LOCAL ATTRACTION IN SHIPS.

New Zealander, Volume 8, Issue 681, 23 October 1852, Page 2

LOCAL ATTRACTION IN SHIPS.

fFiom the " Nautical Magazine.",) It appears that this subject has at lengtli forced itself into notice. Does or does not the compass misbehave itself from the above cause in southern latitudes'? Some answer yes, and others no. Where the dangerous plan of applying correcting powers to the compass is adopted we apprehend that it does generally, and it is shown so in the following letter. "Topsbam, Devon, April Bth, 1852. t( Sir, — I received the inclosed paper a few days since from my son Alfred Mering Sainthill, who commands the Keera, and as the information may be useful to home of the steam ships about to proceed to Australia, I lorward it to you to publish it if you think proper. ] The Keera's compasses were adjusted in Newcastle previous to her departure. "I am, &c, I " Alfred Saimiiill, Lieut. R.N. Remarks on the Compasses of the Iron Steam Boat Keera from Newcastle to Sydney. — Correct as f aras the equator, first found wrong in the south-east tiade, Octobei 3rd, 1851, lat. 27° S., long. 23 Q 52' W., ship's head by compass S W.,true S.W.by S. On getting to the southward of the south-east trade, the deviaiiou increased as we got to the eastward. In lat. 41°, 51' S., long. 35° 45' E., the course by observation was N. 89° E. ; course by binnacle compass E. b. N. ; course by cabin compass, S.E.^E., deviation of binnacle compass increasing. November 28th, lat. 40°, long. 82° 40' E., steered north-east to make an east course. On Thursday, December 3rd, Int. 42°, long. 100° E., in a heavy gale, hove to, the compass frequently changed ends, sometimes continuing reversed two or four hours, and then vibrating a long tiire, in fact useless. They continued so until the 6th, when I reversed the poles of the antagonist magnets, and removed them about two feet iuither from the compass, after which we made good courses with the ship's head east, but found the compass sometimes one point wrong, ship's head north on the coast." # No correcting powers are applied in H. M. ships, nor should they be for many reasons. The amount of error is always found and allowed ior. Further attention is called to the subject by the following Admiralty oider : — " Admiralty, May 12th, 1852. " My Lords desire to call the attention of the captains and officets of H. M. ships and vessels, to the necessity of constantly watching the deviation of the ships' comr>,is6es, caused by the atti action of the ii on in ships, especially in steam vessels, and more particularly in those constructed of non; experience having shown that large eriors are caused thereby, which not only vary in degree when approaching the magnetic equator, but in many instances, when passing to the southward of it, require the correction for eiror to be applied in a contiary direction to that previously ascertained With a view of taking such further precautions as appear to be neceßbary to guard against the dangers arising from the above cause, my Lords are pleased to direct as follows : — "Ist. All ships and vessels are to be swung once in each year, for the purpose of ascertaining the errors of the compass of the ship, also immediately on their armal on a foreign bta'ion ; or if there has been any grent change in the ship's position since the errors were last observed. "2nd. Azimuth nnd amplitude obseivations are also to be t»ken at sea, for the same purpose, as pointed out in the practical rules supplied to 11. M. ships, for the guidance of officers. " 3ul. Whenever ships are swung, or observations are taken at sea, a notation of the circumstance, nnd of the amount of error, is to be inserted in the ship's log, and remark books, and a yearly return of the local attraction of the ship is to be transmitted to this office ■with thequaiteily returns ending December 31st, in tli c form at piespnt in uso. "4tb. It is always to be stated in the returns if the compasses have corrected by magnets.

•' Jiti. The attention of officers is partitululy called to cncular No. 9, dated November 20th, 1846, with rehToiim to the removal of iron from the vicinity of the tonijutsses."