Local attraction in iron vessels

1839 Journal of the Franklin Institute  
Local ./lttraetion in Iron Vesoel~. 411 taining on the surface a thin coating of zinc, and submitting the articles so prepared to the action of heat, till a colour approaching to that of gold is obtained. The object of the present invention, so far as it relates to coat.' ing copper and brass, is to obtain a good and sufficient coating of zinc on the surthces, in order to prevent or retard oxidation. The use of heat is omitted, which would be prejudicial to the coating of zinc. Local.qltraetion
more » ... in Iron Vessels On Friday evening, the 22d March, the Theatre of the Royal Institution was crowded to hear Dr. Faraday's lecture on the plan recently introduced by Protbssor Airy, the Astronomer Royal, tbr neutralizing" the effect of iron steam vessels on the compass. It is well known that this valuable and indispensable instrument therto been quite useless in these vessels~ unless removed to a most ine0nvenient height above the decks. This was noticed by Lieut., now Capt.,~r. Allen, in the Alburka, in Lander's last expedition to the Quorra; and as an-. other instance, it is related of the Rainbow, the iron steamer on board of which Mr. Airfs experiment was made, that her commander, at the close of a most anxious voyage from Liverpool, (where the vessel was built) was so much at a loss about his situation when off the Isle of Wight, that he was obliged to ask a fisherman where he was; on being told that he must steer E.S.E. (we think it was) to gain his port, he replied that he would give a good deal to know in what direction E.S.E. was, for being in an iron vessel, his compass was useless. It was on the arrival of this vessel at W'oolwich, that Professor Airy was employed to institute his inquiries respecting the best means of rendering the compass available in iron steamers. Dr. Faraday, in giving a general account of the method adopted by the Professor in his experiments, illustrated his subject by means of a large plate of sheet iron, which represented the vessel, above and towards one end of which, a horizontal magnetic needle was placed, similar in position to the binnacle compass. The sheet of iron was then made to traverse on a central pin placed immediately under the needle, by which arrangement the process of swinging the vessel was very simply exemplified. Mr. Airy, we are informed, having swung the vessel in the usual m~ti~i net, ascertaining for each point of the compass the magnetic variatibn~/a~d then by vibrating the needle under similar circumstances, ?h~ alsoobtai~ed the comparative magnetic intensity. By the application of mathematical reasoning to these data, he was enabled to estimate the general direction and amount of the disturbing toter, which was thus so michievously exerted in the needle, and to counteract which a remedy was now to be sought. From the extraordinary effects exhibited on the needle during these in. vestigations, the inference previously drawn by Capt. Johnson from his interesting experiments on board the Garryowen, in 1837, was confirmed~ namely, that the iron vessel did not act merely by inductive influence as a mass of self iron, but as aregular and permanent magnet~ exhibiting-the effects of determined polarity. Professor Airy, under these circumstances, has employed artificial mag. nets as "eorrectors," and so places them as to neutralize the effect of the vessel, and thus leave the needle subject to the earth's magnetic influence alone. It is obvious that the position of the "correctors" must he ascertained by separate experiments for each vessel.
doi:10.1016/s0016-0032(39)91726-6 fatcat:p5z3d42ta5dwrb74u4p2ny6t2e