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New Tofk '4609 'J5A ■■=S •16) 48^ - O.TO0 - PMofi* ^= --ft] 2afl - ';989 - F:l" DEPARTMENT OF THE INTERIOR. CANADA Hon. W. J. ROCHE, Minister; W. W. CORY. Deputy Minister TOPOGRAPHICAL SURVEYS BRANCH E. DEVILLE, LL.D.. Surveyor General DESCRIPTION, ADJUSTMENTS AND METHODS OF USE OF THE SIX-INCH MICROMETER BLOCK SURVEY REITERATING TRANSIT THEODOLITE 1912 PATTERN By W. H. HERBERT, B.Sc. BULLETIN 34 OTTAWA GOVERNMENT PRINTING BUREAU 1916 TA S90 C3 l« h.34 e.S Canada. Tapaaraflwcal SiirvayB Branc Dafcriftiaa, aSjwiinviit and maMiads 3 liSQ3 IS'^aaOMS c i f f CONTENTS. GENERAL REMARKS PAL. 7 f DESCRIPTION AND ADJUSTMENTS 15 MKROMKTKR MK ROSCOPKS 1. Disc ript ion nl MiMi>iK'» 15 K><'-I)ii'< r . , IS Ki'iiiov.il i>( Ivyi-puTf. 15 MiiniM ii|K' I'.trri.iKi' .Ti'l I'i.iphragni , 15 Mirn)^r()|H' Conih 17 Mi( nunriir N riw .iiiil Drum 17 Avoidaiuf of l.o^t Motion 17 McthtMl of Ri'adinK Miirostopc 19 Mii'roscoin- Olijcitivf 24 Mirro'<"opf Ri'tUctor 24 Microwopc MaKnifi<'ation 24 illiiniinatint; thr I.iinb. 24 I rinciplf of Mii ro^(>(H' Acljii'tmi-iit 24 Cinidition ni Adjii^tnunt 25 IClimination of Parallax 25 Adjii-tini; the Run 25 I'urthiT I'recauiions 26 Final ( orrii t ion of One Mii romcttr M icrosco))*' 26 To Olilain llir .\Kan Value of All Runs 20 Kxaniplf 27 Final Adjusinirnt of Position 28 Distance Mi'lwi'cn Mirrosio[K's 28 Final Tests 28 tki.f.s(()Pf: i;vi.-pik( k mu romi.ikr 28 Description of Telescoix; Kye-pieee Micrometer 28 To Remove Complete Micrometer from Telescope 30 Telescope Diaphragm 30 ReplacinR the Spider Threads. . 30 Dia|>hraKni Illumination 31 Makinj; the Threads Horizontal and \ertical 31 Cenlerin^; ihe Diafihraum 31 Collimation 32 To Ailjnsi the Micrometer Drum iZ Method of Reading Micrometer 32 Telescope Focussing Scale 32 Stellar Focus 32 Micronuter \',duc AtTected liy Focus i3 Determination of Micrometer \alue and Kiiuatorial Intv . cals 33 SPKITAI. LKXFLS 34 Latitude f.evel 34 Stride l.e\el, 34 Deleniiination of Level X'alue 34 SVSTKM (>F ILLLMINATION 34 Distribution of Lamps 34 Battery 35 X'olt-Ammi'ler 35 Rheostat 35 92,?05— 1 1 2 3 METHODS OF ISK. Kl WIM. I III I IM. I Mill Milk: iIk I.JiH lilriiiririi Ml .i-iiri nil Ml ul Di-i.iiii' ollslKMNt. \/l\ll III "Mitiii^ ii|i thi lii^lriiim MI (HiMTMin; \/tiiiiiilli on iluri/iiiii.il ( in Ir ■^IH'i initn ( Mt^i r\.(iinn> (Mi»rr\inn A/iimilh with l\\r-pirir Miipiniilrr ^im inirii < )li«i r^,ltilln■■ l irnrMJ Ul ni.irk- (in nliMTx inn A/iiimlh uiim;i<\ in*. I, Aim 1)1. NlliiiK up llii In-lnin rill OliMTN illK Lalilllilr S|Hi iini n I )li-rr\,itiiin h.il.imriil \\< 1^(1111! Mil rciiiii Irr I )i'lrrriii 1 - |)i h rinin.iriiin ul Mii rmiHtiT ( urnrii' ■ I'rulMl.l.' Krr.ir I iriii r.il Kriii.irk^ oil nli«ir\ in< l.aliiiiilr ()ll--l K\IN(. IIMI AM) I.()N(,I II |)i; INDI.X OF M MUKKI.I) I'AKls PAl.K .17 «7 W M W m 411 ,W 48 46 47 47 56 5S «>() til 62 h.\ 4 ILLUSTRATIONS. rAc.i. Klyiiirr 1 ln»lriimin; Sci I'p f,)r Riinninn Lines. .8 I. In»lnimtnt >i't I p for ()i)r.irviii^; Tiini' ii'id l,<>t>Ki"i'l'' ■ ' " .'. Instriimiiii "^i I I p ('>r Olm-rviiiK .'.zimiith nn the llorizoni.il CinK- 10 4. Iiwiriiimni S< t I p (ii * irvint- Azimuth «ilh llic Kye-piiri' Micnmuur.. 11 5. Iii:.iriinniu Ni 1 p fur ( >ll-^r\ill^ l.atituilr, I.cMikinK Sdiith. \ ii'wi'dfrom Ka^t. \2 (i |n>lriinunt S-l Ip fur OliMTvinn LatitiKJi, l.iMikini; North. \'ii .1 from Ka>t. 1.1 " 7. Instnimi'iit Aiii'^sorii's . . . !■* S. Side \irw ami I'art S'rficiii of MiB. Nomogram for ("orrectinK Micrometer Value for Krro! of Run 22 " 10. Front \'icw of Eye-piece Micrometer with I'over Removed 29 II. Siile \ie» and I'art Section of Kyt'-piece Micrometer ?9 " 12. Longitudinal Sections .ind Switch I'o-itions ot Rhec aat 36 ^ GENERAL REMARKS The transit theodolite used on the siinev of Block Outlines is described briefly in Appendix "D" of the Manual of Surveys. A Block Surveyor nia> . in the course of his work, have to perform the h)ll()\\ing operations: 1. To run a straight line. 2. T(j turn off or measure small angles, such as: The deflection of base lines at township corners, the measurement of the angle between the I ole Star and the meridian, and the telemctric measurement of distances. .?. To turn off or measure large azimuth angles, such ,is: The turning r)tt ol base lines from meridians, and the measurement of angles in inangulalioii--. 4. To determine the direction of the astronomical meridian. 5. To determine the latitude. (). To determine the local tinte or the longitude. Accuracy in running straight lines is secured by a long transverse axis, a powertui telescope, and an eye-piece micrometer for measuring small deviations Ihe ineasurement of small angles, either horizontal or vertical, is made with precision with the I'ye-jiiece micrometer. Accuracy in measuring or laying off larger angles is obtained by micrometer microscopes. The powerful telescope, eye-piece micrometer, diaphragm anil sensitive levels render the instrument esijecialh- comenient and accurate for the determination of the meritlian by 1 ole Star ooserv.it ions m day time, of the local timebv meridian transits and of the latitude b\- lalcott's method. Ill u-ed without the dam]) of the transverse axis for running lines, fig. 1- lor observing ' r local time by meri.lian transits, fig. 2; and for observing a/imuth 111 d.u time, iigs. .^ and 4. The clamp arm is put on for making instrumental adjusiinenis and tor latitude observatioii>. in whicii case the instrument is used as a zenith telescope, figs. 5 and 6. riuse instructions and explanations h.ive been prepared f(jr the purpose of supplying to surveyors only certain re(iuisite informatiim not readilv obtainable tnmi text-books, ami also certain informal ion peculiar to this tvpe of instrument. I'KilKE I. Inslruiiiint Srt 1 p fm- HuiiniiiK I.ii KiiM HE 2. In.-truniiiil Set l|i for OhwrvinK Time ami I-on»filudo. , . , , ^ , !■,. t..r (>i.w..., I.,.' V7iiiiMt!i iin till- lluiizDiitul Circle. 10 ■ u ,, ^ ■ . A k.r ??^^PW^gff Figure 4. Instrument Set Up for I )l,«.rvms; Aji.tmth with tlf Ey.-pi™- Micrometer. 11 ,: .'. :'.}» S%tS!n K tt C V W ' |.„aHr. 5. In.liu.iMnt ,S.t i;„ („r Ul.>.. w">i I...tiiu,lr- l.o.,kin« S.mth-Vu«c.l trnm Eu.-t. 12 mmmmmmmmmmmm mmi^m^mmmm Tua KK li. In^iriii.icnt Sn Ip (or ( )h>-<'ivint: Kiitituil. l.onki.!.' Ncrtli - Vi.ivcd from KaM. ,, 13 I'li.i lii. 7. Iii-liunic lit Ai-ii— I'lir.. 2.V 24 25. 2() 27 2S 2'» M) 31. .?2 M ,?5 L.tnip llol.Kr .iiid l..iiiil> l"r KLulinL; \ triii al (inU-. Klir..-i.n ,inil I. .111111 l.iac!-. U.iturv l.i.iil-. I.,iri;r Sircw |)ri\ir. >m.ill Screw I )ri\>T. Wri-mli f,ir I'ripo.l Nui-. Kc> fiir Shilling IriiMiii llciil. riumi.-i...i.. Siriilf S.ility IlolcKr. Tilc-i "1"' Mirror .mil C",i-r. Lamp llutdor-. .iml l..mip> i«r lllumi- iiatiiii; |)iaphraL;iii. Siriili- l.cM-l. taiiul Hair Hrii-h. I.aiiili llwl.Kr anil Rctlcctin.; Mirmr a-.il in ( (li^i r\ inn laliiiiiK'. I.nni; Dianiinal I'.yt- I'irn-. Ilii;li l'ii««r Invcrtini; I^Ni-l'irn- ami I .i\ir-. ?7 IVi-nialir l".\i-l'ii'Cf anil Cnvir ,>s l.iiw I'nwrr liui-rtinL; Kyc-rii-ri' ,?') Mil, ill X'lriiial ( in U- l.iwl. til l.arijc .\iliu>linn I'iii. -n Sraatl .\iljii>linij I'in. 42 l.iKlit Sim ('ita>s. 4.? Dark Sim ^ .la>>. 44 rran>\ir>r .\\i^ (lamp. 4,^ l.aiiuiiU- lavcl. 4(1 Sparc l,anip>. 47 I.aliliiilc Slop (l.iiiip. 4S Bottle lailiricanl. 4'» li.iulr W.u.h Oil. ,>0 --pare Latitude or Mriile \ial. ,M sp.ire \ertieal ( ir, le \ ial. 5_> ^pare I'late \ ial l.ari;e. 5,< Spare riale \ial small. 54 In>triitiient lover. 5.^ ielex'ope I'lll';. 5(1 ^\ln l-'liade u mmmmmmmmmmmmmmmm DESCRIPTION AND ADJUSTMENTS MICROMETER MICROSCOPES tnuu.l i^ a .ik.U> -t ,nn,,«,unr..i.f (-mM^inn ' .„s U n,u- of wl,i. 1,. (.2. i> ,lu. uhjer, l.n.. .lu- otluT Iw... . an.l (.. 1urnu„« riu' ami>lif>ii'K l<"> i> nmiit.-.l as x\u- luul .s imi miuircl in l)f fxuiiMvc an.l itu' iiuaMirc i- nia.K- mMr il. .iiitrr. \\\n-u firmlv f.M.l an.l irulv a.liuMc.l, u is .apal.U; .;f sul..livi.linv: tin. ,ni,u„Vs n... s..;.n.ls ^^i,h ^r.M a.rura.y ami .as.. It a.lnn.s .. tlu- d.v.s -n s r,lu. li,„l, iKiuK well ilh.nnna,...!, an.l .l.-.s n... ujjur.. dun, hy fruiuu, as f ;;:;, ^s'whh ;i;;N:;;u.r::v;:r;;.n.;h ,, ......sses a.. ,1. advanu... ........ v.niU-. (•..n,l.in..l xNitl. l.i^;l. n.av;n.t>inK p.-w.r an.l n..rr..n..ln. al n...t> .. nicasuR ....nt . hsvah... h.Avev.r, is.niinlv .l.p.n.lfni ..n iis hcinu kept in ,Hrf..;l %y..rkinji ,.r.U.r a,ul t,u. a.lius.n.on. ; tor wl.id, r.as.m a kn..wU..l,.. .-t th. pnnnpU.s .,t its o..isln..-li..n is .-s.nlial I., an ..l.scnvr \vl,.. aspires H. ^r.al pr..-.si..n. FVK I'lKCK. Tlu' cv.-pi"-^- '""^'^'^ '>f '''^' 'Iraw-ml). 4. f.i;. S, in xvlii.h ■vr. .n.mnf.1 .a.h in iis .,wn .-.11. ih. i\M l.ns 5 an.l tl,. .ye l..,s (>. .Ihis ;\.T. ' - .sM.s an ...mivaU.u In.al Wu^iU ..f al...u. tl.r.O;.,uaru.rs .,1 an .n.h an.l is i.K '.ss.,l .... X\u- ^lass .liapi.ra^n. 7 by U.rni.,, llu- sw.volL.l f...i.ss..,K nnl T.. ..l.Uii., .listin.l visi..,. ..f ll. lin.s. plac. a slip ..f white; pap.r u,..Kt ill. microsn.p.. Tl.. lin.s will tin., 1.. pn.i..ud up..n a l.lank li.l.l, ... wh..l. siai. Z 'v. s l,.U.r ahl. ,.. ju.l,. ..1- tlH.r .liMin.;.n.ss. N.,w mm th. fon.ss.n, - ' ' .l.tin..l. 11..S IS a p.rM.nal rinir 8, f.it. 8. ...nil ili. lin.s ajip.ar sharply .n.nl an.l ^ ari.s with th. I...al l.iiKil. ..f th. .>v .>t ih. ..I.s.rv.r. a.liiisi- il.i;r.is, i.i.los.d i.i ih. .<.\.r 10, tix.d ..v.r th. .y.-pi... f<.r .n. ''. d.tl..tinK al)..ui and h.ld in pla.i' 1)\ two small s.r.ws 11. is v.ni.n.. in r.adini;. Th. prism c.v.r lt>. is j.aini an.l .nusi.l.: insi.l.. for th. pt.rp..s. .,1 al.s..rl„ns: any .vtran...us ..Hsi.l.. for th. purp..s. ..f >upp'yin,^' a l.lank h.l.l up..i, uln.h th. ' .ircli' it;ra.hiati...is may 1.. vi.w.d with ^r.at )...xh insi. lii;l.t ra\s ma^nit'.d iniaij. <>l ih di>liiu-tn.-s. ht.nzi.nial R.inc.\al (ll th. .>. .,1. l.\ t; kiiii; mit th. )i... ii.a\ 1>. .It..l.;i slid.sin Ih. sl..l 1.^. an.l tmnin^ th. swiv.lL.l t...t..smi; .ml 8 K. th. .ft n, .1 ,l;;:c.x-.-pi..-. l..o..tt.s .li^...uaK..l. S..-on.l, hy m.s.r.w.n,' ih. .y.-,,....^lr..nj th. top .;t th. .ni.n.m.i.r l...x 14. Thinl, l.y r.m..v.n^' th. L.nr s.r.%v (u.. ..uiM.l. MT.ws If., a.ul liftini; ..It ih. t..p ..t th.' mun.m.t.r ...x m.tlT.d is th. <.n. l.v which acc.ss i-~ Kaincl to th. micn.m.l.r box l.s and th. Thi'- third riu i,il>lir,it;.ii b\ .11..H.S MICROSCOPK (ARRI.V.K AND 1)1AI'HRA(.M cirriaii. 17 rav.ls back ..r forth wh.n th. micn...i.l.r s.;r.\y .s ."otaj.. . .,f ,h. mili.d h...d. This .arria^H- supp..rts th. ^lass , ...phra^.n , npo.. wh.ch two pairs (.1 lin.H ar.' i-nL;iav,d .it r.^ht an^l.- to each otlicr, Th. pair of lin.s 18, tit;. 8. which aj.p.'.irs at riiiht angles t<. ilu 15 . . also tiu. '>. horizontal cird. *'T(.-*P'.1 1 „., ,>K s. >ulv Vi,.» M.,.l l>:.r. S,.,..,.„, nf M ,..r..in.t,T M l.Tn,,o|».. 16 ^r.i(lii,ii iiitis. -iil>unil> .111 .ipiMrciii ,iiii.;lt' nf .ilmui fniir Tuiiuiii— on tlic (I Ic \\ lull \ii\M(l llirc)ii^;li llif r\ c-iiii'ci', and llic piirl of tlii' jjr.ulii.niuiis iiuiti,. .1 Ik iwicii iliC'C iwii line- i- ilu' p.irl ii|n)i\ \\lii«li ,ill rc.i(!iiin«. ■ire to lie ni.idf. I'lif pair 1)1' liiU'K \') whii li .ip|MMrs ])aralltl in llic liori/niii.il (ililfii an appan-nl .iiiuli- nf alioiil diic niii'.iilc on llic circli' wlii-n \ii\vi'(l ilii>u^;li the i'\(-pi( rr, .mil thf iii^iiic lir-ianci' x'paraiiin; lliix' two lino i> ju^i .1 lit ill' uri'iUT than tlii' width of a uradiialion. The ad\ai)t.i^;i' in ii>inn two lint's l)la(('d closi' toj;i'iht'r omt u>iii^; a single liiii' or .i point is tli.il tin jiair ol liiii's aMTajii's an\ small irrt'j;nl.iritii's cxistiiiK in the yradtiatioiis, thus nixing n'orc t oii»i-lt'iil n-adini;-. M !('!<( )S('()1'K ( <)Mii. In pi. ice of ilu' ii-u.il coinl) ixisscssinK man\ ttrlli. lluri' is list (I a 1)1. ink coiiih or indi'\ pl.uc JO haxin^; lint a sinnic iiol< h upon itst'd^t', which liv'>\t'ry closr to the ul.iss di.iphr.inni, its .iiip.iriiit dis anci' Iroin the ncartr line lifinj; aliout a niiiuiu- of an' on the circk'. I'lu'ioinii is a strip ol l)r.iss doM't.iili'd into tlii' i'omt ol tiu- niicronu'tiT hox, and ri'inains -l.ilion.ir\ while llu- diaphr.i^;iii mo\t's. It is attaclu-il to thr left iiid of tlu' niicroinc'lrr hox liy nu'.ins ol ihc iniddli' strew If) which projects thron^;h the ^ni.ill sieel spring .^7. thus siippK ing a means of mo\ in^; tlu- notch in the lomi) lo ,iii\ desired iM)sili()n in the tield of view. MKKOMKIKK S( KKW AM) DklM. The micromeier screw 5K i, ri^idK atlaclu'd lo the milled he. id .s'>. while tlu' micromeh r drum ()() rotates on the sanu' ,ixis. l)ui its position rel.itiM'K to ilie milled lu'.id m.i\ hi' re.idily cliailKi'd. This is a<'com|)lislied 1)\ loosenin); the small screw in the centre of the milled he.id .s<), and holding lither the head or the drum while the other is rotated, ''"he micrometer screw has forlv-l'ni' thre.ids to the inch, one re\<)lit- Iion corresponding' to (i\e miiuius of arc on the horizontal circle. A positixe, const, int com, Id between the threads of the inicromi'ter screw and the threads ol the dia|)hraKm carriage is maintained 1)\- means of ihe two small sj) '.igs 61; hut all setlin^;sof the micrometer must lie made li\ screwing ui); i.e.. 1)> ri'tatinu the micrometer head in a clockwise direction, for the i)ur|)<)se of axoidiiij; any lost motion due to friction. The micrometer drum 60 i> di^•ided into five eiiual parts, each iiart rejire- sentiiiK otU' mitiute: and these minute parts ari' each subdivided into twelve e(|ual parts, each p.irt rei)resenting I'ne seconds. The lifleen-, thirty-, and lort> -t'lM'-si'cond marks are longer than the others. Single seconds may be re.uliK estimated b\ e>e, but it must not be i.cferred ihi't the precision of the instrument is an\ thinii like this. AVOIDANCK OF LOST MOTION. It has been mentioned that the seciiiij; on a dixision should always be niadt' 1)\ screwiiiK tip against the sjirin^s. This i? done iti order that thi' shoulder of the micrometer head may be made to jiress steadiK on its ])r(iper bearing. When the milled head is released it lea\es its bearing, and iV screw is not retracied but for the action of the springs, upon the efticienc>- of which the iiniformit>- ol the motion of the mi romeler during the releasing jirocess entirely "le|)en- and steadiness of action is maintained in immediate obedience to the rotation of the micrometer iiead. 92,^05—2 17 ^.i 4 lUuMiii^ Er:| A. V i iv IMACi; eORKlU I Sl/Ai CIRC1.I-: ; 20' KI'ADINC, : 21 .\'>M U -2 .!M n. F = r5i lMA(;i; loo SMAI.l. H-2'it/ REAl)lN'r. = i77 .^o'tT. vtV ^;^^,„ jl_^,^^^. =. 177° jl' 57:5 EL i I'- .< .«8 iMAr.i-: loo i.ak(;h ClKCI.i; -,«2(r" 10' RI-.ADIN'G ,'2(.' 10 +,!' .18'> 5+3 .(8-3 28 ' B 3 2A =,126 13 31.0 Fl ^ Er liaiiiE !). Mcth.iil -it KcaciiiiK M AcliiiK Micromctrr Microsi'opo. 18 :; MKTUODOF RKADINti MI(R()S( DI'K. -Tho nuth(Kl<, roadiiiR atiKlis Ity till' list' of the ini(Tost:(i|ifs in illuslr.iiid in fiK. 'J. A riiulinK is made li\ sinMriniiMisiiiK thi' jyair of l>is(r(ion lihts upon thf Kr^diiaiion l> inn u|h>ii f.icii sjilf III ilu- nuicli in ilic indi-x plalr mi that ho gr.uliiation jiisi tills the spiicf lictw-tMii the two lin"s. In all c-as.s it i:* imii- iry to road and record the values obiaiiii d !>> silling on lM,th the forward and liaekwar I divisions; that is, on thi' divisions to the api>.irent left and righl of the notch, resi)t'ctivel> . When the forward and liackward readings are e(iiial, the total reading is olit.iiiuil diredU hv adding the drum readins to the circle readiiiR as shown at "A." MowiAer, this equalit)' of the readings is the very rare exception. OwinK to errors in the circle Kraduations, to the fact that the distance hetwi'en the mii rosco|H's and the liinl) varies with the tem]K'ratiire, at. .o slight errors in adjustment whic h are iKiund to occur when handling; the instru- ment in the lield; it is almost invariably the case that the ima^e is either too larne or to') small. The latter case is represented l)y " H," fig. 9; while tee foriuir is shown 1>\ "('." Tlie inethiwl used in deducing the final re.iding is as follows: I.ei F- forward, or apparent left, reading. Let n = backward, or apparent right, reatiing. Then distance between readings is eciual to 5' + F — R. F-rror of run = F — B. Correction to F= — F x F-B 5' + F-B or, corrected reading = F — F .\ F-B S' + F-B = Fx 5' 5' + F-B ■ This applies both when the image is too large and when too small. This form is not very convenient for practical use where a large number of reductions is to be made. By multi[)lying lK)th numerator and denominator by 5' — (F — B) the e.\])ression for the corrected reading becomes F 5' (5' -F + B ) " (5')=-lF-B)'- Now as (5')» when exjiressed in seconds is 90,000, nd (F-B)' is very seldom as large as 100, this latter term may be dropjied with .introducing any very appre- ciable error, and the expression becomes .S'-F-t-B Fx 5' r 1 F-B or F — r-, X (difference). Where the error of run is considerable, the absolute method of reduction '•hould be useil; but wherever the error introduced by using the approximate form is negligible it is much to be oreferred on account of its simplicity of appli- cation. The differences l>etwev the results obtained by using these two methods for all errors of run as high as ten seconds and under the most uiifa\'our- able conditions; i.e.. when F-.S', .ire given ir, t"- ■ following tabic. Where F is less than 5' the difference will be less in the s....ie proportion. 92305—215 19 r" I'ii;i iiK !iA. Al>:iiu- lor I .prriii mn Miir.imrlcr Wthn- (..r Krrnr of |{nn. 20 i Fiiii Hi: ItA. Ali:(nir nt' Hun. 21 CORRECTED 1 MEAN READING S. f. ^ ?', ^ '. I i. I ?: t ; MM |) M i|' 'M l | l h ! ; ! ' M| li " ,ii,ii || i i |||| || I ! ! ! i I i I I I »i -v ^ ". .s H 1^ F-B SCALE ->-) s COMPARISON OF FORMILAK. F = 5 inimnes. F-B -r-l" 2 i .< i 4 AM.rn.v Al'prnx. .\l>-*o!ute ■54" IKI 5.1 IMI 52 (HI 51 IKI 50 (Ml 4'54^' 12 5.Mr. 52 -21 51- 2ft 50-51 Tlu' nii)f.\. (.omt'iiifiil im'thdd of (lfii\ing tlu' lorrt'iU'd mean reading is dial suiiplifd liy ilii' "Abacus for C'orri'ciiiiK Micrometer X'alue for Frror of Run," tii; '>A. llie meliiod of procedure liein^ as follows: 1. For each microscope, calcuhue llie mean value of F, of B and of F — B. 1. Locate the value of F on the central vertical line of the diagram. ?i. If F— B is positive, iiroceed (lias;onalK- downwards to the left until the value of F — B is reached, and then proceed horizontally to the central vertical line and read off the corrected mean value. 4. If F — B is negative, jiroceed diaKonally U]nvards to the ri^ht until the v.ilue of F — B is reached, and then proceed horizontally to the central vertical line and read - comenieiit method of deriving tile corrected mean reading is that supplied by the "Nomogram for Correcting Micrometer Value for Frror of Run," tig. '>B, the method of jirocedure being as follows: 1. For each microscope calculate the mean \alue of F, of B and of F — B. 2. Locate the value of F — B on the F — B scale. .V Locate the value of F on one of the five F" scales. 4. By means of a straight-edge iiroject tbt line joining the two jjoints — I)oint F— B on the F-B scale, and i)oint F on ,! > F scale— to cut the -orrected mean value scale; when the point of intersection on this latter scale gives the corrected mean value desired. This nomogram was calculated from the absolute formula and conseciui ntly apiilies to all re.ulings irres])ecti\e of tluir magnitudes, giving the result correct to ,1 fitth of a second. Example: Mean \aliies of F aiu 1 of F— B an- found to be 2' 28"-0 and + ,V' 5, res))ecli\eiy. Required the \alue of F corrected for error of run. This is found to lie 2' 20"-,?, as indicated on the noniograni bv the broken line. It should be noted that it is not necessary to draw any line on the nomogrdm to obtain a solution; all that is iiecessar\- is to lay a sir.iijdit-edge on the norno- gram so as to touch the two points indicating the gi\en ilata, when the point of intersection on the left hand scale at once gives the corrected mean ^•alue. The left hand or corrected mean \alue scale is gradu.ited in seconds only, so that onl\- the seconds of F are changed, excejit in the two following cases; ia) W'iien the solution obtained on the corrected mean value scale falls ,ibo\e 60", increase the minutes of F by 1'. ;.';) When the soUiiioii obtained on llie lotieCletl mean value scale tails iielow 0", decrease the minutes of F b\ 1'. 23 MU'ROSCOPIC ()HJK( ri\K. Thf ohjic ti\i> ()2. tig. 8, moiiiilid in it> ixW 6,?, is siTi'SVfil into ilio lube 64 which in turn is pcTnianunily stTi'wi-il into the draw uibe (>5. Two pins 06 pri)it' turning tlu' two c.iiisian nuts 6'). Tlic objcctixc ina> be cenlered by tlirninji the ca])stan ring 6iS. MICROSCOPK REFLECTOR. -A i)laster-ol-I'aris reflector 70 n.omned in a tnetal tube throws an e\en, soft hjiht upon liie jiraduaiions of the horizontal circle. Tiiis retleelor is cai)able of rotation >iiioitt the axis of the microscope, thus permitting daylight being itsed wlu'ii liie rellector is turned outwards; and artilicial light, wiiich is sujjplied by means of a small iiic.uidesciiit electric lamp, when the rellector is turned inwards. As the plaster-of-Paris retlector jHissesses a white malt surface, the horizontal circle graduations, when \ iewed through the microscope, appear perfecth' black tipon a sil\er>' or white surf.ice. and there is no metallic glit ter whatexcr. MUROSCOl'E M.\C.NTFU'A'rK)N. -The im.ige of a five-minuie interval, which s])ans ()■ 004654 of an inch, when projected tipon the microscope dia])hragm spans a space co\ered by one revolution of the niicroineli'r screw, or one forty-t'ifth of an inch. The magnification of the objective is therelore eciti.il to ,', di\ided by 0-004654. or 4-77 diameters. As tin- distance between the held and eye lenses of the eye-piece is about three-(iitarters of an inch, atid the focal length of lach lens is aboitl one inch, the e(iuivalent focal length of the eye-piece, ff divided by (f + f —a), is OSO -nch. Therefore the ntagnihcation of the eye-piece is lOO divided b\ OSO-- I .' ■ .> diamtlers.* '!"lu' magnitication of ihi' microscope is then 4-77 X 12-5=60 di.imeiers — ne.irK-. tLLlMINAriXC. THK 1.1 MH. Illuminaiion of the limb, when day- light is not siitVicient. is obtained by small incandescent electric lamps |)ro\ided for that piirpose. run off a batterx' and controlled b\ means ot a rheosuu which \aries the iiilensil\ of the light. It is necessar\- to see ih.U the reflectors .ire lurned into their proper positions. rin' same result is acliie\ed in the d.iytiine by turning the reflectors outward and utilizing daylight. In places surrounded b\ trees and othir obstructions to light, the limb is a])t to appear dark and indistinct. I'nder these conditions the illumination ma\- be improxed b> reflecting the light from the sun or sk\ onto the reflectors b\ mi-.uis of a mirror or a slu'cl of whilt' pa|)er. the lu'ld book, for instance. In all cases it mu--l In- borne in mind thai the light reflected oiuo the limb shoulil be. as nearly as iiossible. radial. The effect of ha\ing the light strike the graduations from eillier side is to m.ileri.ilh .liter their apii.iri'iu ])osition~. thu-. iiualidating the micrometer readings. IllK I'KINCllM.K or MICROSCOI'K AI MISTMKN I". the arc measured b\' the microscope of this instrumem is .i space of the \alue of tn e tninuu's. which is the sp.ice coxered by tlu' run due to one ri\oluiion ot the micrometer screw. Now in order that the mi( rometer screw ma\ be compeieiu to measure a li\e niiiune sjiace without excess or defect, it is clear that the image of the latter musi be magnified so as to occup\ preciseh the length c(Aered b> one rexoluiion of the screw. Suppose that an object, such as the di\ ided limb of the circle for insl.nice. is jilaced exactly at the stellar focus of the object lens; then the r.ix- passinu thn>uel! the lens become narallel, and the image is formed at an infinite ♦III II ini li''^ i- ;i— uini'.l to 111' till' ifi-ititiii' iif ili-tiiirt visliin dir tin' uli-itvri'^ 'yi'. (liMaiKf. Bm i( il \>v placid Ik'NoiuI iIr- >ullar focus, an imaRc is fornu-il within llii- uil)c, and ilic i\\i> poinis where the ili\i intake from the same lens he calleil V. then the length of the imagie will exceed that of the ohjecl in ihe ratio K.f. or F f will lepresem the maKiiitied state of ihe iinasie. Hence it is clear that the expression F f will have an ii'creased valtie eitln-r when F is atiKmeiiled or f diminished. This is the fiindamenlal princi|)le to he attended to in adjiisiing the runs, viz.; If the ohj'-ri glass l)e ])rotriid(d, it will approach nearer lo the limh wherehx the size of the image will he increased, and will re(iuire more traverse of the micrometer screw of the micToscope to measure it; and this will also he the case if the whole microscope he inade to ik^cetid towards the limh. l'( ADFl'lONS OF ADjrSTMKX'r. -Before descrihing the method of performing the ailiustment, it may he necessary fui^ther lo premise that the microscope is in lorrecl adjiislmeiit when the folh-wing conditions are strictly fult'illed, ^iz.; when (he image of the divided limh and the micrometer lines arc- so distinctly visihie together that no parallax can he delected hy v.irying the lK)sition of the e>e, in which slate of good \ ision one rexolution of the screw miiM exaciK ineasme one of the five miinite si)uces of tl e limh, of two revoluti(»ns measme two five minute spaces. FLIMINATION OF I'.\K.\F1..\X. -If, on removing the pai)er used in focusMtig the e>e-])iece, the limh is not visihie, the tnicroscope nitlst he moved hodih up or dowti hy means of the capstan nuts 2. It can easily he fouiid out whether the microscope reciuires to he lowered or raised to produce distinct visioti, hecaiise. if. on screw ing-in the eye-piece distinct vision is ohtaineimuh.lneou■^ly with the micrometer lines, bring one of the graduations to tite centre of the tiehl, and MiiKrimiJOse the micrometer line> upott it. Now mo\e the e\e to and In, ,md if the image remains slead\ there i> no parallax; htit if the graduation ,il)l)ears to shift its (jlace relaii\el> to the i.iicrometer lines, then tiotice in which direciiim it moves and correct; the p.irallax 1 y raiMUg or lowering the microscope, as the case may he. .\l)jrSriN('i lllK K( N. Ihe microscope h,i\ing thus bei'ti freed from l)ar,Lllax it will be necessar\ tiext lo place a gr.iduaiion of iln limh, 0° for instance, tmder the centre of the microscope, and then measure with the micrometer the sp;i( e belween .S.SO° .^.S' and 0° ." If dtie care be taken to note the wa\- in which tile gr.idtiaiion oti tl.;' micrometer drum runs from 0' to 1' to 2', etc., it will b>' fotiiid that otie cut or stroke, .^5')° 55', will be arrived at by revolving the micro- meter drum in the same direction as the ntimbering on the drtint; witile the other stroke, 0° 5', will be reached l>\ ;i moiiMU of the micrometer cotitran. lo the onler of gradualion. Siihiract the reading of the l.ilter from the re.iding of the former, and ihe difference will be the number of minutes and seconds measured by the inicro- nteler. If this f.ills short of leii miniiUs. the magiiif\ii'g i)ower is too Mitall. aiid Ihe object glass must he protruded 1)>- means of the cip^um mils 6'), fig. 8. in order lo augmeni lb'' image; bill if the measured inler\,il i-xceeds ten minutes, the object glass mu,-l he raised to diminish the image. \iiw in the fi'-rntiT c:f^:\ •.-.roi rndiiig the ohiecl, ghiss will titrow the iniaiie higher up ihe microscope, .uid produce near jiaralhix to correct which the whole 25 mi.n.>a,pe must he move.l a.ain hi^luT up an.l UnUvr Iron "-■, ' • ;^"^, ^ again wit diminish the- run so tiial the hrst .-..rrectmn .h.,ul.l l-e a '" '7'\';;' "^ o .„unuTa,t the sJ.se. nl a.ijustnient lor para.las: an.l he who e pro ess u' t e repeated two o, hree times until the two n.utually tntenlepe.t.le t " m.liti- as, eorreetness of run att.l freedom front ,.arallax, are very eloseh saiisl\..l. 1 rRrUKR PRF(" M'TIOXS. It nutst i)e reineiiibered, however, thai Ihe tlivisions of the limb are thetnselves affecle.l l.y errors of sradualion, to ehin- inat the effects of whieh it is desirable to take a tnean o several U-n tt ...t.te s a es Moreover the plane of the eirele ,na> not be exactly at r.^h a'.«les .., the avis of rotation in which case all t.arts of the crcle wnl not b. at the sam. istwefmin the object lens, and there will be a .litference ot run occastoned he circle ap,,rnMmati..K tte.trer to, or recediug farther trotn, the ,n.cros.-o,,e. ? is also t.. be re,ne,itbere.l that the excellence ol the ob..rvat,ons d.p.a.ls not on a single microscope, but on the joint oper.tUon ol the two; so ; u a hes have l)een diMuantled, or taken off for the purpose of being cleaned .,r tor any olhei" s.m.lar re.i^-.n the a.litistments will be found alrea.ly near to the truth, a.td all that ,s re.iuire.1 is an alteration occasionally of the run of a single microscope, so as tx. • mpensate for the errors of both. Now. as the value of one m.cronteter has t e veiglu of onlv one-half in pr.Klucing the mean, therefore the correction to be apnlied to aii individual microscope must amount to twice the mean ol the errors of the two microscopes or simiily to the sum ot the two errors l--or instance, if the mean value of the two nucrometers amounts to 1() +6 for a' 10' interval; then 2X6" = 12" is the correction to be applied to a smgle niicroscope to .educe the mean of the two to 10', and this correction is much more easily applied to one microscoi>e than is a smaller correction to each. ro OliT.MN THE MEAN \ AHE OF ALL RINS.-The method to be used is as follows; Set one microscope to 0°, so that a degree stroke will tall nearix tinder the notch of each microscope. Now as the micrometer in obserNing is limited t.) .m excursion of 5' on e.ich side of zero, it is unnecessary to go beyond that extent .m either side, ll is also unnecessary to re .d the .legree stroke in the notch, because the sum of thi^ 5' spaces will be giv. .. at '"u-e by the re.iding of ihe extremes; conse-iuenth it will suffice to ineasure the 10 space tiidcT each microscope, re,)ealing each measure several times lor the purpose of nulhU - ini: errors in setting. „ . . , Now turn the instrument to W°, mf and 270° m succession, and measure the 10' M«ces in each position .is bc^fore. The ntean value of each micrometer will thus be obtained from the mean of the four 10' spaces at each of the cardmal noints of the circle, and therefore the mean Nalue ot the runs of the two micro- scopes in combination will be obtained from eight independent .-^ spaces, which is sutticient. ,,, . ,,,, If the omibnied errors of the microscopes amoiniL to more than J. m 10 , it will be .idvisable to correct the microscope which is most ernmeous t)v a .[uanlitv equ.il to this combine.l error. This correction, if it be ''"b" a few s...„„.i-.'. will not retpiire anv change in the object gl.iss. because it w.ll generally be .piite sufficient to raise or lower the whole microscope uulii the leciuirc.i value of the runs is correctly obtained. 26 The rationale of this pmrecdiiiK is (hat the microscope is more sensitive as res-anls the value of the niii than it is with respi.t to para lax and distinct vision. On account of the spherical aberration of the lenses the exact nosiiion of the point of distinct vision is not sharply dehned, and vsit un a small limit the run may he varied sensibly without producing any aiipreciabie parallax. This iiecularitv will, iwrhaps, be rendered clearer by apiilyinn numerical values to the expression F f which represents the maKiiiheil stale of the linage. Now F f eduals 5-7 M; and let the microscope be raised 01 of an mch, which will make f equal to 1 ■ 11 inch. This will reduce the imajje at the focus in the ratio of 5-2-5-l.S in which ratio the run will be affected also. ( onse(|uently, because 5-2 5-15 eciuals MW 2')7, the run will be reduced by .V. Therefore the descent or ascent of such a microscope will produce a variation of .V for each OOl of an inch perpendicular change; while the latter (piantily would be harilK wrceptible in the shape of parallax. In performing this adjustment the riiles for avoiding parallax as given above should be adhered to stricth'. EXAMPLE.— The following example will render this subject ([uite clear, and it is only necessary to add that the runs should l)e taken frecpiently, and duh- recorded according to the subjoined form. In the first test the mean error was 5" -63, and the microscope most in error was B, the image being too small. Therefore this microscojie was lowered, and as the correction to be applied was twice 5" ■6.?, or 11" -26 in all, it was endea- voured to make this microscope read 10' by lowering it as nearly as possible bv 0-04 of an inch. When this had been done a second test was made, and the error of run was found to be practically eliminated, being only 0"-3.?. ADJUSTMENT FOR RUN OF MICROMETER T HROSCOPES Transit, T c" S 124. Temp.. 62" F. Dale, Feb. 27th. !OIJ. Observer. W.H.H. 1 9t Ml( HOSLOPK A Micijosco:'!-; B 1 ,B Kfinarks t 1 V B F'B F B F B .160" 4'60" 4'5K" '('61" 4'51" 462" g'4')" The runs were tak^n from 55' to 5'. s,H 5') SI 52 61 51 5S S8 60 51 61 4X lire 'ront or JorwjrJ rp;i iinj?* beinR tho.-*J 5Q •SM 61 51 6i 4« 60 51 61 51 62 4') t.iken when the microm-ter is turne'l in Qd" 64 6.1 (i4 64 60 50 54 52 6» 67 46 the liiroction of in.rri-in^ rea.linfis on tlif 6j 6.* r)4 5X 5.i 67 46 ft 2 61 52 66 46 int*n: an'l the ft.ji.t or hiuk-u-arj re;iflinu3 fi.S ft4 61 5! 67 4X i; 5M SI 60 56 66 50 5** 60 5 61 5« 55 67 4.< ."IS St 5<» 56 67 4') readings of the drum. J 70'' .S6 5S 61 55 61 52 57 .16 61 55 6.1 52 55 56 5'1 56 66 50 i ^7 55 62 1 55 64 SI 1 '■' 56 51) ! ■''■^ 64 51 Mr.in r, f f.uh. 51)" MS y 4« '•» l-MKll \ pan.... 9 54-17 Kiror o 1 10' rL n... 5-6i FIN \l \l)ir^rMl"Al" OV POSITION, riu' Ina^ninK oiHiaiions arc xvrv lial.U- t'n',li>iurl. tlu- lauTal a.lji.Mimi.i ..I tin- mi.T..M-..|K' h> a.liuMiiuni n v'r llu. i-r-Mur .livisi-.n i> aa.lily HU.u.l by inuv.nK .!..■ „„i,l. Inr wl„.l. puri-nM- ilu-ro is I MTiw 10. fm. X. at the ivMTM' < 11.1 "t ilu' micrniml.T l.ox. II the (. mil lKn.nv..\iniatt'l\ with llu- iioltli. .1.11 " |.-nr Ihi. inir,.n.r m-. the „.i.T.Mm..T Hi,., in ih. .vntr. c th. nntjh, a,ul InuJn I. Mtall >.r.w in ,h. oiur. ..I tlu- n.ilK.l lua.l .'); lluii, hul.l.nj; th. ;„ili;..l iuM.l staliuuarN with uik- haiul, rota., llu- drum (,(. xvth tlu- o.hor han.l until the /in. '.I, the .Iruni o.iiu-. ..ppoMtt- 1.. the mun.nu-tiT iikIcx HI, altci which liuhtcn iiu the Miiali screw. ... Tlu drnni retains its place .-nly by iriction. thcrel..n- it .s necessary U, use c.ire. wiieii workiiiK the ini.n.n.eler. not lu i.iy h<'l«l "I ll^' arately for each niicroscope: because-, on account ol errors ol graduation, readings woul.l fre.iuently be obtame.l as sh.,wn in the following examples which would (irove verv inconvenient lor registry: \ B. 0° 00' 10" 02° W O.S" .V^' 50" 10' 4,V' 1-IN\I TFSrs llure remain .1 lew other points which -hould receur Htemi.'.n' for insi,mce, n is de.ir th.n the micrometers shoiihl act m a .lirection tangential t.. the circle, therefore if during the foregoing adjustments the direction of the micromete.- sh.ml.l be changed accidentally, all that is necessary is 10 turn the microscopes anmn,! gently m the collars muil the micrometers ,„e brouuhl to act in cite i-roper .lirection, when the clar screws should be tiuhoned to render I he microscopes' positions permanent . loget tile .'mgenti.d .lirection .omcly, the ,wo paralU;! lines ol the nmromel.-r should be made p.iiallel to a degn-e division on ill.' limb. TELESCOPE EYE-PIECE MICROMETER Disc KIITION Ol- rKl.KS( Ol'F. KVK-IMF( K MKkOMKTKR. .\ front view of the .■ye-pie.-e micrometer wi,h the .'over removed is shown m Iiu 10, and a side \ iew and i)art secti.m in tig. 11. In the eve eii.l of the teles.ope .ube there is mounted, by means .. I lour small screwsllO. fig. 11. the amiular part 127, which carries the .•..hmation linear gui.les 12S rigi.lly atlache.l by six scr.-w_s 12<). he bearing IM) whul. a.-.-omn,o.lates the mi.rometer bo.ly \M. may be shilte.l laterally m a .hre. tion nerpen.li.ular to the plane of the illustration of tig. 11 by turning the twoca|.slan coll.ni.iion -crew- Ul'i- and ih.- micrometer bo.lv m.iv be rolate.l -1 this iH-armg to anv .U-sire.l angle, being brought to rest at each ninety d.-gree interval by the spring catch 71 engaging in one of the four cptally spaced n..t.hes on the ring 2S I'luiHB HI. I'r ,nt Vu'WMf Kv.';)i M rr.m -i.-r wii'i ( ' ivcr U.'iii ivr 1. I'u.ritE 1 29 l.ol.Kr 7< is ati.ulu.l lu ilu- n.i.r..nultr l....lv l.y tin- lour s, rrv - r\. Ik. 10, and „lv wl.i.h s iH.r,K,..lia.lar ... il.r axis ut ilu- ..■Kmu,,... Muv.nuin ol il, s I Vphra.n, i.„i.lr is a.n.nM-li^lu.l l.y ..p.ral.UK .!.. tuur rapstau -r.ws , xvl.il.. nia.ixv a.lius.nun. L.iw.cn the- n,i.n.„u.t.r an.l tlu' uUsr-.p. is HI., t .1 .han.i„, th. posi,i.,n ..f .lu- ri,m 72 wH nuar.l ... tl-, -!"--"^- 11. The iniir.iiiKti-i carriaKi' 77. ti«. ll>, mi.mim.ir s. rew 7») lias ..iic liuii.ln.l a.li.is.iiin llii' I'.nir sm.ill s,ri\v> ('., Iiij; suppi.i. s„pp.„-,s , „• '""^••'''''\' '■■-'; V"''., s,nAv is r...a.r.l this .arriauc' .ravels l.a.k ..r l...-.h, .h.. ,n..val.le .l.na.l h.n^ .n aiiudsi .1k' saiuf ptani' as .lu' (liapliraniii. l....s..,u.ss ..r plav l.Hvv.n, .lu- ihna.ls ..f .1.. ,nuT.,nuM.r sm-w an. ,l,na.ls of ih. .arria^O is pnv.iUr.l l.y .h. tw,. sprn.«s W. A .liaphra^.n .-t one , 'on.al an.l tiv.. pa.-alll v.r.ical spi.ler tlm-cls .s J'^J"'-' ''" 'V^Val'l h wl.i.h slips ovvr an annular proj.T.i..,, f...;-m-.l on .ho l...l.Ur -.V a.ul ^^ '^ '" pla.c- ,n,Rlv l.v tri.-.i..n. Thus .his ,liaphra«.n .n,.y \>v a.ljus.r. ... .my ..n^lc nu Iv .urnin.. xvi.h .h. lin^.Ts. A..a.lua K. th. ex.ernal en. «';;;;;■;;- ni.'.or S.TCVV an- .In- «.,„ ualo.l ^;''Ji par. l..ii,K nun.l..r.d: an.l ..nths of .h-s. par.s. ..r 'l^''^^^^"'*' '^'-V j'"" kvoh..i..n nu.v 1.C- nM.liK os.inia.c.l by vyv. 1 nv. m.lcx niarWs 8.'^ may b. usc.l ..r , kinVn'a.lin^s on .he .Irunu Vh. .nillc.l h.a.l 84 is r.^x ly a..a.h. bo first slackonod b.uk. which is Ins.oad Of .ho ...oihoil o.mb usually f<.und ..n micn.mo.ors wUi.li is londo, the c.vor may sh(.wn in lig. 1t>. the micromo.or pi.ii.er may l.e romo small screws <).). and slackeniiii; ..If .he two miows 9\. TO RFMOVK (OMI'l.F.rK MICROMKTKR FROM TEl.hSC < )1 K.- Romove iho'.w., c.ipstan .■..llima.i.m s.nus l.W, ..«s 1 .in.l 11, and the l..ur small s e-p.e2. fifteen secn.ls of lime. ..r ihr.'o minutes '"■"tv-tive sec.m.ls of arc, apart. .\ movable thro.ul 78 attached ... the .•arnajje ..t the micr..moter screw is parallel t.. the .ib..vo; an.l the wh..le series is cn.ssed centrallv a. ri^ht angles by the single transverse thread <),■!. RKl'FAl INC. THK Sl'IDKR any of the spi.Ur threads, i.r.iceed a^ THRF:Ans. follows: When necessary to replace M^ r.ikioiii iluMTiw -HS. fiK-'. 1 .mil 11.. mil iluu, li\ iiiim nw inn ilulu.nl ll.*<, llu' >liiiiitT iii.iv 1k' riiiKivrd. Hy niinivini; ilu> >i\ Mrt\\> W. liu' mvi i pi.nc may \>v l.iktii nlf. Ntxi ilu' Uvi. mtcwn "><>, 'i^. ll». .ire wiiliilr.iwii, ami itu' iwu M-nw". '>1 slaikfui'il iitl. wlun llii' miiv.ihlf ihrf.ul < .irri.iKc 77, .i^ will a- tlii' ilriim Hi, m.i\ \>v lakiti mil hikiiIut. riii> iHrmii> ilu- mnimtitiK nf .i ihdv.iIiU' iliit.iil. . riicdi.' ' ■iKiii riiii;Sl. iii.iy 1k> lifliil ntf llif hulilir 7,< Inwjiiili 11 i^ .itl.u lul,ici'i« .i llinMil uii I'.c ili.iphranm riiiK SI. il i> mi i>.>.iry lli.il the slu-ll.it lif .ipplicd In ilu- fMri'im- fv.ds of llii- lliiv.iil Diily, im ihf luwi r i)art of ilir rinK, in nnliT nut Id inttrlVri- wiili ilic imiv.ililf •hrr.iil wliidt imivi>\ii\ ilnx- In llu' ihriMilsnl' ilic iliaphniKin. DIAIMIKACM ll.l.rMIN.\Tl()\. .Xrlitu i.il ithmnn.uinn of the ili-iplnMyni i- niii, limit 1)V the Mti.ill imamlixvnt rltiirii- lamp SI, Uii. i. mDuntiil m',:r tin- tiiil 1(1, ami in lim.' willi tho traiij^virsi' axi>.. Tlie liulil Irnm llii> l,im|) i)assi's ilirniiKh .1 Mu.iU U'n>, ami al'ur lravrr>inn ilic ifnlro of ilic liollow i)i\oi, ii sirikt> uiMin the sm.ill iioli^lu'il siKvr mirror .^0. U)i. 7. moiinlid al llu' inii-r- M'clion of llu- nvo .IMS of ilii' uliscopi' .mil iiulimil .i\ .m annk' of foriy-t'no iliKrcis loi'aih; from wlu'iiir il i> rrlkrUil lo ihi- ili.iplir.i^^m in ihc in I'-pit'i r iiiiiTonR-tir, forming hl.iik lines ui)i)ii a hrijilu ticld. MAKINC. THK THRKADS MORIZONTAl. AM) VKRTICM..— Tlu' inslriimrnl is cirtfully Itvilkd and \\u- iniiromiur rolaU'd iinlil ilic ir.ms- wrsc thread is app.iiently lio.i/inital .mii the spring e.ilih 71. jigs. 2 and 11. engages in a noteh on the ring 72. Tlu mov.iltle ihre.id 78, hg. 10, is now hroiight nearly to the renlre of the field of view and carefully set so as to bisect some disiaiu, well-detiiied iioiiU. By means of the tangent screw on the ir.msverse axis clamp the thread is made to traverse this point: and if, at any p.irt of its travel it deviates from this point, the thread is not in adjustment. The small screws 76 and the capstan screws 7.=;. figs. 2 and 11. .ire loosened; the spring catch 71 and the ring 7.' held in i)l.ice. and the whole niicromeler carefully rotated until the movable thre.ul is truly vertical, when the small screws 7f) .ire tightened. The next adjiisinunt is to make the threads of the diaphragm triijy vertic;d .111(1 horizontal. Hy loosening and mining the four capstan screws IS. tiu. 10, the (li.iphragm holder 7.^ may be rotated (the screws 74 allowing it to move only in the one pl.me iHrpemliciilar to the axis of tl.e telescope) until the verticil ihre.ids ')2 are i)ar.illel to the movable thread 78. when the screws are tightened. The construction is such that when the h\e threads 02 are vertical, the trans- verse thread liragin is then moved by me.ins of the two horizonl.il capstan screws 75 until the middle \ertical thread of the diaiihragm coincides with the movable ihrc.ul. This .idjustineul .should be lepeatvd until the middle verticil thread liisects the point both before .mil .ifter reversal. M ,U-,.ni pnin. ,m.l .Ian,,-.!... ..■U-.niH. in al.itu.l. a„.l n. a/.n.ml^ U.m. . ilu , ,in, l.v .lu. .ran>v..r>. ihr.a.l au.l .lun rn.a,.- .„ m„. rum. ur IM) •I'tj"';- n,la...l un.il .I..- .ra,.>v.TM. .hr.a.l Immt,. llu- ,«..,.. I-mI, l..l..n- an.l al..r ''"'Vi .iMf.in, .,f .1.. a.ljus,inK >av«. ma> IMX.- .li«iHl^ a..... U.l .!..■ P „l ,lu. ,lia,.Uraum «i.l. nranl ... .iu- n.-...;.>1, -. ..... .. .n..N l.asr .- I" ...rmd u. liii until .ill' .liria.l-' ari' huri/unlal .mil xcrli...!. , "'•" I.ls'll ;;; a .li>...n, ,..i.,.. ,.,. ...... U,r.....U ..f an.,,... .ran.. ,.r l.-vd mav W. „M,I ui.l. ...4van...K'-. Hii. .ran... or kvrl >l.....l.l l-.' •''''''''''''",,, ,rlv llu- ...n... xrainh. liar an.l wi.h .l.r ..l-innvc fa.m« -...■ ..n..,l..r. I n.Ur .lu.. (■<.ii.li,i..ii. .lu' .ii.xiliary in.trimuii. i. .....l a. a .■..llima...r. (l)| I IMXTION I'll.' irror ..I . n i. . ..rr.i ...l l.\ >liil.in« llu' avi. ..I r.\'..h..'iun .,1 >!,.• .A.-pi^'*.' >v.un. l.> ....'..n. ... .In; .«.. ' •'•-''""r^;;^^ W). liK.. i '11.1 11, M.....U-.1 l... >'" "-"•" iiu-iIkmIs aim n.niiri'r. w ixiil.m.i.ii.n- TO MMl "^r T'lK MU KOMKIKK DKIM. Tlif mi. T..im-..r .Irum 82, i„. 10. i'.r.V.a...! until /.■... ......-■. ..pp.,.iu. .!..■ ^'"l^\ ^''-^'^ ^'.JZdrZ in ,1h. ..'n.r.. ..f .lu' tnilU'-l I1....I S4 i. 1. .....■...•.! ; ...» .lu". l-'-.l-l-K ' ''^" Ma.i......rv. .!,.. mill...l l,..a.l i> r...a....l .....il .1..- .-.-va .l. . ,..•...1 -> ^'M- " l-.< up..n tiu'mi.l.llr N.r.i.-.tl .l.r..a.l ..I .!..■ "^"^ _ ,„m,...r .S6 r..,.,t...l un.il /.ro ....ncs ..pp...... 1 ..• ...-l.x ui.trk S. ; ^;l"' ' "^ ^^^ ar.. .inhu.n..l imiil .lu' .'..uni.T .■..t;..^... ^^nh ,!..• ^v.n ,H.< I.h.mK an.l xM.l.out uu.lui- fri.-.i.).!. . , ,• 1 • ; ,,<,.,. .ml |„ m.ikinn a la.itu.lu ..l...Tva.i..n llu' l.-nv; .l.aKnn..l .•>i-p....- •> U...I. . iw ,lu. U.U-.-..P. i. nc.arlv v.-rti.-al. lu.U.r .!,.■..■ .•.,n.l..,.m. U.. -In.n. ..... ...mu.r ma'v 1... r..a,l !>> i.i.l.x n.ark. M.uik.r u. S. a.ul H,, l-ut ^^Xtuun ..p,..,.i,.. .i.l... In .Lis .a.... .lu.r.l.,r... it .. -Lvu-u. .hat ;vs th.. l-a.W -.u fr i.l.lx .u..rk> S5 a,r half a r.-v..h.ti.... ..part. .h. !'; .r. w.l' ■.-. r..: • '^ > \\^ th.- m..val.l.. ihr.-a.l i. st.p.ri.up.....! ..p.... ih;; •"''''"^^^■' '''■', \'''^,: ,,,,1 v .liaphraK.u. 'nu-r.-fon. it i. ,t..-.-..ary t.. r.a.bt.sl th.. <1™''V^''^ \ ', " '• mean. <.l .!..■ La.k iu.kx ni.irks, vhi-h ntay W iUmv a. ..Ir.a-ly .xplaincl. Ml-THOl) Ol- RK.\1)1N(. MIC KOMKTKU. S.. h.ni; ... tlu' muv..l.le ,hroa.l i; ... .h.- 1.1. ..f .1... mi.1.11.- thr.a.l ,.f .h.- ''••'l''i;f '''• ^'''/'''IV/^liil^^' Z" ar.- rea.l .•xa.-.ly as in.li.-..t..,l by .lu- tn.l.x ,n..rk.. In... ... U^, , he . it K is 1<): t^ r.A-..luii..n>. When. h..xv..v.'r, the m..vai.U' .hr.a.l .. t.. .he '''."'' ,h. uti . !!.■ .hrea.l .,f .h.- il....' ill. lie.. ..'.l I'V .he .-..unter. draw l.il.o Vhv ..aU- if ih.' fi.eal 1 Ft FSCOl'K l-OCrSSINC SCAl.K. A. the ..hje.tiv.' eii.l ih. . arrii-. a .m.ill s.al.- whi.h sli.le. over a /en. m.irk ..11 the mam tube, i. Kr..; on .his scale Ik- itole.l. il is an . a.> m.i.ur ... m. .he lel.M-..p.- aji-nn to this l.icn. a. an> subs.(ill.'iil .iiiie. STKl I \R KCKIS. C.rre.-i f.,eus.ing i. nio.i imp.. nan. ft.r ..11 .is.ro- non.i.al ^^utk. Indifterent fo.t.ssins may easily inv..lv.- the l..ss ,.1 <>";' "'i;^"'- lu.le in slars visible. If the .orre.-. iM.s.tl.m ol .he .Iraw tube tor s.ellar to. us be not known, it nia> be iktirmiite.l as f.)llows: 32 [f4 I lulls approxiin.i ■Iv 1m)i1i \\\v ohifit kI.ihs and ilir prismatic •■yt-iniff A lit lit- hcforo Min I'lilc Star .in iMt 1111 .1 il.iv wlu-n llu' ilir i> li'.KJN , (liri'ci llu- tflrMopv III! ihf I l.iMCl it l>v Itu' miiidir vcriital tlir.ad. If llu- star remains l,is,i-l.»■ is niovi-f .lu- i)l>ii-it «'•>''> ... ■ i • f If llu- star a))iH'ars to movr in tlu- siimi- diri-itum as tin- i-yr. thi-rt- is lar parallas and llu- obj.-. I tjlass musi l)i- rnrkfil in. If. on tlu- (Ulur li.md llu- si.ir a,„H-.iis K, nu)vi- in llu- dini m- n nwtniry U> ihi- i-y.-. ilu-ri- is lu-.ir par.illax, .iiul llu- (>l)ii-.i kKiss nuisi lu- w<>. l.ruuiiht int., .orri-ct I.HUs, nou- llu- n-.uiiiiK on tlu- small siali- on th»- sidi- of tlu- U-k-si op,- tii u-. Now .uljiisi llu- lyi-pii-.-.- until iht- star apin-ars .is a vi-ry tiiu- and l.riulu '"'"ilu- sull.ir locus for llu- mi.ronu-ti-r ihri-ad must l.i- ditv-rmiiu-d in.U-iK-nd- .-ntlv .111(1 in tlu- sanu- ni.miur. llu- ditTcri-nii- in sc.iU- ri-aduiKs for t lust- two toii'lKinn ciiual io llu- axial distance- lictwccn the di.iplir.iKm and llu- micru- nu-ii-r tliri-.id. , , i i i r Su-ll.ir loi us is dct.rmim-d at tlu- Surxt-ys Laboratory and l,.c scale re.Klmn is supplied willi lite instrument. , . , . •■ ■ \ sm.ill error in selling I he telescoin- to stellar focus, which is easily made .iikI h.irdlv perceptible bv any decrease in the sharpness of the star im.ine. will c.iuse an appreci.ibU- variation in llu- v.ilue of the niicronu-ter. Iherelore a niamiifv iiiv; elass should be used wh.-n setting the telescope by scale to ste lar focus. \n error of (»-(»l of an inch in setting ihe telescope to stell.ir focus will .liter the micrometer value by 0-1.? of a second of arc jit-r revolution. MUR()MF-:TP:R VALIK .AFFKCTKD by FOCTS.-TIu- vaUa- of one turn of .he micrometer screw may be delined as the atiKk; subtended by Ihe piich of the micrometer screw, at the distance of the objective focus; and .-.mse.iu.-iitlv this value varies invi-rsely with the obj. -.-tive focus Ihe v.ilue siippli.-d with Ihe instrument is the axer-i^e value throughout the run of the iiiicr.mu-ter screw wh.-n the telescope is set lo stellar focus on the muromeU-r thread; and any variation in this f..cus will produce a correspondmij inverse v.iri.ition in the micrometer screw xaliie. , -n i When usinn the instrumeni on short sights, the focus use... u,« am -> --^^^^^ c.,uh diviM..n .^ra.luati.m runs tn.m ,.,,. eml ' '? ';S "; ^^ , , ,. ;„ ;,, ,„,(al sluMlh ami is from n lo 50 bi'iim minibiTcil. 1 lu- xiai lus luosin n ;;r;^::r::;::^;:; .:'^ r'^i^'muA h^ .>l.s.rv.a ... ^c. th. .mrror a. such an au«.c as uill axni.l any parallax in reading ihc bul.l.lc. . .- . iMii -n, ^irwli- Ic^v.l ^'> tie. 7, is mounted in the same STRinK U-A 1-- -• ; ,f^;;y ' , ' ; ,,■ .Ta out sixiv seconds lo the inch, „umner as the lai.tude Wy •>" ^^^"^ ' '^"^ is\;rav OK 1 FVFl \'\1.1H.— The determination of the Sn^r u:^,^';;;,r:;;;':;;i ,£.r9Mc.;«a ,. ^ :.. .... .-...-. .....-'- SYSTEM OK ILLUMINATION ,„^-i-iiilil rlil\ (1|- 1 WII'S. -The in.iriimml i« ociuip.."! wilh a ..i;ii;n;^i;,r:^i;iLn;;ti,.consi.in...^^^ lamps of one-quarter candle ^^^ •,j ',,",, ^ ,,1 li^ht becomes too faint, for performing all classes ol xvork 7^^'' '';,^ '"'" ';^^, ^'lad obser^•ations at and suppK in, the hght -^f -'''V {j';; ; V/, ,'s )t o each of the two micro- „i,,U. These latnps are .hs nbt UxUs^M^^^ \^^^^^ .^^ ^^ ,^^,^^^, ,,,,j ,,, -■'->■ "''•■"•'^^•'ir \, : at ac Uo J^andard hy a bavonel joint, and .s used tor tig. 7, which ma\ 34 nailing llu' viTtical cirik-; mif in a lamp holdir -U wliicli larrio ilir ivlUTiiiig mirror lor llie Wuiludc level, this lamp holder bein^; attached to a standard by a ba><)nel joint; one in each of (he two lamp holders ,M which may be attached to each of the standardsat iheendsof the telescope transverse a\is bypin-and-so( ket joints, and illuminate the diaithrasjm by sending; the liKht through a lens of about one inch focal length in the transverse axis onto the small silver mirror .W. which mav be plac.l at the intersecticm of the two teLscoiie axes and adjusted to an angle of fortv-tive degrees to each, thus retlecting the light t(j the eye-piece and giving black tl-eads on a bright held; and lastly, one mounted at the side of the microme^ r , > , ^hich may be used to illuminate the threads wheti observing fail, u-v-, so a- lo -'ve bright threads on a black field, as an alter- native to the bo\ c BATTER .'. riiesv l.iiiT s are run off a battery of two, three, or four of the four cells supplieu, a..... •; il;.oe volts being ([uite sufticient. The cells are ol the semi-dry 'ype, that is, they remain inactive until filled up with water; but after being filled with water they remain active until worn out. The battery of four cells is in a wooden case with metal carrying handle. This t>pe of cell is \ery much superior to the ordinary dry cell, possessing higher voltage, greater amperage and much longer life. VOLT-AMMETKR. — A Kent pocket automatic volt-ammeter in a leather case serves to test the single cells of the battery so that those w hich are extiausted may be replaced. To make a test, hold the instrument in the left haiid with the thumb over the button, but not pressing it; rest the plate marked "Carbon" on the carlxm of the batterv, which is the centre terminal, and ])lace the end of the fiexible lead cm the zinc, or the outer terminal. The voltage is then indicated on the lower or green scale of the instrument. To obtain the amperage reading. simi)ly press the button, without changing the positi(m of the meter, and the indic.ilion is on the upper or red scale. It should be carefully borne in mind that when the buttim of the instrument is pres>ed to obtain a reading of the amiseres, the cell is short-circuited, aiul should this condition exist for an'/ appreciable time, it will result in the destruction of the cell. When the cells are in good condition they should give the following readings, approximaieh', when tested: 1 -5 volts. 1 2 am])eres. RHEOSTAT.— The rheostat and lamp leads are shown at 22. fig. 7; and longitudinal sectiims .ind switch positions are given in fig. 12. This rheostat consists of a coil of forty-two turns of .No. 21 B. (S: S. gauge Cerinan silver insulated wire '/8, wound U|)on a vulcanized rubber core W, the whole being enclosed in an outer brass c.ising upon which travels the ring 100 supporting the c(mtacr sjjring 101. The contact spring is held (mt by a sm.ill screw, and slides in a groove, the insulation of the wire in this groove being removed so that any proportion of the resistance may be utilized l>y sliding the ring to the proper ])<)sition. One end of the rheostat resistance wire is led down inside to the clamp 102. Wires front each of the pairs of the three lamp leads, as well as the neutral wire 10.^ from the other three wires of the lamp leads arc also brought down inside; the three lamp wires joining KM Joining onto the clamp 102. .At the bottom there is mounted the switch ring lO.S which carries the switch 106. This ring can be rotated to bring the switch into contact with an\' oni' of the three contacts 104. 92.?05-3i.J 35 ■!■ loa 105 mr. — -[<\^s 104 A iii-J KuiiHE V2. I.MnKiiu,Uiul Sctions ,in.l Swilcli IN.-itinn- ot lUicosmt. i6 Thf rlK-()-;tat alTonls a means of selcctiiiK any onr ol thf thnr lamps lor illumination, ami nmilaiinR tlu- intensity of the light supiilad t)y this lamp. Sli.linu down the rin^; coiitact-makcT increases the resisiaiue and . and' in order to prevent mistakes it is prtlerable to turn ih have the transverse thread vertical, instead of the usual live parallel tliread.^ DIFl FCTINC. THK LINK. -.An instrumental method of laying olf the angle of'detlection of a base line at a township corner is afforded by using the e\e-i)iece micrometer. i ■ i ii In Hat countrv, place the movable thread at a distance trom the middle threa.l of the diaphragm e(iual to one-half the deflection angle and direct the telescope to intersect the back picket. Then place the movable thread al t he s.ime distance on the oi)posite side of the mid.lle thread, ami use it to set the forward picket. In sloping country the detfection angle must be multiplied t.y the cosine of the angle of inclination. TFI FMFTRIC MF.ASIRKMFNT OF DISTANCK. -The angle sub- temled bv a divided rod held vertically or hori/cmtally can be measured with the micrometer, .intriinifnt ;is inlin.lril lor ()lisfr\iiis; .i/iimitli i> >li<>\vii in rii;>. ,' and 4. W'luro tiu' iiroiinil i> soli il nia\ l)r nc'i\'>sary to faiiniL; towards the star \vho>e a/iniuth is to be ohx-rxed. For ease in lexelliii^ il is ad\i>,il>le to lock the instrinneiit in a p(»''ion such that two of the levellinsi screws ari' on an i'asl-aTid-\\e>t line, : .e thini facini; towards the north (jr south. If ol)servinj( oti the horizont.il circle, the e\-e-piece micron .i ■ is turned to tirin^f the transverse thread \ertical. If ol)ser\inj> with the e\e-piece niicro- iiuter. the micrometer is turned to lirint; the transverse thread horizontal. The first case is illustrated in fit;. A, and the second ca>e in fiit- +• it is customary to make all azimuth ol)>er\ations durint; the daytime, when natural li^dit is (luite sufticient. If the lii;ht should be poor, however, owinj; to surrounding trees or to a dull sk>', the lamps on the horizontal circle mav' be used with advantat;e. This nece>sitates connectini; up the batteries to the rheostat by me.iiis of the batterv" leatat leads to the pint; on the horizontal circle, the rheost.il beinji supported from the phnnb-bob hook, or from a iripod lei; i)in. The tvvo lamps on the horizontal circle are on one circuit, and hence they are both illnn'iiiai d at the satne lime. Should the batteries be weak, it ma\ happen that the tw( lamps cannot be operated lonether satisfac- torily. In thiN case the himp not re(|uired ma\ be " plu.t,',co|)es. 'rhi> applies to angles of ain size. 2. Reading the angle by the eye-piece micrometer. This applies only to ?mall angles King near the meridian. ,^. Reading the angle between the merii;r.ii»hi( ;tl Sur\'-ys Hr.tnih. Drp.inniiiu of tit'- Inu rior. Otl.iua. 38 Tlu'ii inaku an ariuralc selling "" ^'n- star l.y nivalis ot uiu a/munli tani;viii MRW llu- hi-iction DiiiiK mack- l>y a MTtwiiig-ui) n.laiK.ii; .iiid note tlu' tunt; ol l,i,i(ii(.n <,n iln' sidtroal chronoinitcr. If tlu' star \w nuar culmination and .novniR rapidlv. i.:a( A thi' ihnad >liKhllv in advance, and note the innc of transit. Read the striding U\cl, llun reverse it on the pivots and read it again. Alter the second leading it should be removed altogether. Kach of the micrometer microscopes should now he read three times on l)olli ■ilie forward and the backward di^ isions. . ,„ , ■ • ,, ,?. Transil the telescope, reverse the instrument 180 degrees in azimuth, and repi'at 2. \ ((mipieti- i)l)ser^ation as above, under favourable conditions should give a resiilt correct to within a xery few seconds. Thi- is clearly shown in the following specimen observations, the individual results 1».'1"K: 1st observ.ni(m 3?9 .-.'J jy 2nd " ^V 3rd " -^',, The maximum deviation from the mean has (he small value of l"-0. OUSKRVINC. AZI.MITH WITH EYE PIECE MICROMETER.- It is assumed that the sidereal time is known to within a minute or so. ll is als(i a-sumed that the position of the observing station with respect to the system ot surveys, and the approximate directiim of the meridian, are known. 'I'he following programme is the one usually adopted, see hgure 4: _ 1. Point on the reference object, tighten the azimuth clamp 11-^ set the micrometer thread at a distance from the middle thread of the over the micrometer thread hv operating the head 118. This adjustment ser^■es merely to bring the micrometer thread into the centre ot the held ot view. anU does t'lot in anv wav alter the reading. • i i- i i ' The altitude of the Pole Star is obtained from the .AsLronomical Melil r.ibles for the sidereal time and place of ^)bser^•ation and set on the vertical circle When this is done, there is no difliculty in perceiving the star. Next place the slritling level cm the pivots with the zero of graduation lo TJien make an accur.ile bisection of the star with the micrometer thread by uirning the head 84. the bisection being al\\a>s made 1)\- a screwmg-up rotation. Read the counter and drum anil note the lime of bisection on the suiereal chronometer. If the star be near culmin.uion and moving rapidly, place the thread slightly in advance and note the lime of transit. Read the striding level and re\ erse it on the pivots. Then repeat the bisection of the st.ir as before. Then read the striding leAcl again and remove it. ^ Set the micrometer thread in the svmmetrical position on the opposite -i.le of the middle thread of the diaphragm, transit the telescope, set it to the altitude of the star, reverse the instrument 180 degrees in azinuith and repeat i. .\ comXte obser^•ation as above, under favourable conditions, should give a result correct to within a ver> few secrmds. This is shown m the following specimen observations, the individual results being: ^ ^ l.-t observation ^ 24 33 2nd " -^2 .^rd " H 4lh " '"'-''„. The maximum deviation from .... mean has the small value of 0"-7. 39 m SI'B IMF.N A/IMITII OHSKKVATION" Place ^.M C^S. /^ p/^Z/.^C^rj^K. /j^ T(.o.66.5>4 ,, ,^„... r - ,../l...', , , Da,. >y^/y S, /9/J Observer >^/^/7<'/<:/'2v One turn of niicrometer 'QP-.^A One division of sthdinK level ^■r<'r Chron. Time MuromPter Readings Level Polans R. O. W. E. Corrn. /Z* /9'" 37' 28.5 /O.O 9 3 29.3 '/5./.9 ^/3.5 -20.0 -3" /Z^ /Z" 38^ 29.0 /OO 9.7 293 -0.6>./.9 ^/9.0 -796 -/" Circle Kight /^/ /^/T. jyS y 47 Circle Left /Z^ /Z'" 38' ^ 47 /Z ZO Z4 / Z7 59 /Z /3 Z5 / 27 39 /O 5Z Z5 763° 06' /3" /O ^5 26 /£/' 2/ 30" 2. 30653 0. 79995 7.98084r7\ Z.30653 0.27273 7.46334 2.30653 O. /9995 /.97660n 2. 30653 O. Z727 3 /. 50467 2.48732^ 1 Place 2. 04260 793636^ Z.48308n Z. 08393 /. 98699^ 2.02946^ 5.3/44/ 2.07092 ^ 5. 3/44/ 3. 34387 /7 3. 38333/, 359° 23' 73 36 (79 339' 79' 32' O 40 03 3S9 39 ZZ 339' J9' 29' 359 39 37 >?1 41 Sl'i:( IMFA \/,IMI Hi OBSKKXATION Place 9.S0c/?^. M cr /V £, cqnsec. / ^. /O/'/SS R. 066.94.. , - , ,,/^ „ ^ n^xt^ty/y 0,/9/S o\>^xsttyA./'/ef<^<:r /P.A.S. 0. at P 0. Horizontal Circle Readings Reference Object Polaris Microscope A Micro. B Microscope A Micro. B 51 1 2 3 /79°59 F. B. 0/ F. B. ' /79'3d F. B. ??' F. B. /6 /3 /5 /6' // /7 32 33 3/ 33 33 32 36 34 34 35 35 35 /o // // Mean /79'53' /6^ 0/' 32:2 /79' SO' 34:7 33' /a'4 5 ! a 5 1 2 3 3S9'J9 23 23 23 26 25 26 0/ 34 33 39- 36 56 33933 36 39' 36 59 36 39 36 26' 25 27 26' 26 27 Mean J39'J9'^S'4 07-34.^ S39'S3'^4 36' 26.7 Mean H C. R. Level correctio of Pol Circle Right /73' 3/' 33" - 6 Circle Left 933' S3' 72" ^ 6 Mean chron. time Chron. error Sidereal time R. A. of Polaris ( in time ( in arc Log tan P Log tan & sec L Log cos & sin ( Sum Corrected H. C R. of Pol H. C R. of R.O Angle Pol. to R 779 S/ 47 /&0 (Xf 34 339 93 78 S60 00 40 28 47 23 22 Pol. from collimation loj-. One turn micrometer log. Altitude Pol log. see. Sum Pol. (r. coil, red Level correction uced to horiz'al.. Microm. angle ■■ol. fr. coll Log 7 R. 0. from colhmation log. One turn micrometer log. Altitude HO log. sec. Sum Mierom. anj;le K. C). Irc-n coll Anglr Pol t.-. R Direction of defler tion Log a f sees.; Azimuth of Pol. Angle Pol. to R.O. Azimuth of R. O Mean Convergence Bearing olR. 0. Amount 1 1 M ()\ IIOKIZOMAI. CRCI.K. Inttrament 7,<^y3. f2f One turn of micrometer 'QPr2.2 One divition o( striding level .^f-^/^? Mirrometer Reading* Level Polaris R . O. W. E. Corm. /2^ 33'" 38' 28.6 //.6 9.5 30.2 -3./^/. 9 i-/7.6 -20.7 ■6" /2^ 40"' 04' 3/.0 /O./ //.8 29.4 ^3.3>./.9 ^20.9 -/7.6 ^6" Circle Right /2^ 33^" 38' ^ 47 Circle 1 j-ft /2^ 40^ 04' ^ 47 /2 34 25 / 27 59 /2 40 S/ / 27 59 //' 06 26 /66'' 36' 30" // /2 52 /66' /3' OO" 2.30633 O. /99P ^ 7.98803 n 2.30653 O. 272 73 /.364 75 2.30653 0. /9993 /. 99075^ 2. 30653 0. 2 72 7 3 /.3/008 2.4945/ n I'lace 3. 9440/ /. 98664 n 2.49723 n 3.88934 /. 93S5e n 3.93065 n 5.3/44/ 3.87590 o 5.3/442 3. 24506 n 3./9032,y 359' 30' 42" O 28 47 359' 34' /O" O 25 22 359 S9 29 355 ^'S3' 3t 7 359 59 32 43 SPK( IMIA ,\/IMI III ORSKKVAI H)\ Placf 9.^0 c/f3. /y.of /yf. cor. sec. / fp. /0/-/S-S H o 66.94 „ .. /2 Date yo/y e, /9/S Observer y. /!■ T/e^chcr ^IS. r s i 0. X, Of ■J a Mean -I -J ji e Mean Mnriiontal CitLle Kradings Relcrence Object Microscope A /75>'J9 20 20 20 Micro. B U. 22 20 2f J79\59 20.3 339^ 24^ 23 23 25 25 339 J^' 25:/ O/ JO 30 49 B. JO 49 3/ O/ ' 49.S 26\ 0/\ J4 34 34 Jg J4 34 O/' 34.2 Polans Microscope A r F. /79 47 39 39 J9 60 39 38 /79 47 J^ '2A 359'42^ 23' 24 22 22 22 Micro. B 30 24 25 24 24 24 24 3<9 £4:3 44 339 42 22:3 Mean H C. K. of .' Level correction Corrected H C. R. of Pol. H. C. R. of R O Angle Pol. to R O. Pol. from collimation log. One turn micrometer log. Altitude Pol log. sec. Sum Pol. fr. coll. reduced to horn al Level correction Microm. angle Pol. fr. coll R. O. from collim-.tion log. One turn micrometer log. Altitude R. O log. sec Sum Microm. angle R. O. from coll . Angle Pol. to R. O Direction of deflection Circle Right /79' 49' /£ - / /79 49 // /80 00 35 O // 24 Circle Left 359° 43' 36 ^ 4 359 43 40 360 00 40 o /? 00 49 49 49^ 30 4S 44' 49.0 Amount. Mean chron. time Chron. error Sidereal time R. A. of Polaris t in time ( in arc Log tan P Log tan & sec L Log cos & sin ( Sum Log -i_ / — m Log tan Z Logr Log a (stc's.J Azimuth of Pol. Angle Pol. to R.O Azimuth of R. O. Mean Convergence Bearing of R. O. 44 (»N HORIZONTAL ("IRCI.K. Instrument 7.^5. /£/ One turn of micrometer /OO'^^L One diviiion ot stiidinK level ^- -^^ •Ii' rometer Readings Level PoUn* R . O. W. 1 E. Corrn. /3^ OS'" 23' 29.7 //.O /0.6 30.0 -0.7x/.9 ^/e.7 -/9.4 -/" /2^ S5'" 38' 3/.0 /0.9 /2.0 30.0 ^2./» /.9 ^20./ -/ao .4' Circle KiRht /3^ 05"' 23' i- 47 Circle Left /2^ 55'" J3' ^ 47 /3 06 /O / 27 59 /2 56 25 / 27 59 // 38 // /74' 32' 45" // 26 26 /72' 06' 30" 2.30653 0. /9993 /. 99803 n - 2. 30633 0. 2 7273 2.97795 2. 30653 O. /9995 /. 99587 n 2.30653 0.27273 /. /3767 2.5045 / n I'Ucc 3.5572/ /. 9S634 n 2.50235n 3.7/693 /.9864/ n 3.54355 n 5.3/442 3. 7C334 n 5.3/442 2.35797 n 3.0/776 n 359' 47' 59 O // 24 359' 42' 38" /7 00 359 59 23 359° 59' 3/ ' 3S9 39 38 ^^ 1 _ 45 -• *^# (.I.NKKAI. KKMAKKS ()\ ()MSi:k\ 1\(, A/IMt 111. Wlu ii ..l.,rr\ - iiiK tor .»/iimilli. .IN in .mnul.ir iiUM-.iiniiiiiil-< >;( ncr.ilK , tare >liiiiilil lie l.ikcn, wlii'ti lllrnill^; ilii- iii>iriim»iii in .i/imuili ii\ Ii.mkI. In um' iIu' >.inu' lorwiini or li.icku.ird niuiiuiis w Inn iHrlurnnns.' thf ■..inif upcr.iiiDni in ililTtTini iil)vr\ .iiii>n>. I'his iiniU 111 niiilr.iii/c ilic iIIk i of .in> \itl»l in ihc inNlrtnntnt sI.hhI m ili.it p.irl of the inipnUt- ol ri'Miliilinn which p.i^x's duwn ihrnniili ihc Iim)| mti'W> Io the in>irninfni h,iM>. The i l.iinp mtiwn ul ich tiuiitt n the nuts of the IcviiliiiK siTcvs Nhunlil .lUv.ix^ lie scri'wcd up li^hl In tiinnn.ilc liu- ,i/riinnth.il error-, wtiich wnuld otluTw isf ni < iir. Tht' rfUrtiicf nlijfi I, which is iisn.ilK a picket, sjinuld he ,it .1 disi.mcc -nth as to he ((inivalcnl in intinil\ , sn t'.ir ,i> the fncn^ is (oncerned. ( )lher\\ise, when nliser\in^ on ihe hnri/nnt.il circle, the IiIcscoih' will he set at stell.ir Incus wluii in.ikint; .1 setlin^; on the st.ir, .md at .1 ditfireiil Incus when in.ikim; a setlinn nil the refereme nhiecl ; .md this ch.tni;in^; n| t he tn( us ni,i\ prnduci' .1 sli^dit < h.iiiKe in the line nt cnllini.iiinii. Al-n. w hen nl)ser\ inn w illi the e\i'-piece niic- rnnieler. .1 new \.ilue nl ihe nii( rnmeler si rew will h.iM' in lie calcul.iteil it the nliserv.ilinii is t.ikeii at a fm iis dil'fereui Irniii stell.ir focus. Thi^ le.id-. in ,111 iindesir.ilile mulliplic.itinn nl the wnrk nt c.ilcul.ilin^ the aziniiilh, and sn sh(;uld lie .iMiided. When oliser\iiin ^Mlli the e\e-))iece mil rometer, it shniild he remeinliered that the reference nliject must he within .ihniit oiu' lumdred miniito nt the st.ir. • is the niicronieler does not emhr.ice .m .m^;le l.trv;er than this. If till- st.ir is riiMr upper nr Inwer cuhnin.itinii. and tnn\in^ r.ipidh . iiiNiead of in.ikin^; a hi-ectinii. it i~ preferahk- tn mI the ihre.id just in fn nl lif the siar .ind linte the lime nf Ir.insit. I luler l,i\(iuralile mndilinns the telescii|)e i> i.ip.ihle of tindiiij; I'nI.iris .it aii> liniir of the d.i\ ; it will neiier.illy he iiecesr-ar\ , liowe\er, in use the liii;h IMiwer iinerlini; e\e-|)iece, of which the ni.iv;nitic.ilinii is alxiut thiri>-si\en ilianieters. St.ir-. nf the third ni.iKnituile in.i\ lie iih-erAcd at twili).;ht w hen there is stilleiiniisih liiilil frnm ihe sky for re.idiiiv; the nr.idu.uinns. Picking uji the star in llu' d.i\iime m,i\ snmelinu's he a lilile ililticiilt. A small ninxi'mint h.ick .mil fnrth nf the instrument in .i/inimh nr .iltiuide m.i\ .lid m.iteri.illx in dniilji sn. WheiuMT pn-sihle it is prefer.ihle In 111, ike the nhsir\ alinii in d.i\liKhl ; hut the iiistrumenl is eiiuipped with a cnmplele syslem nl illiimin.itinn hy nie.m> of which it .n.i> he freeU Used when il.iyliKht f.iils. As the sidereal time of ohservation on ilu' st.ir is ri(|nired in c.ili uKitiiuj; the azimuth, the error of the chronometer mii>t he known An error of one second in the linn- of ohservalion, in the l.ititiide nf the western provinces, when I'ol.iris is ohser\ed near iiinK'r or lower ciilmin.uinn, may produce .111 error in a/imuth ' larjie as h.ilf a second of arc. The chronometer error, I herefore, musl he known .\ h precision; and this necessitate> an nhserv.uion for time ilur ^ nr just nt'fore or after the ohser\ation for a/in'Mlh. The ohser\.ition for time ma\ he m.ide hy any of the methods descrihed in the >l.inilaril text hooks on astronomy. The e>e-piece micrnmeler iiermits of the instrument heinji set in the meridi.m with ^;re.ir ease. I'rnm the central tixeil thriMil nf the diaphragm nio\e the micrometer thread through an angle equ.il to the.i/inuilh of I'olaris .it tli.it tin . divided hy theseciin of the altitude, riieii make a setting of the micrometer thread on the star hy turning the a/imulh l.ingent screw. This puts the instrument in the meridian, when .ill that is necessary is to nhserse the time nl transit of one of the time stars given in the Astronomical Field Tahles. During a series nf ohser\atioiis it is custom.iry to m.ike all the individual ohser\atinns hy follnwing out the s.iiue predeterinined prograiume. This conduces to speed and accur.icy in nl)sei\ing. 46 .\~ liiilc liriic .I-' iiiiHsililf >lii)iilil Ik' lost iHtwtiii (ili-M r\ iii)i ilif rt fcniiif (il>ji'ii .111(1 (.l>Hrr\ini; tlu- star. OihcrwiM- ilurc m,i\ In- .i iiuiMiiunl of ilii- in>ininu!ii (lining tin- iiiifnal. .\1m> rare xliould l.c lakcn imi m lemch an> pari of till' iii'Iriinuiit willi llir haml. vMtpl iIkim- parl> w liii h arr alisiiliilcly lucf-sary. W'liiii liaiullinv; tlir -.triiif lt\il. lift it l.\ tin- Wduditi hanillc oiiK ; liir 'I the metal or k'-'-"' !•«• loiiclird with ilir liaiul, irror^ nia\ he iniiodnctil. I lie olis('r\atiniis arc made iti siii li ta>liioii, "i irclc rii^lii " and "cinli' litt " .1^ lo clintiiialc an\ error in tlie rollitiialioii. Coiniiliic iiistriictionx as to tin- rtdiuiioii ot the .i/iimilh ol^^er^alil>lw are i;i\<'il ill the Manual of Siir\f\>. mii-nded for the level OBSERVINC; lATITLDE SKTTI\(. II' I III; INSIKIMKNT. The iiiMnmieni a- ol)r.er\ iii^; latitude l)\ Taliiill'-- method i-. shown in |i^> 5 and (>. When the Kroiiiid is soft it may he necessary to drive in ihree htili- and moiiiu llu' iripod ,is aln.uly dexrihed. Another method is to di^ three holes hftieti or ei^hit en iilehe- deep and till in with dr> sand well r.immed. and set the iripod (eel on these sand toies. A third iiulhod is to use the stump of a tree sawn tl.il at a lonvenient lieiyht so ihat it m,i> l)e used as a pier, thi' tripod liein^; rlis|)ense(| with. rile base is rotated uniil the latitude .ire lOH is f.ieiiiK towards the e.ist, wilh two of the levelling; screws (m an f.ist-and-wesl line and the third (me laci.iK towarils the north. These eondiiions .ire iK)ssil>le U'catise the l.ititiide arc Is placed a; -) decrees from one of the velliiiK screws. The l.ititiide arc is aK inder the zito of the horizimtal limb ' 'herefore micros rnii, litis al. or departs hut sli.i;li(l\ from, the ctnlr.il posiiion. The iiisirumenl must, \>i- c.ijiahleof rot.ition in a/inuith ex.utly I.Sd decrees, and at either end of its sw inj; the telescope must lie ex.iilh in the pi. me of the nu'riilian. This c(mdition is hrounht ,il«)ut h\ means of the l.ililude slop cl.imp 4/. 1 he first necessit\ is to obtain a reference object of whith the a/imuth is accuriiieK known, .md by means of this to place a i)i(ket in or ne.ir to the nuridian. The a/.imii '1 of liiis mark is divided by the secant of its .illilude .ind b\ the valtie of ilie micrometer screw, and the micrometer thre.ul set to Kive this re.idin.u- If now the micrometer thread he set on the m.irk by ine.ins ot the ,i/imuth taiiKcnt sen w, the centr.il thre.ul of the diaphragm will lie in the lueriili.m plane. The latitude stop cl.mip 47 is now mounted rm the arc lOH and tirmlv clamped by 'he nut 122, the c.ipsian screw 12,? not (piite touchiiiK the i)rojection 124, h^. .s. Then the cajjstan screw is rot.ited until it m.ikes contact with the i)ro- jection. The telescope is now transitted, the micrometer thread set to an eipuil (list, line an the other side of the middle thre.id of the diauhraKin. .md the instrument rotated .ihout 1X0 degrees in .i/imuth. and clamiicr,. Hv means of the a/imiith t.inj;em screw the micrometer ihre.id is aK-iin superimpo.sed on the lelerence mark, md then the other capstan screw 12,S is rotated lo make contact with the other i)rojecli()ii. The telescope should now lie in the meridian plane at either extremity of its swing. The eye-piece micrometer nui.s, be rotated lo bring the transverse thread vertical and the drum in the "ui)" position. Latitude observations are .ilw.iys matle at night, and therefore all re.idings must he made by .ir.ilici.il light. This necessitates coimecting up the batteries to the rheo.stal 22 In means of the b.itterv le.ids 2.?, fijz 7: and then connecting one ot tlie rheostat leads (o the transverse axis lamp ,M , a second to the lamp 46 (m the latitude mirror holder .U. .md the third to the lamps , f.3 23 03 Of 24.570 f5.605 ^20.f -27.5 -9" 23^ 09'" 39" fO 40 75.358 .752 25.939 .933 282 4.f 4.7 27.8 ^/.O^ 7.3 23 fO fO f5.a05 25.936 ^24. f -23 f ./' Circle Kight 23^ 03'^ O/' ^ /5 52 Circle Left 23^ fO"' /O' ^ f5 52 23 /8 53 f 28 39 23 26 02 f 23 39 2f 50 f4 327' 33' 30" 2f 57 23 S29' 20' 45' 2. 30460 0.0064f f.9263f 2.30460 O. fS374 7.72952 n Z. 30460 0. 0064f f. 93463 2. 30460 0. f^374 f.70744n 2.23732 * 1>1,1CC 2. f3786 n 0. 00757 n 2.24564 2. f6578 n 0.0077 f n 2. f9343 5.3 f 43 9 2. f7349 5. 3 f4 39 3. 50982 3.48783 0'53'55" O 30 40 0'5/' /5' O 33 f5 / 24 3S L / ' 24' 33' / 24 30 92,^05—4 49 SPECIMEN AZIMITH OBSERVATION' p,,„ £^j/ P/er, 7/eyy 06s€n^<2iory, Oftayva v.. o. 6'<>///^^^^'~ ^^^^/Voyember/9,/9/2 observer ^./IHefcher O.L.5. ~ 1 ¥ Horizontal Ci rcle Readings Reference Object Polaris Microscope A Micro. B .Microscope A .Micro. B ' ^1 S. E 51 \ 2 3 F. B. V. B. K. B. ' K. B. i i Mean 55 S. E 1 2 3 i 1 Mean Mean H. C. K. of Pol Level correction Circle Right Circle Left Mean chron. time Chron. error Sidereal time R. A. of Polaris ( in time t in arc Log tan P Loi; tan & sec L Log cos & S..1 t Sum , / '-"^ /■=^. Log tan Z Log T Log a fsecs. ) Azimuth of Pol. Angle Pol. to K.O .Azimuth of R. O Corrected H. C. K. of Pol. H.C. K. ofR.O Angle Pol. toR.O Pol from collimation . log One turn micrometer log. Altitude Vo\.-46 27\of,. sec Suni Pol. fr. coll. reduced to horiz'al Level correction Microm. angle Pol. Ir. coll . R. O. from collimation log. One turn micrometer log. Altitude R. O. log. sec. O. 79 76/ 2. 22042 0. 16/79 0. 68 / 78 2.22042 O. /6/79 3. /7982 3. 063t ?5 19" 3 /6 0° 25' /3" ^ 7 0' /9' 25 20 /9 0. 6 7 OS 9 2. 22042 0.89542 Z. 2 2042 t ^.89/3/ 3. //384 Micro Angle Direc m. anglt Pol. to ion of c R. O. fron R. O etiection.. iLOll 0° /2' 59' 38 /9 O' 2/' 46' 41 02 Amount Mean Convergence Bearing of H. O. 50 WITH EYEPIECE MICROMETER Instrument I^-^S. 124. One turn of mirrometer /OO.i£. One division of stridin;- level ^- '.^ Chron. Time MiLrnmptcr Headings Level Polaris R O. W. E. Corrn. 23^ 22"^ 59' 23 £4 26.24S .303 /5.3/0 .3/7 27.2 6.4 3.7 30.0 -S.5^/.3 23 23 // 26.273 f3.3/3 *20.8 -26.3 -7" 23^ 30"" /r 49 /3.22I . /67 27.S60 .860 28.9 3.Q 5.1 27.5 ^2.7k/.3 23 30 30 f5. /94 27.860 ^25/ -224 .3" ( ircle Ki);ht 23^ 23'^ /r ^ /5 52 Circle Left 23^ 30"" 30^ ^ 15 52 23 39 03 / 28 39 23 46 22 / 28 39 22 /O 24 332° 36' OO" 22 17 43 334' 25' 45" 2.30460 0. 0064 / 1. 94832 2.30460 O. /5374 /. 66295 n 2.30460 0. 0064 1 /. 93323 2. 30460 0. /5374 /. 635 // n 2.25933 I'hce 2. /2/29n 0. 00797 n 2.26624 2.09345 n 0.008/0 r, 2. f2926 5.3I440 2. /0/55 5. 3 f440 3.44366 3.4/59^ 0° 46' /7" O 38 /9 O' 43' 26" 41 az / 24 36 / ' 24'3k ?' / 24 28 92305— 4 J^; 51 SPECIMKX AZIMITH OBSERVATION f\ict^^^/'.S'crj/yeiy(i?6serya/vryjOf^ R. o. Co/Z/ma/pr xi^i^ /^premScr /9^ /9fe observer ^4/7«?/V/^- /5 52 Circle Left 24'' 03"^ 08^ i- 15 52 24 /2 46 / 28 33 24 1 13 00 28 33 22 44 07 34/' 0/' 45" 22 342' 50 2/ 35' /3' 2.30460 0. 0064 / 1.37575 2. 3046O O. /5374 1.51200 n 2. 30460 0. 0064/ 1.37363 2. 30460 0. /5374 7.47603 r, 2.28676 t 3. 37034 n 0.00343 n 2.23064 /'24' 1 3.33437 n 0. 00856 n 3.37883 5.3/441 3. 34293 5.3/44/ 3. Z 33Z4 3.25734 O' 32' 44' 51 54 0' 30' 09" 54 18 / 24 38 / 2^ 27 The lam|)s on llie iioriznnial circk' an- used for the purpose of checkinK up the instruineiu posiiiou occasion. ilK lo see thai it lias not deiiaricil from the atiiustment for the meridian. Tliey are both on the necessary for checking ptir|X)ses, and cmall silver mirror M) should he mounted at the intersectil)lc are read, the north e!id always l)eiiig read first, then the mieroiiieter dnini is read, esiimaiiiiK the nearest te!!ii! of a division l>\ eye. This completes the obscrvTation on the first star. If the xcond siar transits on the otiier side of the zenith, the instruitieiit is rotated in a/iniuth till it rests against the other side of the latitude stop clamp. The level l)ul)l)lf should cui!ie to rest at alxmt the middle of the vial, hut should the reading ditler in.iierially from the j)revious one, the InibMe should Ik.- brought back by mea!!s of the ir.iiisverse axis tangent screw and by the levelling screw facing north, half the correction l)ei!ig !iiade by each method. The sectmd star is then observed in the name ma!mer as was the first. The vertical circle tange!!t screw 121 which !iioves the level in regard to the telescojx- must never be touched between observations of stars of a pair or group. The siK'ciinen obser\-ation is comiKjsed of twenty-three pairs of stars. It was first c;. 57 SPECIMEN LATITUDE PliUC ,U-577 (lis. \V. of NK.oir.str. .<5, tp. KIS-IS-.S. Palf Auk. i". l''l'- Ohsenrr J. .\. FIticluT, D.l-.S. No. 1 V 2 V i B. 4 B.J. B. S g;^ 6 I' ' (;rfpn . (;. » iu.j. 1«- 9 G. 10 O. II (.r.-iil. H. 12 B. B. U B. B. U r,r.-.n li. l.< !<".. 16 IB. jB. 17 B. tB. I.s (,r.--^l n. m (;r,-,n (l. 21) B. U. il B. B. 21 Grct'n 2 U.J 67.^ 451K (i7'i 4S2J IHNII 4647 7IK) 4747 ». 7(M) 474M 707 4K».' 2h*'> 7i1 4M.SK ft.U2 SOW .1161 74»S 5U7 .?IX4 .1.MH isul 5111 hl)()4 .SWiS .1614. .If, I 'J iw;7 (>147 .17 '7 .1711 •)'>'» 1 _'l)>l .><1.' X. s. N. s N. S. \. s. N. Mil KOMEIKK. KeadillK- 22-27.1 ['(..IhC 22 271 l« ()6II 20 175 20 '»20 2.1 17» 18 7.1S 2.1 1711 ig '1)7 22 421) l')..1«K l')-,108 22 ,172 16 061 25 -.107 1<»-74H J1 -615 17 0.10 24-7.18 27-7')4 1 .1 i)<)K I >0-C)7'> lis 141 : 2 1 ftdS 1X14.1 ,21 .10') 20-2X1 l|7 ■K07 i 24 621 N. s 21 25 72') 725 N. S 21 16 72«) 6X') X. 21 21 .117 ■ 467 s 21 17 ,117 -611 [.KVEI.. '14-641 j i22-5,12 1 !27 ■!').'< 122 5.12 Ditf. Z. D. in ttirnH. 2 701 .1-20.1 745 4 440 1 IHI 2 »41 .1 264 - •) 446 - I H67 - 7-6XS -I 1 7D6 - 1 '116 - 5 521 - 1 02,'< - 6-Xlt '- 7-H")l - 4-66', - .* ■ g')6 - 5 U4I) - I ■S50 - 5 (iXS 21 .1 2.1 .1 X II 11 2 2 2') 12 2') 12 d .10 lo H 26 6 (1 •X .14 .<) 10 5 10-0 2X *) x-.i 2X (I x-.i 2') O 7 -5 .10-X i).X .11 1 ') >4 2') -6 s-x 2') 6 10 12 2 12 .1 .12- 12 4-0 24-7 4 24-7 10 « .lJ-8 .1.1-0 »-) -19 -4 <( -6 . _> -.1-5 -.1-9 -4-2 X-0 .12 9 -6-7 -6 1 -5-9 -7 -.14 58 m OBSERVATION— (Tri/owr." mellwl.) Instrument T. & S. 121. One division of leivl = .V • 62. One turn of micrometer = 166" -21 7 DtALiN.viios^. Sim ami IIaikSim 4U IN) 76 S» 40 III ft5 .(0 ,S1 IH .»;-7,( III -ft' .11 55 42 IS 40 Ui S5 50 .SI IM ss so ,S7 17 42 02 05 4i< 70 4(1 '5 17 06 II 14 67 7t 41 II II 411 12 110 Ml S'J ,S(» 5(1 47 14 4S 57 05 .SI) 5 7 12 17 1 1 51 m 26 ft 7 4') ,17 51 411 52 16 56 ft! 55 4'( 07 0! .IS K6 5.1 61 S5 5') 07 IKI .IS 76 5.1 71 45 (15 4« (17 5<( 40 62 54 III 2J< 42 41 66 74 60 56 17 12 2N 05 40 6K 60 56 52 12 HI (15 56 .6H 64 12 _;7 21 54 -,HS 1,1, 64 12 51 21 05 ■HS ((2 56 47 64 41 7.'< ii M .16 t.|.4( 52. ,12 1 7 . H '. 2ft ,< \ 44 t I 4<, 1 1<) (II 7.1 116 5S 58 2'» 117 00 5(1 10 45 40 22-70 (W 2H 04 64 •1 SI 41 2ft 46.6X 51 14 117 58 IK 82 (W 41 116 58 2'( 08 ,14 20 10 116 58 42 21 17 08 81 \ 1 1' UTED MICROMETER DIFFERENi;ES 'I I'air, ,1 K O 10 IS i» I» 21 Sums finl. I KlUil"' Wvlul \(-;i.\llVh Dll-^bHKNikH, Mil riim^ ' IJitl.r.ii > 745 .1 iA4 !>**>> 1 H67 ; wtN ft »u 7 K'il t Wft H (IM \\ iuht<«l Miirotnrtpr WvlKhu 1 ill 1> -I. trim-. Pair. DilfiTf n. 1- W.lght. IJiflcrfnce ■ .— ■ ■ — . 1 ' 745 i , 2 705 J 4 . «H 1 .<'J64 i 1 iOJ 1 J • n; 1 ■«'i4A 4 i 440 i I 1 1 ■■ 7 ^ iim i 1 ; .n ft .' H»l 1 •>4I II 1,1 7'». 1 1 Tflft * ' ti IJ 1 «.I6 .' .1 ">l . : ' i H 5.5>5 J 1 1 fi*^ 1 1 H 1; 4 II 1 OiK 1 1 11.'- 17 1 1 Mrf> 2 ' 4 111 IV S ()40 J 1 4 401) m 1 l'«MI i I 1 i44 if 1 5 W*ft ' 4 J TXI 11 1 .' 7114 1 2 TII4 .«.M 1 10 I 4^ HSU Dp 45 -ly ".SI V Hn = 45 • S5S 10 .' y will rt' I)i) = \viiglii.il nic.in jMisitivr ami \h\ = " " negati\. rMnic'i r ilifffn ncf. Sinn- the sum of the wi'iKlUiil poMiiw micn.nu'tiT ilirtVri-iKL's i- eqiKil the sum ol the weighted negative mirronuler ditfen lues. am error which exist in the mierumete; i rew value is rlimiii.iied from th^ hna' mean latiliiii to av 60 DETERMINATION OF MICROMETER CORRECllON L*nn"(ii>tt\i in IS If. IS 2i. h 44 t, fth ■ «t\l 1 ■ LmI! UK^ yw \li.. \tt ,. 1)1, ^■.Slk^ \V<-U|tK«l lhl Lalllmte. Pair, 1. itmidr WVIdlii. 1. riultted ttitwlr. 1 1 '• 10 47 v| 4 07 r>'r>4 i 'i 4 11 ill 4 ')<> • 1 S 1.1 X 77 1 ^ ;i t 5'8I 1 II /. (. 11 1 All •. 4i» ft 40 1 ft 4W t, ,1.1 7 41 i ^ 4 04 1 44 ft IX i 1 4 U .. 7ft H i 1 1 1 i ■ NS 4 HI I 7.V99 10 2 .1 V\h( I.t OK l.p Li. Then 1 hte>l .11. IS 1 1 At, S s .!(> lr> II '14 1 .1(1 .14 .ISdJ IK Ml 1 1 .IS 62 .IK'dh 1 .12 1 K. .17 (.4 i 1 .17 h4 17 ■ ^7 2 1 2.'- ■».' ! ] .1 24 4.1 (1 (i() .1.^ •>4 i I .1.5 •4 11 'Ifi SI <)(l sx 1)2 74 S5 12 (17 44 S5 m) n <)4 11 ■112 ■115 4h 11 I '", II 7 5 I HH II 1)11 irss II 1)2 I 74 I S5 II 12 (1(15 I) 2') 1 ■S5 1 Wll 1 ■5S (I 117 llft.l 1 54 I 15 II 111 t^4(i 11-1)2 2.1-51 [0-433 X S|iAil_ ,,>),-„ Priihalile crnir of a MU^li' pair = ^1 ~_ \ I()-455"~X"S| 1 ' vil _ , ,y / . 1 A Prohahlc error of tmallatumk' = ^1 "i^T^I^iTS Ipl ^ CFNERAI REMARKS ON OBSKRVINC l.ATrn'DE.-Tlic level sh,,u (lin. rc.1^ ;iUras Uttl^- ^^'lav as possible after llu; imerseC.on of the s lar Sri,ee mule If the In.l.Me is seen lo be iniAinR ^vhen the reading is 1 e.ng n ui e^ "houia always be reeonU..l and the obser^•atu.n as a ™ ;:;;f "^.I'l be reie ted Creat care should be taken to avoid errors .h.e to parallax, and ^-^i^:-^::ra:=ag::'^^ E niu^^^^^^^^^ :-rri:^=r=rb:i^^^^^^^^ level n.Si,;^Ttm'fi,re. if tiuM.ailingisseen,oiWs.l-eaH^ hi nld be taken of relevelling tin instrument H the ^-"''"" " ,;X ^.^ ,n.,vement and its direetion have In-ett tioted, tl'^'/V'-''"^'" ^^ '"V ..veme^^^ „| the axis in the meridian is made nt a montent by produung a "^'>};"Y"^"' ,H h imount and ia the opposite direetion uith the levelling stre\\ fanng to'varlls ih: north Ihe bubble is then brought to the eentre of Us run In ouerating the tangent serew of the transverse axis elamp. ' is ^er^ important lo keep the level rorreet.on as small as po-s. e. or " the tmal ro„{pntati.m the stars are so arranged as '".^ ',~ ^ tt'^i^^li^f £; ^alue of the micrometer screw upon the l.nal deduced V''"V ,/„ ,!mr im e.-r r no such like arrangc^ment is available at the same tune for elumnatmg an> error 62 ill the value ni the Icvfl l)ul)l)li". Chalices in tiie temperature produce changes in the value of this l(ul>l>ie. and under changeable atmospheric conditions, the value must Aary appreciahh'. The use of the transverse axis clamp tangent screw Iiefore observing the second star is slightly objectionable, as it may be the cause of altering the strains in the telescope lube and iiroducing tiexure, or changing such flexure as existed during the observation of the first star. There is less danger in this, ho\ve\er, than in allowing the level correction to be large. When operating the micrometer and shutter heails, great care must be observed that no longitudinal siraiiH be ajiplicd. The latitude stars in the "Catalogue of Stars for 19100"* were obtained from the standard catalogues and ephemerides, anil the abbreviated names of these catalogues with their catalogue numbers are given in the "Catalogue of Stars for l'MO-0" for the indvidual stars, ("onseiiuently when it is necessary io make any adjustments during an observation and these adjustments neces- sitate the dro]iping of a few stars, those stars which have been derived from the catalogues of least weight should be omitted. The stars are observed in jiairs, one culminating north of the zenith and the other south. The difference of zenith distances should not exceed 15 or 20 minutes. The difference of right ascensions of the two stars forming the pair should not exceed five minutes, as changes ma> take place in the instrument if a longer time elajise; and besides, a sufficieni number of stars will nt)t f)o observed during a period if the stars are far a]iart. The interval should not be less than one minute, as the instrument must be read and reversed in azimuth for the second star, which will retiuire at least that length of time. Stars down to the 6- 5th magnitude may be observed with this instrument. But stars sm.iller than this or larger than the 2iid magnitude should be avoided as much ay isossible as it is difficult to make the bisections with sufficient accuracy. OBSERVr G TIME AND LONGITUDE The instrument as intended for ol(^ervi1lg time and longitude is shown in tig. 2. Where the ground is soft it may be necessary to mount the instrument as alreatly described. The tripod slioukl be set up with two legs on a north- and-south line, and the third leg facing towards the east or west. For ease in levelling it is ad\ isable to lock the instrument in a position such that two of the levelling screws are on an east-and-west line, and the thirtl facing towards the north or south. The micrometer diaiihragm is adjusted so .is to have the transverse thread horizontal and the fi\e parallel threads vertical, and the eye-piece is set over the miildle thread by operating the milled heail 118. The two lamp holders and lamps M arc mounted on the standards for illum- inating the diaphragm in both positions of the telescope, i.e.; "circle east" ami "circle west": and the lamii holder and lamp 21 used for reading the vertical circle and level; these three lamps being connected up to the three leads ot the rheostat 22 which may be suspemled from the plumb-lKib hook or from a leg pin. If a stationary- reference object of known azimuth be available, it will be jMJssible to ])lace a picket in or near to the meridian. Otherwise the aziimith of the reference mark should be determined by observation on Polaris. The azimuth of the mark which lies near the meridian is then ilivided by the secant of the angle of elevation or depression and by the value of the micrometer screw, and the micrometer thread set this distance from the middle thread of the diaphragm. ♦l'u!)Ii!ilU'rl liy till* ToiMiRratiliiral Sllr\-('ys Brunch. Dciiarttm-nt of the Interior. Ottawa, I''!4. 63 TlH- mi.r..,m-lcr Ihriacl » .h™ .ct .m llu- mark ,.,.,1 this ..,K.r;Ui..n plan, ation may be made by any of the standard methods. 64 INDEX OF NUMBERED PARTS. 1. N riws lliildiEi^; MuronRHr Kvi-pifci-. > Capsl.iii Nut> Inr Stiillinn Mirn»('i)|)f. .< (',i|»l;iii N r(W> fur ( l.mipiiii; Micro- si'opr. 4 Draw Till If ul Mi. rosiiipi' l-\i'-|'i''"- 5, l-irlil l.iiis III Mi(ni>ci.pc l'.\ r-piri <-. (> i:yi' l.cnscil Mirrcj-iippr l\\i'-piti'i'. (.lass DLiplira^iii .it Mi. r.isccipc. K.MUssiiii; Niii .if MiinpMii|H'. Kilk'itin^; I'riMii i>f \li. n>-i up.'. (iiviT 111 Kollc. lint; l'ri~ni. Nn-Hs lliililiim Tri^ni ( .ivcr. kttainini; "s.r.w nf Mi. niMiipr l.>i'- pic.i . Sl.ii ill Draw Tiilii' .il Mi.n I'.ip .if Mil ninul. r lii S. 1.^ 14 15 1(1 17. IS. \<). lU. 21 12. is. 2(). 27. 2,H. 2<». M). ,M M .U .<5 My M< .W 4(1 47 4N 4'J 50 T.ip il .1 IK'. Micr.imi'iiT Mi. riiimtir Nri'ws lliililin H.i\. N ri'Ws Ilililiiiu laiil M.IN. Diaphragm t'arri,i^;c. H.iri/.iiual l.iiHsof Mil riisciipi' phraKiii. \iT(iiai l-iiu'^ .if Miiriis..ii plirauiii- liiili'X I'l.ilr .if Mi. r.isi .ipc. Lamp H.il.Irr and l.anip I \iTli.al ("irilc. khtiisial and l.anip l.i'.ids. BatU'r> lands. I.arm' S( ri'w DriM r. Small Screw I )ri\ cr. Wri-nrli fur Trip.i.j Niils. Krv f.ir Shiftin.n Tripdil llcail. IMunili-li.ilr. Striik- SalVl\ II.iI.Ut. TclrscilH' Niirr.iraiiil Cast'. Lamp lliil.Kr^ an. I Lamps f.ir naliii); Diapliranni. Stride Level. Caiiiel ll.iir Brush. Lamp ll.iliUr ami Kelleelinis I sed in Olisir\ iiij; Latitude. L.inn Diajjiinal I-^e-pieee. Ilinh r.iwer Invertins; i:\e-piece (oxers. rrismalic Eyepiece an.l C'ljver. L.iw i'.iwer invertini; .'•■.\e-piece. Small \crlical Cirile Level. , L.irKe .XdjnsiinK I'in. Small .\djiiilinv; I'in. . Linlil Sun ( .lass. Dark Sun ( ilass Iransverse .\\i Lalilu.lc Level . Spare Lamps. . Laliliiil.' Stop (lamp. . Mottle of l.iiliriiant. . H.ittle of Watih Oil. S|iare Latitude or Siri.le \ial. Dia- Dia- Keadin^; llliimi- Mirror ind (.'lamp. 51. 52. 5,< 54 55 5(). 57 . 5S 5'». (id (.1 (i2. (i.v (.4 ()5 (id ()7 ()S (><) 7d 71 72. 7,V 74 ,() 77 . 7S. 7') SO. ,H1 S2 Ki. S4. X5. M) .H7. XS. ,S'). ')(» 'M ')2 '>.^ 'M 95 96 97 9,H 99 KMI Idl ld2 U).\ 104 105 1()() ld7 IdS 11)9 Spari' Wriic.il Circle \ial. Sp.ire riali' \ial - Lar^e. Spare I'!, He \ i.il Sm.ill liisirument Cimt. Telescope l'lii>;. Sun Shade. SIccI Spring'. Micronul.r S. r.w of Micr.isco|x'. Milled Ilea. I .if M i.r.isii.iH-. Drum ..f Mi.roscop.-. Sprini;s. ( )lije.li\i' of Mil rosi.iiK'. Ceil of Mi.ros.-.ipe ( Mijclive. I'ulie Siipporlin^; ()lijecli\e Cell. Dr.iw Tiilii- of Micros.. ipe Olijclive. I'ins on Draw Tulie. Slots in Supportins; I'ulie. ( apsl.iii Kinn lor Cenleriiit; ()lijecti\e. Capstan Nuts (Iperalinn Dr.iw Tiilie. Plaster of I'.iris Kille. I.ir. Spring C.ileh. Rinn. Diaplir.ii;m Sup|Mirl. Srews Holding l)i,iphrai;m Siipporl. Cipsian Nrews f.ir Ceiit.Tini; Di.i- phi.i^ni. Si rew s. Micrometer C.irriane. Movable Ihr.'.ul. Mi.T.imelir Screw. Spriniis. Di.iphr.ii;!!' Kini;. Drum. C.ear. Milled Head. In.lex M.irks. kecordcr. Index Mark. Screw. Cover Screws. Srews. Screws. Five I'.ir.illel Spi.ler riueads. Transverse Thread. Kociissinn Nut. Kocii-sini; Nut. Draw Tiil)i'. Supporting Tube. Rheost.ii Kesisl.inci- Win-. Rubber I .ire. Hrass Casini;. C.mt.ict Sprini;. kiiiK ( l.imp. Neitr.il Wire, ('oni.icts. Switch Rin«. Switch. Instrument Clamp. Latitude .\ri. Cap^l.in ( .illim.ilion Screws. 9230.S— 5 65 INDKX (II- NrMI!i;Ki:i) parts -(■..ii((h'/.i/. im Nrow- lloMiiiy Mirrcmuli r I'.vr pii re in r.'l.-. -,'•■. 11 IihUa ■'! \!m r..-,,.|.. l>rum. 1-' ( li|». l.> ( laini'in.; '^i n ■'•~ 11 L,mI!i.i„ Nr. ■■ :-. 15 II. .ri/-. .!.'■' < i.iuip. Ill lli.ri/ii.n.n 1 !'.:;■.!:' ■>. n a . i: ln,ll.-u,- H.M.I. is ''Iniitrr Ih .1.1. I'l \, ni. ,i.! I ir. !<■. J(l Ki.i.l.r. J I \ iili. .il r.ni^.ni ^i re « 12 ( Kiriipiim \in. \l.y ( .ip-t.Mi N rcw . I jj rr.iirrli.in .m I ppcr I'l.ilc. 1 i5 ( .i|i-l.ii\ >i rrw . l_'(i I T.iii-\i r-i A\i-. I l.iiiiii r.iii.ci 111 ^iTfW . 127 Amuil.ir K.i-i' '>! I'.Vf I'i' . r \li. n.ni- >rriw- il.ililiii.; ( . illim.il i. m l.iiiiMr ( iiiiii. -. l,!(l r.i-.iriiii; ..1 lrl(-ii>i>i Mil r.>im irr. l.il Min.Mni I. 1- l>."l\ . \M K.i.ii inu \\,i-li. r. 66