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An English translation by Tait had recently appeared [Phil. Mag. 33: 485-512] of Helmholtz, H. 1858. Ueber Integrale der hydrodynamischen Gleichungen, welche den Wirbelbewegungen entsprechen. Journal für die reine und angewandte Mathematik 55: 25-55. William Thomson also makes mention of papers from Rankine (1849-50) on "Molecular Vortices". 2 Kragh, H. 2012. Niels Bohr and the Quantum Atom, Oxford University Press, Oxford. 3 Heilbron, J. L. 1981. Historical Studies in the Theory of Atomic Structure, Arno Press, New York. 5 C+( ,#6*'( #07( X#%410&$ H ( 7&'4$*C&'( JK( JK( L"1/'10R'( +18."28%( 7&61.*10( .1( b#QB&%%*#0( &%&4.$17+0#/*4'(#07(."&(/&4"#0*4#%(&."&$K( b1$&16&$9( b#QB&%%R'( %&E#4+( #'( ."&( 6*'*10#$+( 21807&$( 12( ."&( !#6&07*'"( h#C1$#.1$+(*0(!#/C$*7E&(*'(10&(12(."&(/#0+(."$'(."#.(C*07(."&(."$&&(/#*0(#4.1$'( *0( ."&( '.1$+( ."#.( 21%%1B'K( ( L"*'( *'( ."&( -%#4&( B"&$&( L"1/'10( B#'( # 1*0.&7( #'( 7*$&4.1$( *0( G;;H9( B"&$&( N8."&$21$7( B1$F&7( # '( L"1/'10R'( 2*$'.( $&'&#$4"( '.87&0.( 2$1/(G;>](.1(G;>;9(#07(B"&$&()1"$('.1 &7(16&$(*0(G>GG(C&21$&(/16*0E(10(.1(g1*0( N8."&$21$7(#.(."&(50*6&$'*.+(12(b#04"&'.&$K((L"&$&(*'(#0(1%7(#7#E&( . "#.(/1'.(%*0&'(12( $&'&#$4"( *0( /17&$0( -"+'*4'9( B"&0( .$#4&7( C#4F( 2#$( &018E"9( B*%%( &6&0.8#%%+( %( .1( J#/&'( !%&$F( b#QB&%%9( #07( ."*'( *'( 01( %&''( .$8&( B"&0( 7&%6*0E( *0.1( ."&( 1$*E*0'( 12( /&4"#0*4#%(/17&%'(12(."&(#.1/K( , ( 4 Davis, E. A. and Falconer, I. J. 1997. J. J. Thomson and the Discovery of the Electron, Taylor & Francis, London. 6 2, The,mechanical,atoms,of,J.,J.,Thomson( ( 2.1, Rings,of,Saturn,and,ethereal,vortices( ( L"&(*0.$1784.*10(.1(b#QB&%%R'(G;]T(&''#+9(S:0(."&(@.#C*%*.+(12(."&(b1.*10(12( @#.8$0R'( N*0E'9S( 410.#*0'( #( 4104*'&( '.#.&/&0.( 12( ."&( 4&0.$#%( ."&/&( 12( "*'( #0#%+'*'9( C8.(#%'1(."#.(12(#0(&0.*$&($&'&#$4"(-$1E$#/(+&.(.1(41/&(10(/&4"#0*4#%(/17&%'(12(."&( #.1/K( ( SY#6*0E( 21807( #( -#$.*48%#$( '1%8.*10( 12( ."&( &D8#.*10'( 12( /1.*10( 12( #0+( /#.&$*#%( '+'.&/9( .1( 7&.&$/*0&( B"&."&$( #( '%*E".( 7*'.8$C#04&( 12( ."&( /1.*10( *07*4#.&7( C+( ."&( '1%8.*10( B18%7( 4#8'&(#( '/#%%( -&$*17*4( 6#$*#.*109( 1$( #( .1.#%( 7&$#0E&/&0.(12(."&(/1.*10KS(kb#QB&%%(G;]>9(-K(]l( ( L"&( -$*Z&( 41//* &&( 21$( ."#.( +&#$( "#7( #'F&7( *2( ."&( %10E?.&$/( '.#C*%*.+( 12( @#.8$0R'( $*0E'(418%7(C&(&Q-%#*0&7(10(7+0#/*4#%(-$*04*-%&'9(807&$(."&(#''8/ *10(."&+(B&$&( &*."&$('1%*79(%*D8*79(1$(/#7&(8-(2$1/(-#$.*48%#.&(/# &$K((V0(#0'B&$(.1(."*'(4"#%%&0E&9( b#QB&%%('*/8%.#0&18'%+(C$18E".( .1(C&#$(#( 08/C&$(12(/#."&/#.*4#%( .&4"0*D8&'(\*0( -#$.*48%#$9( X18$*&$( #0#%+'*'( #07( h#E$#0E*#0( /&4"#0*4'_( .1( 2*$'.( '"1B( ."#.( #( 80*21$/%+( '1%*7( $*0E( B18%7( C&( &*-"0,!"//*( 1-+#"5/'9 ] ( #07( ."#.( #( %*D8*7( $*0E( /8'.( 8%.*/#.&%+(C$&#F(#-#$.(*0.1(7*'4100&4.&7(7$1-%&.'K( ( L"&($&/#*0*0E(-1''*C*%*.+(B#'(21$(."&($*0E'(.1(C&(41/-$*'&7(12(*07&-&07&0.( -#$.*4%&'(\B"&."&$('1%*7(1$(%*D8*7_9("(/16*0E(807&$(."&(E$#6*.#.*10#%(*02%8&04&(12( ."&( 4&0.$#%( /#''9( #'( B&%%( #'( ."#.( 12( #%%( ."&( 1."&$( 1$C*.*0E( -#$.*4%&'K( ( b#QB&%%( # $1Q*/#.&7(#('*0E%&(-%#0&.#$+($*0E(#'(#(41%%&4.*10(12(-1*0.(/#''&'(7*'.$*C8 .&7(#.( &D8#%?#0E%&( *0.&$6#%'( #$1807( #( 4*$4%&9( 7&$*6&7( ."&( &D8#.*10'( 12( /1.*10( 21$( .B1( /#''&'( *0( '.#C%&( 1$C*.9( ."&0( '.&-B*'&( %&.( ."&( 08/C &$( 12( '#.&%%*.&'( E$1B( 80.*%( #$C*.$#$*%+( %#$E&K((5-10( 7&.&$/*0*0E( ."&( 4107*.*10'( 21$( '.+?'.#.&( /1.*109( "&( 410'*7&$&7(."&(&22&4.(12(#0+('/#%%(7&6*#.*10(12(."&(-#$.*4%&'(2$1/(."&*$(1$C*.'9(*0(."&( 5 There would be an insufficient restoring force if the centers of mass for the uniform ring and the planet ever deviated from equilibrium, eventually leading the ring and planet to crash into each other. The only exception was most unlikely: an otherwise uniform ring would require an additional point mass located at its outer edge, equal to 0.82 of the mass of the total ring. [Maxwell 1859, p. 55] 7 $#7*#%(#07(.#0E &0.*#%(7*$&4.*10'9(#'(B&%%(#'(-&$-&07*48%#$(.1(."&(-%# 0&(12($1.#.*10K((V2( ."&( /1. *10( 12( ."&( -#$.*4%&'( B&$&( .1( C&( -&$/#0&0.9( ."&( '1%8.*10'( .1( ."&'&( '&.'( 12( 7*22&$&0.*#%(&D8#.*10'(B18%7("#6&(.1(#%%(C&('*08'1*7#%(\."&(-#$.*4%&'(B18%7(1'4*%%#. &( #C18.(."&*$( &D8*%*C$*8/(-1'*.*10'_j(&Q-10&0.*#%( '1%8.*10'( 41$$&'-107&7(.1( ."&($*0E( C$&#F*0E(#-#$.K((L"*'(-%#4&7(C#'*4(410'. $#*0.'(10(."&(-$1-&$.*&'(12(."&('+'.&/(^(/1'.( 01.#C%+9(."&(/#''(12(."&(4&0.$#%(C17+(B18%7("#6&(.1(C&('8C'.#0.*#%%+(%#$E&$(."#0(."&( '8/(12(."&(1$C*.*0E(/#''&'K(kb#QB&%%(G;]>9(-K(W]l( ( L"&(*02%8&04&(12(b#QB&%%(*'($*%+(# #$&0.(*0(L"1/'10R'(1B0(G;;W(A7#/'( 3$*Z&(&''#+K((L"*'(.*/&9(."&(41//* &&("#7(4#%%&7(21$(#(SE&0&$#%(*06&'.*E#.*10(12(."&( #4.*10(8-10( "( 1."&$(12( .B1( 4%1'&7(61$.*4&'( *0( #(-&$2&4.( *041/-$&''*C%&(2%8*79S(#( .1-*4( ."#.( B#'( 12( 48$$&0.( *0.&$&'.( .1( /#."&/#.*4#%( -"+'*4*'.'9( - # $.*48%#$%+( '*04&( b#QB&%%( "#7( 7&'4$*C&7( X#$#7#+R'( /,-'+( %6( 6%)!'( *0( .&$/'( 12( 61$.*4&'( *0( #0( &%&4.$1/#E0&.*4(/&7*8/K [ ((L"&(2807#/&0.#%('*/-%*4*.+(12(i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knl(L"&(*06&'.*E#.*10(n( *061%6&7(%10E(#07(41/-%*4#.&7(/#."&/#.*4#%(#0#%+'*'(#07(.11F(#(%10E(.*/&K( (V.( +*&%7&79( "1B&6&$9( '1/&( *0.&$&'.*0E( $&'8%.'( #07( *7&#'( B"*4"( V( #2.&$B#$7'( 21807(6#%8#C%&(*0(4100&4.*10(B*."(."&(."&1$+(12(."&('.$84.8$&(12(."&(#.1/nS( kL"1/'10(G>=[9(-K(>H?]l( ( ( L"&(2*$'.(.B1(-#$.'(12(L"1/'10R'(&''#+(7&#%.(B*."(."&(/#."&/#.*4'(7&'4$*C*0E( #('*0E%&(61$.&Q(*0(#0(*7&#%(2%8*79(#07(."&0(.B1(61$.*4&'('&-# $#.&7(C+(#(7*'.#04&(%#$E&( 41/-#$&7( .1( ."&*$( $#7**9( B"*4"( #%10&( /*E".( "#6&( C&&0( '822*4*&0.( .1( '#.*'2+( ."&( 6 Maxwell 1861, p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kL"1/'10(G;;=#9(-K(G<T?;l( ( )&+107( /#."&/#.*4#%( &Q-&7*&04+9( L"1/'10R'( 4"1*4&( .1( B1$F( B*."( '+//&.$*4#%%+(7*'.$*C8.&7(61$.*4&'(418%7(C&(-"+'*4#%%+(/1.*6#. &7(B*."(#0(#0#%1E+(.1( ."&('.#.*4(#$$#0E&/&0.'(12(2%1#.*0E(/#E0&.'(807&$(."&(*02%8&04&(12(#(4&0.$#%(21$4&9(#'( $&-1$.&7(C+(A%2$&7(b# +&$(*0(G;T;K((b#+&$("#7('.84F(/#E0&.*Z&7(0&&7%&'(*0.1(-*&4&'( 12( 41$F( B*."( ."&( '18."( &07'( -1*0.*0E( 8-B#$79( '1( ."#.( ."&+( B&$&( #%%( /8.8#%%+( $&-&%%&79(C8.("(# $#4.&7(.1( ."&(01$."(&07( 12(#(C#$(/#E0&.(-%#4&7(#.(."&(4&0.&$K(( L"*'( 41/C*0#.*10( 12( -8'"( #07( -8%%( 4#8'&7( ."&( 2%1#.*0E( 0&&7%&'( .1( $&#$$#0E&( ."&/'&%6&'(*0.1($&E8%#$(-1%+E10'9(g8'. (%*F&(L"1/'10R'(61$.*4&'K(kX*EK(Gl(P*."(-(o(]9( #7%('.#.*4(#$$#0E&/&0.'(B&$&(-1''*C%&I(#(-&0.#E10(k]#l(#07(#('D8#$&(B*."(#(0&&7%&( #.(."&(4&0.&$(k]Clj(C8.(10%+(."&(-&0.#E10(B#'('.#C%&(#E#*0'.(&Q . &$0#%(-&$.8$C#.*10'K(( @.#.*4( $*0E'( 12( '*Q9( '&6&0( #07(/1$&( B&$&( -1''*C%&( B*."( #77*.*10#%( *0.&$*1$( 0&&7%&'9( B"*4"( ."&/'&%6&'( '& %&7( *0.1( '.#C%&( -# &$0'( #'( ."&*$( 08/C&$'( E$&B( \*K&K9( ."&( 4102*E8$#.*10(21$(]#(418%7(21$/(."&(41$&(12(-(o(GH9(B"&$&#'(]C(418%7(01._K(kb#+&$9((( -K(W]Gl(b#+&$("*/'&%2(."18E".(."&'&('*/-%&($8%&'(/*E".(-$16*7&(*0'*E". (*0.1(6#$*18'( /1%&48%#$(-$1-&$.*&'(\'84"( #'("//%#)%2*( #07(,+%0'),+0_9(C8.( *.(B#'(."&( 28.8$&(h1$7( i&%6*0( B"1( 2*$'.( /#7&( ."&( 4100&4.*10( C&.B&&0( ."&( '.#.*4( 4102*E8$#.*10'( 12( ."&( /#E0&.'(#07(."1'&(21$(61$.&Q(#.1/'(*0(#('.#.&(12(/&4"#0*4#%(&D8*%*C$*8/K T ( ( 7 Thomson, W. 1878. Floating Magnets. Nature 17: 13-14. 9 ( ( Figure 1. Static arrangements for n = 2 – 20 floating magnetic needles (all with their south poles oriented vertical), under the attractive influence of a central bar magnet. If multiple static configurations were possible for a given n, only those denoted by an "a" were stable against perturbations. [From Mayer, p. 248-9]( ( ( ( ( JK(JK(L"1/'10(#%'1(8'&7("*'(61$.&Q(/17&%(.1(&Q-%#*0(."&(4"&/*4#%(41/C*0#.*10( 12( &%&/&0.'9( C+( #''14*#.*0E( ."&( 08/C&$( 12( 2),0")*( 61$.*4&'( *0( #0( #.1/( B*."( *.'( 6#%&04+(\"(-$*/#$+(61$. &Q (418%7(g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kL"1/'10(G;;=#9(-K(GW<?WGl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b# Q B&%%R'(01.*10(12( #0(&."&$&#%(&,+2/"!'0'-#(!1))'-#_K(kL"1/'10(G;;=C9(-K(HW;?W>l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g&4.1$*&'( C+( #(/#E0&.*4( 2*&%7( '"1B&7( ."#.( ."&+( B&$&( 01.( %*F&(((( p?$#+'9( C8.( $#."&$( "*E"( 6&%14*.+9( 0&E#.*6&%+( 4"#$E&7( R41$-8'4%&'R( 12( /# &$K( kL"1/'109(G;>Tl( ( ( 2.2, A,corpuscular,theory ,of,ma tter( ( `A2.&$(%10E(410'*7&$#.*10(12(."&(&Q-&$*/&0.'(*.('&&/&7(.1(/&(."#.(."&$&(B#'( 01(&'4#-&(2$1/(."&(21%%1B*0E(4104%8'*10'I(\G_(L"#.(#.1/'(#$&(01. (*07*6*'*C%&9( 21$( 0&E#.*6&%+( &%&4.$*2*&7( -#$.*4%&'( 4#0( C&( .1$0( 2$1/( ."&/( C+( ."&( #4.*10( 12( &%&4.$*4#%( 21$4&'9( */-#4.( 12( $#-*7%+( /16*0E( #.1/'9( 8%.$#6*1%&.( %*E".( 1$( "&#.K((( 8 His first conceptions were in analogy with electrolysis. [Davis and Falconer, p. 77-8; see also p. 77-138 for details on the evolution in Thomson's thinking about gaseous discharge leading up to his discovery of the electron.] [...]... deflection ϕ1 due to a uniform sphere of positive charge would be directly proportional to N0 (the number of charges in a neutral atom), whereas ϕ2 and θ1 are both proportional to N 0 This implies – for atoms with a large value of N0 – that the dominant contribution to the total scattering would be from the positive sphere,... different atoms, from the inner rings (upper rows) to the outer rings (lower rows), where N represents the total number of charges in each atom The N = 3, 11, 24, 40 & 60 atoms would form a single vertical column in the Periodic Table, each member of the group derived from the previous member by the addition of a single ring [Adapted from Thomson 1904, p 257.] In a similar vein, atoms in the... charges from inner rings (top rows) to outer rings (bottom rows) for the group of atoms containing N = 59 – 67 charges Each has 20 charges in its outermost ring, placing them all in a single horizontal row of the Periodic Table [From Thomson 1904, p 258] With additional interior charges, successive atoms in this group would be less and less electropositive,21 eventually to. .. no choice but to concoct a hypothetical smear of positive atomic charge, which he likened (crudely) to "a liquid with a certain amount of cohesion, enough to keep it from flying to bits under its own repulsion."10 Thomson never believed in the literal truth of his mechanical analogies, and preferred to de-‐emphasize... single atomic encounter was directly proportional to the atomic weight A To do this, he defined a scattering coefficient K as the most probable deflection angle for a thickness of material with stopping power equivalent to one centimeter of air Geiger claimed that K should be proportional to the ... inside a fixed angle ϕ, which he then used to calculate the total number of charges per atom N0 according to both of Thomson’s proposals [Table V] Assuming the positive charge to be uniformly distributed in a sphere of atomic radius (Theory A) resulted in a nearly constant value for all the scattering... [Crowther, p.229-33] 25 “…the positive electricity in an atom is not in a state comparable to that of the electron, but … occupies such comparatively large volumes as to be capable of being considered as uniformly distributed over the whole atom.” [Crowther 1910, p 240] N 0 N 0 Atomic weight Atomic φ t m weight A B A B Carbon*... 1908a, p 156] 30 had to be an integral multiple of the fundamental unit, the evidence was strongly in favor of the former over the latter, in particular because a charge of 2e would correspond to the α-‐particle having an atomic weight of 3.84, very close to the atomic weight of helium at 3.96 “Taking into account probable... according to the atomic weight of the reflector [Geiger and Marsden, p 495-‐7; see Table VII] Figure 6 Setup used by Geiger and Marsden to study the reflection of α-particles from a metal surface The lead plate P is situated between the α-source AB (an active glass tube) and the detecting screen S (observed with microscope M) The only path from source to detector was by reflection... increases with the increasing atomic weight of the scatterer The anomalous data for lead was attributed to suspected impurities in the metal [From Geiger and Marsden, p 497] 1 Metal 2 Atomic weight, A 34 They next found that the number of scintillations they observed depended on the thickness of the reflector, in a way that was similar to reflection experiments . 1 Early Atomic Models – From Mechanical to Quantum (1904-1913) !"#$%&'()#*%+( ,&-#$./&0.(12(3"+'*4'( 50*6&$'*.+(12(!1%1$#71( )18%7&$9(!:(;<=<>?<=><9(5@A( ( Abstract( ( A(. continued to refer to negative atomic charges as “corpuscles” throughout the article, and for many years after. George Stoney claimed in 1894 to have coined