BSTJ 30: 4. October 1951: The Scientific Work of C. J. Davisson. (Darrow, Karl K.)

7.4 MB·English

‘The Scientific Wark of C. J. Davisson
By KARL DARROW

IE very first pie of au mich i plished by e physiciet who is
destined to be grat ie nat often aatstandig; but sorties i bas
cary finite aockbntavather thom ex, wl aspeets ofthe work
ne wus to come thereon. Ty es sae peper pulsed by C.J. Dane,
Tre End him working with elzteon, entrain has ino bear hy
the agency of mage Sal, dieing them aginst a moctal nga
leoing to sre -shether rye pote ftom he tage. Tr, the wees
Came from a soaetive subse, and therefore were rene fier than
ne of his later eaperiners. Twat so, he di aoe artoaly facas the
teres, True ale, the ays far which he was looking were Xray
find in hese he took o frie lnetest. Yet in meaty all a his sabseqnen,
runes he ae to uae some Ue principles of ele fosing ees:
Tron micrseyys im mang, he was ba ok fr hinge thst ware cited by
the tages on which his evieom fl Tas aiden pape was posed be
fave the American Paysiel Sie ab its meeting n Wsington 50 April
Tots a pistol seion may be Lavan toe Phil Raview, pgs 0)
eEvotime 28 of the year 1908, He te signed Com PEnceton Urey,
Sihisher Dia Fad gone 26 geo stad
Mroer dheracterte of Navcore wesk im his ater yes was i foe
qt study ant ule of thermonies. Azeady ix LOU ef han working
in thie ekl tat it wes thermore with a diference, The ord "ther
nics" mw sigue, nearly alwaya, the emision of electrons fom hat
frets; bot at fst tinh also the emisior of postive fous from ht
Tova and bot salts, Thongh ithe eles oe uintrcting, te ison
iC portions snow raed far Beso the fat 29 wich We me one
the mane of therm: cision of eect on ot metals one of
tie fundnmenta pherenna of Netre, ane ie wees ae iiiable, Tey
te plansiy conferred thee fy WIL the cifereace i he importace oF
{helt prennscun-emzeon of ws ons and emission uf ele on=—
tens for ess event than it noe, Davison, working water dhe Dis
Physiett O, W Richter who nas chen professor at Princeton, eta
Fate tt the positive Sons weit fom heated sls of ie alia metal
see oneedouaed tons of thee metale—that B to say, atoms licking &
“hg electron, He hk sowed that if gus fe preseat inthe tube, it ay
fevtance the number of the fons bat des not change thst character, Tis
‘aug senesauae won ow €. 4. mavseoN ma

work was presented before the Apil mecting of the American Physical
Soesty in 1911. Alatract the papers whic he there gave oly my be
found ia Pig Resins, ut Ce pubiatons ia fl sppaare? (és 1912) a
Piilsvphica! Magasine. Davison’ cole of a Baits journal was advised
dn ie rapa tach, at rus he eae it 112 Uke Phase
[Revi ed by no menns sscended tothe took etic holds coday. With
this wouk came to their end te contrbutions of his stadens yeas, end next,
‘Re ane im publaing ns 2a independooe invests tx
‘rom Davisco’s yours (1912 17) at tae Cranege Insitute of ‘ech

ology thee isa poper embodying etempt to ezieulte che optical dis
patisa of wolcel aycogen az of lium from Hobr's earest atom
el 1 ehow him presse of no een mth ernie, a

Tons the eate by ie wal mate ent an mlve & oe
ok quantum theory.
Ty Jue 19%, ce ht of Woeld Wau J, Dasisson came for what be

orgs oul Ie & tempest ob at ce iatietion then kagwe as tke
‘Resareh Laboratories of the American Telephone aad Telegripn Company
aul the Westen Fleeic Company, threster~fom 1925 a5 el Tele
[Ps Tarato, Now Go eer at a Yall was he able to devote his
‘al! 0 ork untraseed by the exgonees 2 wae. So far as publiston is
foncened, hi sesame pei Yous i 199, when he peeeeated to pa2ere
Telins the Anserisat Physsal Socity: on at the New Were maxtng i=
Fete one at ve Washo ting Ape Ta the fom of these
(svn ens! 0 tha KH. Geta, nue aso nt as
ie Uke peat dieovey uf cleteon waves in Ca ats it Finks wth that
see late. A Pidgeon

‘He two pus Eee sepreseted only by af abseacts: and this is he
sure sugested Uy onus te only contibatons polished cer
Thviston'sunuse to the devaing eieare ofthe orien alae bv
the fier, Be established east the remrkahy high electri ereon of
‘sisted meta ax contrasted with bare ails at due a2 bad
tear soho sugges, “he inyect of postive fons (omy the gas of
the tbe ayn the cays it Ire there emission. 1: the later,
he suuisd the rise abd eventual fll ofthe shemonie emission ws more
snd move aside is kid dow upon she meta! suace, end conte tht
the csi secure wlan 2 dette numberof ose moles i serembled
into a pach af dete size om the surface th muster of patches of jet,
the sght abe Sieve, ther declines as he deposition continues. According
tevlexgue of his, tes two papers fal shart by for of indicating te ex
tent of hie couteoutons to this fel aré one of them "atm tha Das
on Was excetvely serupnions abot patting hit woe i pl, bela
388 wr nr sesmew aueNNtee. yormsas, ooronce 19St

uviling to publish his oserstions uate fet sre shat he underteod
‘Nihal was caking pce, Thi au aii by another—she Ite Tl. D.
‘Aen nat to Fol! te bax. of Dirgctor of Kean in Bel Telephone
xboracres an its antecelen oginiccion—thal we Gnd a description of
evinin's Spnmerenininy hast” aow stanard ia the et, Ip Arvo
worl Le, Davison bas dened fon of sootcinate- pape in which The
Coordinates are power supplied to the lament absczee) aad thermionic
mission forincter, The coeadinate lines ace ao disper a rural
thot if rhe emision frm flnmen ses Richardson's relation, ant the
“ermal uation sata the Stefan Tllzmann ication, then points en
the char vlinting poner an ena or such © Wmer wlll an =
striptt Iine”

Thr paper presented st weting tard the ea £920 Gt was a joint
apes a: himel arc J. Weske) Doviewon gives Ue sheoey 9 t= emi
tion of ght fname, dees = deviate fran Lambert’ lw avd
Series ‘his hy rsuesiuent, A connection betwoon tis ard the sty of
thermionic maybe infer fom Une wards wich T coated earlier
Arnos cstription of Davisin's wowrsenision chat. kis work was
Dublin ful, sore tee yours ner in heel f the Opal Seity
2 seis

{We tora wow to Dain’ investgeions of thermionic emion fom

“These whos: menor go back 4 enogh wl eal hee so laws hve
‘ben sropmel for he dependence of theminsie sean on temperature
‘Both were pnpounded by 0, W. Kickanlan, aod ene somewhat on
ingly, host vines be eae “Rican le" The ene preva
thet the thermic emeen # 0ald vary ae Peap(_ 8/1), 7 standing for
the absolute tsrpecature; the Inter esis Cast ¢ shoe vary as
‘Pegpt iT). The former iederioe rh the assumption tbe the veloites
tnd enengs of he eletrors rsd The metal ate dit bed according 20
the class! Mexwelbntemann kw. The itor fll fos the a55-
tion thet thes welts al cuties ave dition] aosoling to the
thuatumetenry or Fen -Dirae ay a, lomeve, deed fom therm
Ulynanie armaments eae ehizton yous hrfore the Femi Tine theory was
Gdoveopee, snl theexperimests aboot be mato were petosmed daring
this tirteen ver period

Th the interest a hee hy, is coreatd wth the wor of eres
whi an elect nant do fa te epenee of Untie enxgy is ere to
to frm te nie bo cote of te mecl Tee alte ge he
Dhiastng ofthc eorelason, and sy for ‘he momeat chat 8 mpi hy
Tolremean’s naatent &rpsnsents hot wee nh eabed end is stil core
vu sauna wou o@ ©. wastes 10

tines ceed the “tesmine worksunetion of the mete. Ia give se a
das i ittod Est ly Lie Play ad an ly Cae T= a ier lacs of
‘ine therefore diferent vlses of the themsonie wotkfunetion are ob
tained Which right

Thi question an be anavered if the thenaonie work-unetion ca be
snes with diye acura yy some ther method, Sek = mes
ea eral the aliretee™ miko. Spare sn esc ie
surmmndes by a einésical eectode If she Inte is negative with eect
{othe formes, the em tes letras will ar tothe wie, ed een il
be no net thermal effect de Yo the ein, If owever the cylinder 3
postive with respect tothe wit, the eetron willbe dry tt ane the
rei al in temyerine Lsf he “emtg-et™ ea Ihe mi
Shon The ceitance of the wie wll deen, al the nee intr the
Wer le Hol constsnt, the voltage between is cenninle wl be Jessrad

“Te espeseat any eound eney, end so unig le ial of dhe cutent
sowed within tne wits om end to end bat the Heeding of Cectons thug
the entire surface es the czres vy frm pone to point along the ie,
‘and complicates the tat enormously. Otbeis elevle Iad tasked ie
‘licult problem of experimensstions bat Davin and Germer fad a
‘beter way to handle, ad thee raul fr tangsten were presented ota
‘aecting at the end of 1921 snd published fll che flowing year. From
"hei dts hey enlrlted the ehetmionc worksfinetion o che real, wich
rhe thus datarina we way deaate by ag. It ayread with cheval of
{vols from the nene form of “Richart lw lice wh the
oles. Thus Davisson was ia the postion of Lavin conned the Fea
Dane distribution law before it sd been stated!

‘Ie veriins tobe sid hat, yeas Inter, Lieviaoa and Gasser reposted
thiseapeient pons oside-coaed petro wire Mee Pry eae po
2 romplcaon from werk ran ret wifi ae formal eee

"Thecsnmicter the ide cote win chara with th terpenes ad,
sinoe the measureman® of the Yenaiant” Breguet the tem
favre, is value lwo peovide a raise ure ofthe work at any
Sng temperature, wera he “eaorimeci” mesure

‘Now at ast we are needy to atend ta the early stags ofthe stutie
whieh were destined ole ta che discovery of ekeeton-naves, These were
stalice of what T shall ell the “polgaystaine stieviag pater” of
retaa the seme i descriptive esther thay short, A beom of eleerons i
Srotrtedagninsen metal teget whith i in the condition, norm fr 2
Titi, of Eeing 9 complex of tiny crystals oriented in ll dretnne Some
1 thew elt sing cnn ol come ir tthe otal wil

vine nes Ieee The lean ice etic oe ee
90 re an semen seRTEAT JOUR, ocTORTE 1951

‘Davies: rcords shal eas storing had preioualy bo level iy
‘rth cevieos havi iitially an onergy of 12 eeeerrols ur iess).
Collector fate ae place wher iss uch electrons as ae eettenst
St dvectga waking sme chosen augle 9 wit the rection exety opp
sie a hae of he orgial or “pinary” bean. hens may De inelastically
Seattee or stcancany elias lic travel tovazd the colt: its
poten eu acjorted ax preven: he wens of che

he wale i movel Irom plans to pee eo 2 In osupy coco
portions weesponding to many vals ofthe ale @ Te aly i the
ue plese posing thong foe pinay brim, sas he curve of nes
tsattecedlectrons (er ni solid goal) pottal egaaet 0 is 2 cosa
Section of thee-dimesaioaleeattringpattra: But, for obvious e858
fof grrovery, the ineedimensiosal pattern ie just the tmeainensogal
Daler rtaisd around exe axis whic is provided the peixary bear
This tn ineional pattern [2 whet T have call the plycrystline
seastering pacer, Ze ies inept}, pal eonlaes in Cartes,
Signin # vee a mange of this angle which eatends Ero 90" co HNP;
ihe the part of che cure which runs from 9 = A" to 6= 0" The
miter image ofthe other er, nd ether by se sues. ‘The curve ~
Fi plotted inthe mmisie cnr af @ = 0, becuse the source of
the elactuoungets nthe ay

“Tae Ret publhal sept of sich sv experiment isto be fo, er
the nines of Dao 242 C, 11, Raza a Scaweraf Novambt 172
in thot sine November Devine presented te work hone che American
Physica Sooty. The metal wos ick, end the len had two mest
enable features, There were sharp abd prominent pss; one ineerel
To he Srend ofthe curve i Se eighborkood of # = O and presomaly
pointing i exactly that dino, consisting thereof clectrons shh
Fd bre Zvned clear acum Carwug 180 lees; the ater pining a 8
dlection wtieh depo on che epect ofthe Cectors, ard for 20D-clt
‘ketone woe a

“hay pbyellt who Bsas of experimencs on exces Ukely to think
cf the tottering eapecneate perormed by Rutherfonl now more thas
foxty years wish extasbed the nuclear etom model, These were
Inoaparements ofthe seatering-atter of alphas, nd this does mt
Took in th lat ke the eure niserved by Tayksnn and Kunemans it
‘lowe ro peaks a all Alpbnpetstes, however, ace seven. thousand ‘eres
te neire ws lectcnns they ave defected in the rune els, and so yest
isthe memencats of appari that it does nl sulle any pereobie
lef tom unless end anti iota wo close fo nucleus that there ae no
lectus at ll botyeen fhe noceoe worl But with ight partie
‘em severe oR 6, 2, mass ia

‘tas Geceon, and copay wth ay elect svg ax soy ay Davis
Sen's the denectioy commences when the Ang electron is stl nthe outer
feginns of the stou whic te penetrating. Le deletion of che lida
electcon ad che sealer pattor of the totality of the atoms are, Uhre
onc, condition not only by che nuclear field but by the Sel of =the
flecans suvoundiag the cleus. How aa. exe calculate Ue eft ll
the?

‘Tis is» very considerable memati problem, and Dass sop
ici tothe umest by converting the amie cectcas into spherical shells
‘of continous neantve enange centered a the rele, The simplest cae

Trivsblecge—not tn he stil th thao wckel—s that oft meas
rnd by a sng sheriealshl having ota! negative cara equal
“nrg ta the postive charge af the cles tae. Within the el
the el ic ie pure tcear el the stne as Laugh the sel wee not
‘here at sll ote ofthe shel. thee sro Feld all. Thief what Davie
ew cll! a lite il.” Calealaton shel tat the saterlng patter
febeichtagstem wont ve 2 pe inthe ietion @= O°, long the
peed ofthe eletrns id nt exceed cerain eigen there was
tore: "the main feature of the sattring paterae (Davison sid it
Teutio-cares") for ache inluding he ateral meu of variable pe
Ang area be expect te lel adn a ite eons aetange two
abel

‘iceland he represented, even tbe
rest dsrng allowable approstation, ae wacess surrey a eagle
“ets els is or escent bal Uv at tae bebe ony
Tl in the right dinstion ea sintcant one, Magresirm might reon-
‘ie sptonimated by singe hel del; Davison experimented this
etal, and published fin 1928) sattering-pates whi lent tenses
‘ell thie interpretatoa, Le measured enterng-ptterscf patina alo,
fel ese se expe mich rte wrk ith peaks wey
he ad of making rlelatins forthe piniry tom wth ty 7 elecrone

‘Wicket continued tobe Tavisson's favorite meal, and four years ler
(198) hs sty te pyerytallinescatteringatinn was il prog
rect To April of hal sear oouerd am acide, of whick I quote hit ow
isch en Physical Resi of Dacenber 103%."Dring the cova of
is srk a lidar bale exeded at te when ce lyst wae net
iu eupesatrg; the espesiuentl tobe wns lees ae angel avy
oxidized by the insuring a. The ovize was cveatusllyredueed abd a
Inver af thetargerrecoved by vaporization, but oni after prolonged hea
ing nt varios high temperatures in hydrogen nid inwacum, Whe ie
Fo2 mmm nian Sveti vecmpncaL JOURNAL, CETOBER 195K

experiments wee consiauedi¢ we Fouad thatthe diserbution in ae of
the sealed sects bad Bem oompletey charger. This marked
‘lteation i the seaterngp tem vas taced to ¢recrysaliation ofthe
“org thal cued during the ony heating, Before the uesdent sd
fn prevonsenparinenta we bod Seen bomberding army smal rytas, but
fn he tes aubaeguent the silent we were borabng only a fe
Taoge ns. he atual reser ef the odes =

Tilo it kim whether Dawson ever excd oc fai aig in xe Ln
pears a the rary; bt vel he might ave, “The explaing goidar
Tote Liew open the ate othe dteovery of electron waves, Fat onan
quences were not waning: the werent kill Uke urishing stil of
Doljeryallineseaitvng-patern, and enunlessSnteresting rare Jor
[any metalsar sll veiting ee coveres. This my state a der
nce between Ce instil sie scale carer. id Daw'ann Mec.
Stoeesor wit osce of gradi stents bessging sim for Vis sb
jects. the les of Physical Kaew might exh Lit deve of papers en the
eatterngpattcrss of many ile tetas, abtainot hy the scudents
se the master was forging aval i us: elds,

‘Nin that we ate on the verge a the achieweven whieh invested Dai
on with univenal ‘ane sad se corelate the Nobel Paze, Yan eit
Fistor in wore bie T note dom while al ry vequost he related the
story Uh sappeaet a the smerty ath of Janae, 1037 | ave these
Gf paper wh signed afer eng it ver a6 alse did pur cule
EA MecCall who was pest to hear the le This'sauthentl scary
Sch os al too oflea we lack for her eeoveras of comrsrale moment,
Listen ron or Davison itz resting, even though fv the thin! pein,
the won of the achievers.

The wtcrion of (| Daviaon wae ren un W. Elassers noe of
1925, which edit Unis wack of bec fe li ot believe tha
loa’ theory of hi Devin’) prion rnlte a valid, This wea
no inlucnce or the coun of ke experiments. What ezally tare he lise
overy nas the welldnwn acident withthe polsrytalie mas, wih
Sypeted tat single cnlals woud exit intersting ets. When the
Alcon wae mace to experiment with the supe crystal, was anciipated
that tranepuren’dietions’ of the Iitoe would be discovered, a 1976
Davison sad he gol Gorluse 29 vit Engl and eter the meeting o
the Brith Ausocition Zr the Adeaneenert of Siete Oxfon. He took
{sth hi some curves relating In the ingle cyatal and ey wete step
Jnaly Teese (surprising hor rarely desm ad been rere). Te seed
them tn Bor, ta Haccace ort pray to Blackett; Torn alain another
CContnealpbysiit (posi Franc) to ew them and Here was rch
At AOUSINNE WOES OF €. J. navision ws

Aiscusson of ther. On the whole of the westward transatlantic voyaye
Davison spent his time trying to understand Sehroedinges papers, che
then hed tn inkling (probly derived frum the Oxford dictions) thst
the explanation might reside ix them. In the actus of 1926, Davis:
fsleulated whee caso: the beans aught to 2, ake far the at il
tot Gud them. He thea nid aut» progean ef thorouph seach, aad
Javeary 1927 got teag beams de othe aegraags af te sla ates,
{ic showed By cleanin the sae moot."
‘Ne {ll sppement this icine i

to expats, The dest

same tbe mention inthe expats mast be one which does net

pee inthe quota hat of Lone de roi

Toni te Hof Paris get tha roo ie men
fume demi ify $n ei la wave o weet
ave op, stain fe Pans’ comatan. Tas geo be eden
inp tote nmi oa he ih erent
tuition antares eerton
ie Schetinger vo the diner of “vases” hat T tin
teas Sevodigs ane peat nthe qutatin. Highly eet
Fsthenfes ta hie Brg aves a they non can bee,
tig be dicta by tet of yt nd hatte estoy
Shes tes Sect ages esta gh all the ave na la
Sri dictoneaun can Kany
ty mire, then ser 1 Ging Tao nf the pea en of
‘none mong tats caper in Ele ar
Tiuhet latyuided Daron fo vetaton, vero wat wenn
Sy the ce txt sty lng to Esa or fr Bese “he it
{hee Dr Hananr ns tried nee pai hfe sai
Meteo Eni ht Hnten "Von ma, ye are ito
2 oldie” The eres Le mented opened in 85 che
iitutperidie’ Dv Tetursacnanton treet rien ey
tte aed hep weerngsatien nator tse
tec patium, the hat tore psedy Tieton Rosen at
Dike st we hae see id ntact ti explanation fhe pis
Sot necr s,s far ab Ela fate eve as anyone eel
Shin tal deine the pajenetlce saterngatere fen te nae
tho ecm Phic wa bested ne “ongtem Foe ne
Sete dogoten, Suber ef eet pve

nent. to the ap.eatn of Hae ion the fc hace wane
teagan ined th econ ef Convent Soe
{ine omer ef agua to exprence obese dtc fin 8
TM my nay somone mromseess yooRss, oeroaeK 1951

cuystal tee. 1 ety to stem dhl 150-valt electrons have wave
Tenth of ome Angstrom way ile the spacings Detreenavoms in sali
areal the oer of several lagatroms, This et of course did not ease
heses, ani figure in etter.

ran the ota i inca Lat the ent patterns obtains! fron the
oupaeo! Lage erate wate abect and the dafnicie roof 3 Fkts's
theory ve blaine only wien Daseon tiated is progen f thee
gh arch” and sultarcousy in Englad C. P. Thomson instituted
Iisown. Tre ater ites inthe quotation rege to br expla. Te
hypothesis w tanapacent dies ioe” I wil consider to be exlaued by
itsmame, Wee it ores, the rections of che ms woul be dependent
ff the speed ofthe eretron nace they are ety Hepes falls, Tae
ler tothe “ne grating ho surace ctor” inluces me fo peed
Wt oor Ue ene of the sna contmateheten dHDlaction of elects
td dgmetion o? Xm.

‘a opie gratia nojuence of parallel equiiten: grooves or rulings
ona suse of metal orglae, Treatnnmena cystlfnesifaceare arranged
{pw equidistant ins al ow might expet X-ray lezons tobe
Gifted fr Chen e8visleTighs i ilfested from an aptial gesting
“iss expectation i reteset nthe ease of emp, hus er power of
neat & an grea at single layer of ators, bei he urfacelayer
fe ary miler, dicts ber <1 faecinb © part nf the incident Xor
Seam: enly che cammlnive slat af temy ayer leletable. Elector
si ahim ae dose thit Davin usd are ot reary 0 penctating, With

Theat indeed it peble, ase wes the fst
trans prviurnl by Ge sutaceayer only Such beams, however, aredccte
ble oly wien the iciden forthe eerie) beer of eectons almost
ence the tstaes ab) wency aye, wher 8 beam ie observed, it's dae
fo the cumvlaive elect of mary atomlayes as the rie with Neuve.
Suche ceri oot votes mone spel conditios an does dit>«
tinny the sniae leer tthe incident beats let » given age epon
the snue, he wonentum uf the elctons and the wavelengt of chest
troves mint Te just nti jan it, aod revere ifthe momen
Thm ti letrons hae give value the ange ineience must bra
[sed une jot right. hs so Daveson veri

“As soon 5 Davison als kor bis demonatracion of wetron waves,
nena hemhane’ iy exces for sees Ais work sd fe desaipe
ons to be ywhivicl ix pools hey acvaneed snd specabzed Ga
Phricel Neves Tas saber af tex he eldad, and rscrmead espee
ely the tale whch i the autumn of 1929 he gave before che Mie elo
‘Meeting of the Optio Seiely af Americ; fda it a print in wolerse
"ay SOUNTIE WORK OF C.J. DAMON ws

18 ofthe Jouzal o ct Society Tis witra wih such eet, gree ae
Trror ae tu make me reget that Davison yas aot ofenertezped to
ceaploy hic talents for Uve beset wot of lynn precise, bat of sceatists
‘pho were laymen i respect to the Held of is rears grote che fist

rs atteace: “Wea Telacoveed on long ov the sanrecneat of
he mosting ae Araue Corapeoa isto speck om X rus ae a Bras of
COptice Trelined thet | lft rmule the mast opportuni. T
sould bave made a enila apgee to the ateton of he Soiety by chaos
Inga my abject ‘Lsetoas a a Branch of Ones

"Though in this peti hie duties espitor sok aga dal af is ine,
Davis found epparteniy to procete his wor ata egin wi certain
spplcaiaas.Oue ebvious development many be dsmised euler ear, =
Detng lee iteportnt than sight sonal sen Out mit have ex
pected Daven tm sre to cory de Bross aw — 8p 0 ve ar is
eilcan figures, "This would Lave been dleul if not inpossibe ince
‘hese tn ein of eectears ae uc ee tarp thin howe of X-mas
thin raseqenee ofthe fact tha th neion i ertormed by ony
fer Ivers of stom, te prinuey am being absoried befor ie can pene
Conte tpl int the crystal stiuture. Bue even fit nd been ey the
cnterocise woul probaly have bes couse fut, for de Boogie’ Ie
tick ehieved the sats being vegan a el-evidoney tn, Sch
the iis nvalves inte theories ao many nna, Hat if wore
fn erer hy only seal! fraction a «por ces, the discepancy mon hve
been tte Inyo fn mae ways than ene. Davison eatalished the aor
whit ore perce wil Htc ave fw wi wel aoe gerd shee amply
tishactry

ine grist of Ce uses of egeton-iffactin Tes the aed of the
arranger of na in exystes ana in nen-ersetalire bode Here
tenes the sir nee of Xora ea or, eserves where Xray
‘ifgetion does noe nd rie sree. Ono mre T wate Tra a loot af
Daviston's "lectrons are n0 more suitable for examining shects of mca
by tension ‘han rots aneoutabe fr tplecing seein window,
‘To be eine for ee nioaion “yy eectcns by tana, o socimen
must be mo more Li a few hundesé angstroms in tiveness, Tt must be
jst the sort of speainen which cannot be examined by Xcays, Massive
Specimens rai enaccned By eetons by selection, ‘Tae boom erected
tte te siace at ucasmzing “tSencs ond she hahye-tery wt
Preiel reveals the eretaline state of sirber-layer nf come Une
fist, Tanisible lus of material diferent chemi from the bulk. of
the specinen, ame Srngeelly disweved by his method.” Many exper