Show IS WORLDS WORLD'S TIME CE CENTER CENTERI I I Elaborate EI System el by Which h. h j I Are M at Made de-at de Gr nW f ri ng g- g tk I l land a and d M Made PU I r J e. e I The C astronomical ca in l Ain Instruments Instruments In In- on oil the roof of rh logical building at G GIt en ll lc-h. lc II ng I Ph r wake the scene nn an i ut l' l t Ing one Olle o i Here In this b bulling Is the time i center iff r the world lime ime is Es usually f Jay Jy Val watching ching ti t stars tr The stars are used for thIs e f they because they are arc many and bUn iju is but one Star life t taken ut at variouS Un times es throughout the tho day and und nt night ht hUe the sun SUI ui h be IH used I but once n i day I z i This Is how IS-how how v observations aie le made wade f at nt Gl n nr r h- h About two vo minutes lh tes t. t before tl ui n appointed poInted time ill the operator takes his place at the yc piece lC of the lie J telescope A As le Ue looks hi Ill my sees stes n a number number num nurn ber ber of vertical Iines These aie atu spider r threads placed place in tIll f fo IU riia us of the e eye v 11 Presently a u bright point of or suF su- su F vcr ver er light comes moving quickly on- on Wai tL- tL The rhe watchers watcher's hau hand band now seeks the side of the telescope until his Ils finer fingel finger fin fin- gel ger er finds a little button over over which It rests rca ready y to strike stride e On comes the theE E star without haste without rest until un Ull- e. e til It It r reaches aches one one of tb the the gleaming threads Tap I The finger falls fails sharply sharp sharp- ly Iy on the button hutton II In three or f fur four seconds sec see the star has hns readied reached another thread Tap Again Aguin the hc button Is 1 struck nn and so on until the Hie ten t threads breads have been passed and the lie transit Is over Now let us ns consider what the finger taps have hs done one Each tap completed r for or an instant an electric current and recorded a the chronometer This is a metal cylinder covered with leI Imd tumid by by y a carefully regulated clock dock once In er e every two minutes winA win min utes A similar l mark is made once in every cry two seconds b by a current sent by ly 1 means weans of the standard t sIdereal clock of of u the ob If then one of the clock dots duts and one and one of the observers observer's observers observer's ers er's dots come side b by side It Is 13 known at fil what precise second the I tar star was on one of or the wires as LS the i spider threads are called callerI If It the tho observers observer's ob ob- ob- ob se servers server's dot comes between two clock I do dots It Is easy by measuring its distance dis dis- dis tance tane from om them with v dIng scale t to tell the Instant the tue was on the the- wire I C to the tel tenth th part purt n rt of of f n ii s second I. I f Ol f'S f J J t J 11 1 1 1 t f. f 1 r- r f. f 11 f i fi rr Ai v. v 4 4 It If y a S l Tr j J L lfF 10 f f rk J ii 7 J 1 I t j j jt Ii t g l' l rf r. r z 1 f J- J Greenwich Ob Observatory 4 Sl e e the transit was IlS taken jaken over tEnt ten t wires and the distance of each wire r J from the i of t th lEN fi field lJ of vi view t Is Is known pr practically te ten separate observations ob ob- b. b have been made thade and th thI the I IL u ar average rage of or these gives t the le time of transit f f r I At the observatory there is a gi gu 1 a clock cloel si sidereal clock clod wb r 21 24 hours bours n lh the precise l tn iii l th the earth enith lo it j. j on oc r res on In r it its its- axIs 01 ii i the v ri g s sta u 1 a aln app appear al ai on on lf affixed meri meri- f hence nce since the e exact act time Is l kno o when star tar ought to b be o on r. r the tho meridian this cJ clock ock crin can bo be readily checked leCk d by th the observations o of star transits a aBy n Bj By this o in method tl o the We error of tilt the do dock Clock l Is determined twice a adny day shortly before 10 o'clock in the morning aJl and shortly before otio o'clock In the afternoon These two t ues Rl aie nrc cho- cho tm n because at 10 and md 1 o'clock L signals ire are tent tent- nt t to all the thc groat grat provin- provin i iclal cia I centers Also at 01 O. O the time at Greenwich and at at Deal are are dropped so that lint the captains of ships hIps within sight of the dropping dropping- mst mast ma may set fet their chi Is time found and oud regulated A. A nt at the great oh observatory V |