CIHM Microfiche Series (Monographs) ICMH Collection de microfiches (monographies) CaoMJian Instttuto for Historical MIcroraprodiictiora / InstHirt canadiMi da m^^ Technical and Bibliographic Notes / Notes techniques et bibliographiques The Institute has attempted to obtain the best original copy available for filming. Features of this copy which may be bibliographically unique, which may alter any of the images in the reproduction, or which may significantly change the usual method of filming are checked below. 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Original copiaa in printad papar covars ara fllmad beginning with ttta front covar and anding o;t tha laat paga with a printad or illustratad impraa* •ion, or tha bacii covar whan appropriata. All othar original copiaa ara filmad baginning on tha first paga with a printad or illustratad impraa* sion. and anding on tha last paga with a printad or illuatratad impression. Tha laat racordad frama on aach microfiche shall contain tha symbol >^^ (meaning "CON- TINUED"), or the symbol ▼ (meaning "END"), whichever applies. University of Toronto Gerstein Sciences Information Centre Les images suivantas ont it* raproduites avac la plus grand soin. compts tenu de la condition at da la nattet* da rexemplaira film*, et on conformit* avac lea conditiona du contrat de filmaga. 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The following diagrams illustrate the method: Lea cartea, planchea. tableaux, etc.. peuvent *tre film*s * des taux de r*duction diff*rents. Lorsque le document est trop grand pour *tre reproduit en un soul clich*. il est film* * partir da Tangle sup*rieur gauche, de gauche * droite. et de haut an bas, an prenant la nombra d'images n*cessaire. Lea diegrammes suivents illustrent la mOthoda. 1 2 3 1 2 3 4 S e 3 1 d /"?6-^r-/' A NEW FORM OF SPECTRO-COMPARATOR -tr "cr :nj " T KAi.rn i: 1)1 i.iKV \. ■ K.'l>riiilril i r pn. ilr . it. ill it i,im li..:n •r.n \M«ol•..V^. »onsfni»t a toniparatnr |>i)ss»ssinn n|M( i.il advantam's in thi- nuasurtiiuiits and (uiiiiiari^on^ nf |>liulii>;rai>li> of spectra. 'I'hc dtviir may l>i- arranmd in srvcr.il ways: I. Thi' miirosiopcs may 1h' stt up with thi'ir axes intiTstt tiiii; on either side of the oWjeitives and with the half >iivereil Mirl.ue at the intersection. II. The microscopes may he set up with the axes of thi- ol)jei - lives parallel. One beam of lijiht. after ])as>in^; through it-> objective, is turned by reflection throuj;h one or two ri;;ht anodes to meet, at the half-silvered surface, the direit or simii.irly reflected beam from the other objective. The half-silvered surface transmits and rellci ts in either ca^e about half of each beam; and tli imaijes, side hy side or over- lapping, may be observed in two directions at ri>;ht angles to one another. By emi)loyinK the arrangement I in such form as shown in the diagram, it i-- possible to produce, with a minimum of optit.il surfaces, two sets of images in con\enient positions for altern.itc measurement, the configurations appearing rotated i So degrees with respect to one another. In the case of sjiectra, one eNejiiece would show "violet right" and the other "violet left." Furthermore, in order to compare personal errors of measurement, two ol)Mr\ers could conveniently measure together, one at eat h eyepiece, viewing each other's settings or making alternate settings. (Sui h a nuthocj of comparison between two observers should pro\e vaiuabie in such obscrvaticms as the transits of stars, occultations, etc) To facilita' such comparisons in the measurements of spectra, the comparator should be made to rotate and should be set up on a narrow table with a seat on each side. To avoid the interference of reflections from the outside surfaces, the silvered surface shi)uld lie between two wedges or rectangular prisms of glass. 220 AM/./'// /;. nii i.i KV I'or ;irran>;rnunl li ihi' ll.irlmann ^jki tru-omiparator may l)r lasily adajjlnl liy nmuvinn the usual mImt ma>k ht'twtin the Kimpoiunts if the doublf-prism jjlarni IkIow the t'yq)ii'ci'. half- silvi-rinn thi- laic til one of iho i)risins, ami cTnientinK the i)risms toUitluT anaiii with Canada l:alsani. With this diviir the Harl- mann toniparator pussfSMs all the advantages it ordinarily has. and in addition the followinj;: I. One doul)le-i)rism sulVues for all eomparisons. In the llartniann .iistrunient various kinds of masks are made between r V- I. New Form of S|iti tro-romiiamlor II, Adapti'il Ilartmann SiMjclro- ii>m|xinitor K. i-yi'l.icfc; //.V. half silvered surfaii-, (I. nhji-itivcs; T. pholoKraphii |.l.itrs the romiionents of the double-prisms, to make possible the com- parison of si>ectra of 'esired configuration may be emi)loye\ir\K\n>K ai) ;inl,il>U' spiilir linrs may lie u^til when ih^ind. Thus «(ini|)arisi(ii> ami liiu' lii>f» linii^ jna\ In- niaili- al llu- -.iww tinif. J. When till- half silvirrd surl'an' i-- u-i |tu>-iMr In plan' thi' inuiKis in mimidtinc in onirr to iK'tci t ilitl\rtn>rs, 1,. 'I'hf tii-w (Icvici- makes piKsihlr thf fnii>li>ymf?it nl' the uuu j)arator lor nua>urin^' phntoj;ra|>hs ol >ptitra !>> Ihf |iromi-ini; iiH'tho*! su^jm'stril l)y I'AiTslifil, nanu'ly, lliat i>l ii->iiiu'. willi tin- ni-jjatiM- to Ik- nii'asviri'tl, a ]>o^ilivi- platr niaili- I'roin il. aiui placfd n-viTsi'd to iif^jativo ind loniul.' I l\a\f a(!apl4.| tin li irl niaim comparator for this i>urpoM- and lia\c fou i i' \ir\ sali^- factory. It ovi-rmmi's thi- disadvaiitajii- oi iln- nu ilif 'Acr^hrd has c'mj)loyi'd of slidiiii; p Im- i i-. I ■' 'u- sami plant'. Clhr dilVitiilty of having iiu- lllnis n i in i foriis has hi'i'H ]>ra( tic ally oviTttmic l>y lAfrshth>r of the luam-. ot !ii ■ positive and negative may !>»■ a'tered independ('iitl\ ihti- it possible, by malihinj; the ii\ttii>itits of the llo^ili\l and l or by increasing the contract, to measure the di^planmi- spe( tral lines of almost any charat ter. ism the broal !ine- in stellar s])ectra. 4. Hy o\erlapi)inj; the spectra no parts of them need !« out, as is the c,i>e in usinj; the arbitrary ma>ks of tlu' Harti-i m instrument. In Tabic I are jjiven the means of the mea>uremenls of dis- placements fpHKluced meihanically) of 15 lines i\X4ii)') ^oi) 42()i .0^0, intensities i 5), of six exposures of the spei trum of the solar limb by: (i) the ordinary methcKl of bi>,eitin^' with sjiider line, takinjj the dilTereiues between means of four settin^'> on tlu' middle strip and means of twu >cltin;,'s on eath of t\vo out>iile strips of spectrum, each way (violet rit;ht and \ iolet left)'; I." by measuriuf^ ne^iative (\iolet left) with positive of itself (\iolet right) on the adapted Ilartmann compar.itor. takitv.^ dilTeriiices ■ KoJjikitna! Oh<.endtory liullflin. No. ;:, km j. ' Juiirn.il Kii\\il A\lro>uimU'it Sodely of ('■JK.i;s»)n thi* mii>lacfnirnl in mm I'rohalilf rrror, >\nf,\i: line. I'rolialiU' frror i>f mean 'O o<>qo O OO.'C) o oooS Mran lisplaccment in mm I'rtihaMi- crmr, sintle line. I'robalilf I'rror i>f mi-an iMcani o ogo o 0^)860 o(>u4 o 00,(0 oo.'7 ooi7jo 001510 ooj() o ooJ() o 000.H o 0007 o 0007 o ooo4'o ooof< o 0007 II. IVlsiriVR-WITII .Nfci'.4TI\E. Igl7 I Mraiu t I i ; O 0(lQ.2 O 0700'0 07080 07040 Ohc;00 l3tH)!0 o(H^ o oojoo 00140 00150 00120 00150 00140 0015 o ooo5|C 0004.0 000(0 ooo.vo 00040 00040 0004 When the ailapled Hartniann lomparator is used, rcmeasure- nients of solar rotation plates show j;ood agreement with my earlier measures by the method of bisection of lines; and the comparisons promise to throw light on the systematic ditTerences in the measure- nunts «)f the same lines on the same plates by ililfercnl observers. For example, the measurements <>f ig lines, X 5506. o<)5 5688 4.56, Plate 1.845(1), iire: Bisirlion of lines hy spiJir thread: 1)l' Lury, mean of <) measures. loi i- igi6. is 1 618 km/si-c. I'lasketl, iiu'aii of j nifa>uri's. nji 1, is 1 605 km/sec. I'osithc "uithniHiilhc: KviTshid, I im-asup.'. 1016. is i 6,^6 km sec. Df l,ur>'. iiuaii of 5 measuas, igi;, is i 610 km sec. I'o test the a|>plicability of the new form of comparator to the determination of stellar radial velocities. I have measured plates of ^ (leminorum with positives of solar standard plates (or vice versa), .1 .VAir nRM OF .S /'/•;( TWO (()»//■ I M /OAT ii.^ I st'lt'ttinR plates whirh had hiiii pri'viously iiuaMirtd' itiy J. S I'laskftl) in testing the llartnutnn s|HTtr(>-n>mparat«)r. In>tiai. groups i)| ioiupariM>n liiu-i ami >{roups of stiilar ami •«i|.ir lims Ininf; aii>!ru- s«•tti!J^^ were made tin solar and stellar eoineidenies; and one on eai h of the two strips of comparison sjH'itrum at eaih rejjion. I'he plates were then reversetl and measured in the same way. I.ess than .t minute at i\uh region each way was the avera;' time expended The •asurements arc given in table If. and .ne degree of reliability of e measures may bo judged by the following measurements of a zero displaiement (22 regions) of solar standard 14(12 with positive plates A and H from it: 1462 with jKisitivc \, — o 0010 mm 1462 with positive B, —o 0007 mm; o 0000 mm; o ooiOmm;o 0004 nmi Mean, o 00006 mm; or o 04 km see. Probable error of single measure, *o 24 km sec; proljable errir • l" mean, *o 14 km sec. (It is to be expected that the errors can be lessened considerably by adopting Kvcrshed's methtnl of using negative violet left and positive violet right, or vice versa, even though the measurement is in this case confmed to u single comparison line ami a single sohir and stellar line a meth are close in the case of Plates 1527 positive .\ and 1520 negative, and much closer for 1527 negative and 1520 positive .\. For the former the probable error of a single measure is =*=o 4^ km ^ec; and for the mean. ±0.22 km sec; while for the latter the jirob- able error of a single measure is o 07 km sec; and for the mean. 0.5 km sec. This latter is a degree of accuracy seldom attained, 1 believe, for stellar plates of the low dispersion use, pp. iHj f. 224 RALPH E. l)F. LIRY ri-Kions. Accuracy of settinj,' is (IqR'ndfnt to ;i ^rfat doKrce on the cartful bahinciii),' of the intensities of positive and ne^jativc when making the settings or when printing out the positive. The agreement between the overlajjping-positive-wit h-negative measure- ments (De Lury) and the ah'gning-negative-with-negative meas- urements il'Iaskett) is only fair; and both measures seem greatly superior to the agreement of tl,i- solar standards or of the stellar plates. T.VBI.i; II .Mk.xsikkmknt.s ok f* (;k.\ii\iiki M iiv Two Mk.thods (I)f I.ury usiiiK i.<)>itivc with ncKalivo; I'laskftt usins the Hartniann molhml. ne(?alive-with-ncgative.) M C.KW. I'urt I Sin I'laik \o. OF I) (Dr. LiRv. .Measured knluiH \flmity Vclotily km, set", km, sec. 2 + C' l520 + .\ i5-'o-|-A 'S-'o+A 'S^o-I-A 1520 — 1520- 1520- 1520- '.S20 + A 15 20+ A 1520-l-A i52o-(-A 20 22 II 1 I II II 1 I 1 I I 1 II II 24.80 24.88 25.01 24 84 23 . 74 23 30 23 Q4 31.12 20. IS 27.12 2.i "0 20 31 20.13 26.09 26. 12 2.88 3.0S 3 ii 3 04 1. 84 1.40 2 04 1.88 85 '44 2 41 ' 05 I.OO 1 42 '38 1. 41 2,88 3" 24.7.S 24. 25 J SO — 0.02 1373- .2431 2 51 '373- . ■ ■! 47 -0 64 '373- '373- -5 01 ; 3. I I '373- . I 70 I 88 311 2 03 + 1.35 +O.IS '472-. ... '.i27 + A.. 3' .27 -'7 03 2 03 -'32 i5-'7+A . 1.S27+A... ■ ,S-'7+A... "44 1527- 1527- . . . . 1527- '5^7-.... '■45 ' 2 32 2.50 -f-o 87 2 .22 ' +0.34 The main advantages of the new form of comparator are: r. A minimum of ojjtical .surfaces are used. 2. Images may be brought into coincidence; and thus the Kvershed positive-with-negative method of measuring spectra may be emi)loye/• .sva /A-ocou/MA" lyo/v' ^. Twosi'ls of iniajifs an- ])rlr lum- pariitor. 4. In iniMsurinn s]>eitr;i. the instrunu-nt ni.iy hi' uxil in the ordinary way of hisi'itinf; ihi' lines with a spider thread; or it may he used as a comparator for overhippin^ t)r alijinin^;. for \vhiit\ masks for various eonli>;uration may l)e readily interi han;;ed SoLAK I'hvsk s Division Ddmimon {)iiskr\ xroRV. Ottauv April mi;