
loss ( a beta p>ticle causes no *ange 9 
! atomic weight b does cause a %ift =   
ea* beta p>ticle ( "o gr\p t[>d ! "r or 
negative side ( ! ,sy/em4 ,two su*      
losses1 !n1 w c\nt]balance ! loss ( an  
alpha p>ticle & br+ ! new elem5t back to
 ! gr\p orig9ally occupi$ by its        
prog5itor4 ,?us uranium 9 ! six? gr\p   

loses an alpha p>ticle & ! product      
,,ux#a falls 9 ! f\r? gr\p4 ,"o beta    
p>ticle is !n lo/ & ,,ux#b belong+ to ! 
fif? gr\p is =m$4 ,) ! loss ( "o m beta 
p>ticle ! new elem5t returns to ! six?  
gr\p f :i* ! trans=mation began4  ,!    
table on page #dh1 z adapt$ f ,soddy1   
af=ds a g5]al view ( ^! *anges4         
,isotopes  ,an exam9ation ( ! table w %[
 a numb] ( diff]5t elem5ts fall+ 9 !    
same position 9 a gr\p ( ! ,p]iodic     
,sy/em irrespective ( _! atomic weights4
 ,^! are *emically insep>able s f> z !  
pres5t limitations ( *emical analysis   
are conc]n$4 ,ev5 ! spectra ( ^! elem5ts
 seem to be id5tical s f> z kn[n4 ,?is  
id5tity ext5ds to mo/ ( ! physical      
prop]ties1 b ?is dem&s mu* fur!r        
inve/igation4 ,= ?is new ph5om5on ,soddy
 has sugge/$ ! ^w isotope = ! elem5t &  
isotopic = ! prop]ty1 & ^! names h come 
into g5]al use4      ,illu/ration3      
,,radio-,,active ,,elem5ts ,,f ,,uranium
 ,,& ,,?orium     ,,plac$ ,,9 ,,!       
,,p]iodic ,,sy/ems            ,adapt$ f 

,soddy  ,manife/ly1 we h come across a  
ph5om5on "h :i* q elim9ates ! atomic    
weight z a det]m9+ factor z to position 
9 ! ,p]iodic or ,natural ,sy/em or ( !  
elem5tal prop]ties 9 g5]al4 ,all ( !    
prop]ties ( ! bodies :i* we call        
elem5ts1 & consequ5tly ( _! comp\nds &  
h5ce ( matt] 9 g5]al1 seem to dep5d ^u !
 balance ma9ta9$ betwe5 ! *>ges (       
negative & positive electricity :i*1    
accord+ to ,ru!r=d's !ory1 g to make up 
! atom4  ,x is evid5t t any /udy (      
*emical ph5om5a & *emical !ory is q     
incomplete )\t a /udy ( radio-activity &
 ! trans=mations :i* x produces4        
,radio-activity 9 ,nature  ,9 conclud+  
?is outl9e ( ! ma9 facts (              
radio-activity1 x is ( int]e/ to discuss
 briefly ! pres5ce ( radio-active       
mat]ial on ?is planet & 9 ! />s4 ,facts 
en\gh h be5 ga!r$ to %[ ! probable      
univ]sality ( ?is ph5om5on (            
radio-activity4 ,:e!r ?is means solely !
 dis9tegration ( ! uranium & ?orium     
atoms1 or :e!r o!r elem5ts are also     

trans=m$ "u ! int5sity ( ! ag5cies at "w
 9 ! univ]se1 is ( c\rse a "q z yet     
unsolv$4   ,radio-active ,products 9 !  
,e>?'s ,cru/  ,! pres5ce ( uranium &    
?orium widely di/ribut$ ?r\gh\t ! cru/ (
 ! e>? w\ld lead to ! conclusion t _!   
dis9tegration products w\ld be f\nd !re 
also4 ,v>i\s rocks ( igne\s orig9 h be5 
exam9$ reveal+ f #d4gh  #aj-ab to #j4ca 
#aj-ab grams ( radium p] gram ( ! rock4 
,aque\s rocks h %[n a less] am\nt1 rang+
 f #b4ib  #aj-ab to #j4hf  #aj-ab grams4
 ,z ! soil is =m$ by ! decomposition (  
^! rocks1 radium is pres5t 9 v>y+ am\nts
 9 all k9ds ( soil4   ,pres5ce 9 ,air & 
,soil ,wat]s  ,z radium is trans=m$ into
 ! gase\s emanation1 ?is w escape :]ev] 
! soil is n enclos$4 ,= in/ance1 a l>g] 
am\nt ( radio-activity is f\nd 9 ! soil 
( caves & cell>s ?an 9 op5 soils4 ,if an
 iron pipe is sunk into a soil & ! air (
 ! soil suck$ up into a l>ge            
electroscope1 ! latt] in/rum5t w %[ !   
effect ( ! rays emitt$ & w measure !    
degree ( activity4 ,also ! int]ior ( !  

pipe w receive a deposit ( !            
radio-active mat]ial & w %[ appreciable 
radio-activity aft] be+ remov$ f ! soil4
  ,?is radium emanation is dissolv$ 9 ! 
soil wat]s1 wells1 spr+s1 & riv]s1 r5d]+
 !m m or less radio-active1 & sometimes 
! muddy deposit at ! bottom ( a spr+ %[s
 decid$ radio-activity4  ,! emanation   
also escapes into ! air s t _m          
obs]vations made 9 v>i\s places %[ t !  
radium emanation is ev]y:]e pres5t 9 !  
atmosph]e4 ,nei!r summ] nor w9t] seems  
to affect ?is emanation1 & x ext5ds     
c]ta9ly to a height ( two or ?ree miles4
 ,ra91 fall+ ?r\gh ! air1 dissolves "s (
 ! emanation1 s t x may be f\nd 9       
fre%ly-fall5 ra9 wat] & also 9          
fre%ly-fall5 sn[4 ,radio-active deposits
 are f\nd ^u electrically *>g$ wires    
expos$ ne> ! e>?'s surface4  ,z helium  
is ! result+ product ( ! alpha p>ticles 
emitt$ by ! emanation & o!r radio-active
 bodies1 x is f\nd 9 ! soil air1 soil   
wat]s1 & atmosph]e4  ,av]age measurem5ts
 ( ! radio-activity ( ! atmosph]e h l$  

to ! calculation t ab\t "o gram ( radium
 p] squ>e kilomet] ( ! e>?'s surface is 
requisite to keep up ! supply ( !       
emanation4  ,a numb] ( e/imates h be5   
giv5 z to ! heat produc$ by !           
radio-active trans=mations go+ on 9 !   
mat]ial ( ?is planet4 ,actual data are  
sc>ce & m]e assumptions unsatisfactory1 
s little t is wor? :ile c be d$uc$4 ,x  
is possible t ?is s\rce ( heat may h an 
appreciable effect ^u or s]ve to balance
 ! e>?'s rate ( cool+4   ,cosmical      
,radio-activity  ,meteorites ( iron com+
 f o!r cele/ial bodies h n %[n ! pres5ce
 ( radium4 ,a]olites or /one meteorites 
h be5 f\nd to conta9 z mu* z simil>     
t]re/rial rock4 ,s9ce ! sun conta9s     
helium & "s />s %[ its pres5ce z        
pr$om9at+1 ?is sugge/s ! pres5ce (      
radio-active matt] 9 ^! bodies4 ,9      
addition1 ! spectral l9es ( uranium1    
radium1 & ! radium emanation h be5      
report$ z be+ f\nd 9 ! sun's spectrum & 
also 9 ! new />1 ,nova ,gem9orum #b4 ,^!
 obs]vations await fur!r inve/igation & 

confirmation4 ,s f> z ! sun's *romosph]e
 is conc]n$1 ! possible am\nt ( radium  
pres5t w\ld seem to be v small4 ,if ?is 
is true1 radio-active processes c\ld h  
little to d ) ! sun's heat4 ,! /atem5t  
is made by ,ru!r=d t indirect evid5ce   
obta9$ f ! /udy ( ! aurora sugge/s t !  
sun emits rays simil> 9 type to ! alpha 
& beta rays4 ,su* rays w\ld be absorb$1 
& ! gamma rays likewise1 9 pass+ ?r\gh !
 e>?'s atmosph]e & s escape ord9>y      
obs]vation4 ,all ( ?is is b fur!r       
evid5ce ( ! unity ( matt] & ( =ces 9 !  
univ]se4     ,,index     ,act9ium1      
discov]y (1 #f    ,activity1 induc$1 #ag
    ,alpha p>ticles1 effect ( loss on   
,atomic ,weight1 #de     electrical *>ge
 (1 #bf     =m helium1 #bg     nature (1
 #be     p5etrat+ p[] (1 #ci            
position ( elem5t *ang$ by its loss1 #df
     recoil1 #ci     scatt]+ (1 #ch     
solid1 #bf    ,atom1 con/itution (1 #cf 
,kelv9's1 #cg     models (1 #cg         
,ru!r=d's1 #cg    ,atomic numb]1        
det]m9ation (1 #dc     ,becqu]el's      

exp]im5ts1 #b    ,beta p>ticles1 *ange 9
 position ( elem5t by loss (1 #dg       
,*alcolite1 natural & artificial1 #d    
,con/ants1 table (1 #ca    ,curie unit1 
#bb     ,dis9tegration ( ! elem5t1 #be  
,dis9tegration s]ies1 #bd               
,dis9tegration !ory1 #ce                
,electroscope1 #ab    ,equilibrium      
s]ies1 #bb     ,helium1 *>act]i/ics (1  
#cj     discov]y (1 #bi     ,ionium1    
discov]y (1 #f    ,ionization1          
application ( electric field to1 #aj    
exp]im5tal confirmation1 #i             
,ionization ( gases1 #g     !ory (1 #h  
,ions1 size & nature (1 #aj             
,isotopes1 #dg     ,lead1 atomic weight 
v>ies ) s\rce1 #de     radio-active1 #f 
! end product1 #de    ,life-p]iods (    
radio-active bodies1 #ba     ,p]iodic   
sy/em1 #da     basis (1 #db             
,polonium1 discov]y (1 #d    ,positive  
nucleus1 influ5ce (1 #dc    ,potassium1 
radio-activity (1 #c     ,radiations1   
action on phosphoresc5t bodies1 #ac     
action on photographic plates1 #aa      

dis*>ge electrifi$ bodies1 #ab          
magnetic deflection (1 #ad              
measurem5ts (1 #ae     p5etrat+ p[] (1  
#ac1 #ae    ,radio-active bodies1       
elem5tal nature (1 #bj     exam9ation (1
 #bj     life p]iods (1 #ba             
,radio-activity1 an atomic prop]ty1 #c  
cosmical1 #ea     influ5ce on *emical   
!ory1 #da     products 9 atmosph]e1 #ea 
products 9 e>?'s cru/1 #ej     products 
9 soil wat]s1 #ej    ,radium1 action on 
organic matt]1 etc41 #cc     am\nt 9    
pit*bl5de1 #e     discov]y (1 #e        
emanation1 #bb     en]gy evolv$ by1 #cd 
prop]ties (1 #e1 #cb    ,rays1 alpha1   
#ae1 #af1 #bf     beta1 #ae1 #af        
gamma1 #ae1 #af     id5tification (1    
#af1 #be     magnetic deflection (1 #ad 
photograph+ track (1 #aj     types (1   
#ad    ,rubidium1 radio-activity (1 #c  
,sp9?>iscope1 #ac    ,/opp+ p[] (       
sub/ances1 #ci     ,?orium ,x1 discov]y 
(1 #ah1 #ba     ,uranium atom1          
dis9tegration (1 #cf    ,uranium m9]als1
 radio-activity (1 #c    ,uranium ,x1   

discov]y (1 #ag1 #ba1 #bc     ,x-ray    
spectra1 #dd     ,z9c sulphide scre51   
#ac     ,,transcrib]',s ,,notes   #a4   
,passages 9 italics are surr\nd$ by     
und]scores4  #b4 ,images h be5 mov$ f ! 
middle ( a p>agraph to ! close/ p>agraph
 break4  #c4 ,! orig9al text includes   
c]ta9 ,greek alphabets4 ,= ?is text     
v]sion alpha1 beta1 gamma indicate fir/ 
?ree lett]s ( ,greek alphabet           
respectively4  #d4 ,9 ?is v]sion1 !     
numb] foll[+ c>at "*  is to be int]pret$
 z foll[s4 ,! expression #aj-b means    
multiply+ by #j4ja2 #ajaj means         
multiply+ by #aj1jjj1jjj1jjj4  #e4 ,9   
?is v]sion1 ! subscript$ text has be5   
replac$ by an und]l9e "*  foll[$ by !   
same ) curly braces  & 4 ,= example1    
,x#a indicates ,x ) subscript #a4  #f4  
,! fractions are indicat$ ) ! help (    
=w>d "* _/4 ,= example1 #a_/d indicates 
"o-f\r?4  #g4 ,o!r ?an ! *anges li/$    
above1 ! orig9al text has be5 reproduc$ 
z su*4