22 



iii.iiket to diametralt staaende Nulpunkter (Indexer), og 



Beslaget h skal være saaledes placeret, at naar Pejlskiven 

 nedsættes i dette med sine to Tapper i i, saa skal Linjen 

 mellem de to Nulstreger paa det faste Tverstykke g være 

 parallel med Skibets Diametralplan. Om en tyndere Fort- 

 sættelse af Tappen <i bevæger sig Diopterlinealen /,• med 

 sine Dioptere, og kan fæstes i en hvilkensomhelst Vinkel 

 med g ved Hjælp af Skruen /. 



Pejlingen foregik altsaa saaledes: En ( ibservatør pas- 

 sede Styringen og aflæste nøjagtig anlagt Kurs i Observa- 

 tionsojeblikket, en anden liavde Kronometret og Notice- 

 bogen. og en tredie stod ved Pejlskiven. Naar Skibet gik 

 støt, uden Giringer, og Kompasnaalen var i Ro, pejltes 

 Solen enten direkte eller, naar den var højere paa Hinden, 

 ved Hjælp af Skyggen af den vertikale Traad og Diameter- 

 stregen paa Linealen k. Naar disse var nøjagtig overet, 

 raabtes -Nu!" og Kronometrets Visende noteredes; deretter 

 opgaves anlagt Kurs, der ligeledes noteredes, og Ringen / 

 drejedes saaledes, at den samme Kursstreg kom overet med 

 Nulpunktet paa g. Inddelingen paa Ringen liavde da nøj- 

 agtig samme Stilling til Diametralplanet som Inddelingen 

 paa Kompasrosen liavde i det Øjeblik, da der blev raabt 

 "Xu". hvorpaa Pejlingen aflæstes paa Ringen i Aabningen 

 og ligeud for Diameterstregen paa Linealen Tc, som om den 

 var aflæst direkte paa Kompasrosen. Dersom Linealen Tc 

 under en forlig eller agterlig Pejling dækker Nulstregen, 

 benyttes de to Hjælpestreger, der er anbragte et vist Antal 

 Grader til Siden af den egentlige Nulstreg. 



Kronometrets Stand for sand Tid ombord bestemtes 

 enten efter dets Stand for Greenwich Tid og Skibets be- 

 regnede Længde eller, naar Dagstiden var gunstig, det er 

 Solen ikke for nær Meridianen, ved at tåge nogle Solhøjder 

 og deraf beregne Solens Timevinkel. 



Af den saaledes fundne Uhrkorrektion, den efter 

 Kronometret noterede Tid, Bredden og Solens Deklination 

 beregnedes Sidens Azimut. Forskjellen mellem Solens 

 sande Azimnt og Pejlingen af Solen gav de til de forskjel- 

 lige anlagte Kurser svarende Værdier for den devierende 

 Misvisning. Efter den ovenbeskrevne grafiske Methode be- 

 stemtes derpaa Middeltallet af de ækvidstante Værdier for 

 denne, hvilket antoges som den sande Misvisning. 



De følgende Tabeller indeholder Observationerne og 

 de deraf udledede Resultater, t = Klokkeslettet elter sand 

 Soltid, 8 Pejling af Solen. <i Solens Azimnt, 



screved a cross-piece, g. marked with two diametrically 

 opposite zero-points (indices), and the frame 7/ must be so 

 placed that. on inserting into it the dumb-card with its 

 two pivots i i, the line between the two zero-points on the 

 fixed cross-piece g will be parallel to themiddle fore and aft line 

 of the ship. On a thinner continuation of the pivot fl moves' 

 a cross-piece. k, with sight-vanes, which admits of being 

 fixed at any required angle with g by means of tbe screw /. 



The bearings were tåken accordingly as follows: — 

 One observer looked to the steering, and read off tbe exact 

 compass course at the moment of observation. another bad 

 charge of tbe chronometer and noted the time. and a tbird 

 observed the azimuth dumb-card. Now, when the ship kept 

 steady on her course without yawing, and with the com- 

 pass-needle at rest. the bearing of the sun was tåken either 

 direct or. for greater altitudes, by the shadow of the ver- 

 tical wire and the diameter-line on the cross-piece 1;. The 

 moment the shadow of the thread and the line were exactly 

 coincident, observer No. 3 called out to his colleague with 

 the chronometer. who noted and entered the time. after 

 which the directiou of the ship's head by the compass was 

 given, and entered in the note-book, the ring / being then 

 moved in such manner that the division corresponding to 

 the directiou of the ship's head by compass was made coin- 

 cident with the zero-point on the cross-piece g. Hence, 

 the division-lines on the ring had precisely the same posi- 

 tion relative to the midship line as the division-lines on the 

 compass-card at the moment observer No. 3 called out. and 

 the bearing was then read off through the open space in 

 the centrepiece li, the extremities of the diameter-line being 

 the index, exactly as though it had been read off direct 

 from the compass-card. Should the piece 1; when taking 

 a bearing in or near the directiou of the fore and aft 

 midship line cover the zero-point. recourse is in that case 

 had to the two lines drawn a eertain number of degrees 

 from the true zero-point. one on either side. 



The error of the chronometer on apparent time on 

 board was found either from its error on Greenwich time 

 and the ship"s computed longitude, or. at a favourable hour 

 of the day. i. e. with the sun not too near the meridian, 

 by taking a few solar altitudes and computing the hour- 

 angle of the sun. 



Krom the error of the chronometer thus determined. 

 the observed cbronometer-time. the latitude, and the suirs 

 declination, was computed the azimuth of the sun. The 

 difference between the true azimuth and the bearing of the 

 sun gave the values for deviating variation corresponding 

 to the different compass courses. By the diagramatic 

 method described above was found the mean of the equi- 

 distant valnes for the deviating variation. which we assumed 

 to be the true declination. 



ln the following Tables are set forth the ohservatious 

 and their computed results: f signifies apparent time: S, 

 bearing of sun: <i, azimuth of sun. 



