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Local attraction in iron vessels
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. T h e use of heat is omitted, which would be prejudicial to the coating of zinc.
Local.qltraetion 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" t h e 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 o f which Mr. A i r f s 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. T h e 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 o f 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 o f 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.
4 t 2 Progress o f Practical 4" Theoretical Mechanics ~. Chemistry. Dr. Faraday stated that the Professor's plan had been tried with complc,te success on board the Ironsides~ in her voyage to South America, and also on board the Rainbow, on her recent trip to Antwerp, but it elm scarcely be expected that the complete success of this ingenious method of Protessot Airy's should be securely established without much longer experience. When we consider the very complicated character w h i c h a vessel, considc,red as a magnet, must under all circumstances present~ her extreme li~,bil. ity to change her magnetic condition by concussion, by alteration of trim, &c,, anti when we further take into account the effects consequent on change of temperature, ~md on the vessel's removal from station to station on the earth*s stlrfitce, ',','¢'~ tn~ly reascmably expect that the plan will still meet with many practical difficulties, ere it c:~n be pronounced perfectly successful. Much~ howe.vo.r, has bo.en effected, and we cannot but congratulate the pub. licon the introduction of a piauso haiq)ily conceivc,d~ and thus far so suc(:essfi~lly applied. "L'he compass is now no longer a u~eless instrument on hoard our iron vessels~ anti though much caution must still be exercised in its application, the ptincipaldi~ficul~.iesseem to he removed, and the conlmandersof our iron vessels, with proper skill and care,, m;~ynow per(otto tl~esevoyages, (the short ones at least) with confidence and comfbrt. .Dr. Faraday, in concluding his subject, suggested the propriety of some public person being appointed to superintend the ~qq~lication of'these "cotrectors" whenever they may be employed, since the principle, however good in itself, if" carelessly or ignorantly misapplied, might be productive of tile most disastrous consequences. Lono.s'taut.Mag.
Preparation of Pros,tan Blue. Bg Ll~wzs THoMPsox. In the usual mode of manufacturing Prussian blue,, the requisite carbon and nitrogen arc` obtained by decomposing animal matter in contact with potash, In this process~ the potash, being reduced to the metallic, state~ causes the formation of cyanogen, in consequence of" its affinity tbr that sub° stance. T h e quantity oft" nitrogen thrnished by a given weight of anftmal matte,r, is not large,, and, in the material employed by manulhcturers, seldom i~c,rhaps exceeds eigltt per cent.; and of this small quantity, at least one-half appears to be dissipated during the process, thus producin~ an enormous waste, of material, and at the same time increasing the size or'the appav~dns. Reflecting- on these circumstances, it occurred to me that the almospherc, might be made to supply~ in a very economical manner, the requisite nitro. gen~if'aliowed to act on a mixture of'carbon and potash, under ti/vourable circum.~tancc,s. T h e experiment proved, on trial, to be correct, anti in some measure exceeded my expectation; for the carbonaceous matter employed may be worked over ao-ain many times, and is even improved by each operation. I fbund it necess,wy to use iron, for areason which will be apparent in the explanation of this process; when iron is not ernployed~ a much higher temperature is required. To produce Prussian blue,, the ibl[owing method may be adopted, but experience alone can teach us the best proportiot~s; and in this, as in most of the arts, the caprice oft each manufacturer will probably lead to the adoption of various proportions of the ingredients used. Take of" potash~ or pearlash, 2 parts; Coke, cinders~ or coals~ f~ parts~ Iron turnings~ . 1 part.
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. T h e use of heat is omitted, which would be prejudicial to the coating of zinc.
Local.qltraetion 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" t h e 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 o f which Mr. A i r f s 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. T h e 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 o f 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 o f 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.
4 t 2 Progress o f Practical 4" Theoretical Mechanics ~. Chemistry. Dr. Faraday stated that the Professor's plan had been tried with complc,te success on board the Ironsides~ in her voyage to South America, and also on board the Rainbow, on her recent trip to Antwerp, but it elm scarcely be expected that the complete success of this ingenious method of Protessot Airy's should be securely established without much longer experience. When we consider the very complicated character w h i c h a vessel, considc,red as a magnet, must under all circumstances present~ her extreme li~,bil. ity to change her magnetic condition by concussion, by alteration of trim, &c,, anti when we further take into account the effects consequent on change of temperature, ~md on the vessel's removal from station to station on the earth*s stlrfitce, ',','¢'~ tn~ly reascmably expect that the plan will still meet with many practical difficulties, ere it c:~n be pronounced perfectly successful. Much~ howe.vo.r, has bo.en effected, and we cannot but congratulate the pub. licon the introduction of a piauso haiq)ily conceivc,d~ and thus far so suc(:essfi~lly applied. "L'he compass is now no longer a u~eless instrument on hoard our iron vessels~ anti though much caution must still be exercised in its application, the ptincipaldi~ficul~.iesseem to he removed, and the conlmandersof our iron vessels, with proper skill and care,, m;~ynow per(otto tl~esevoyages, (the short ones at least) with confidence and comfbrt. .Dr. Faraday, in concluding his subject, suggested the propriety of some public person being appointed to superintend the ~qq~lication of'these "cotrectors" whenever they may be employed, since the principle, however good in itself, if" carelessly or ignorantly misapplied, might be productive of tile most disastrous consequences. Lono.s'taut.Mag.
Preparation of Pros,tan Blue. Bg Ll~wzs THoMPsox. In the usual mode of manufacturing Prussian blue,, the requisite carbon and nitrogen arc` obtained by decomposing animal matter in contact with potash, In this process~ the potash, being reduced to the metallic, state~ causes the formation of cyanogen, in consequence of" its affinity tbr that sub° stance. T h e quantity oft" nitrogen thrnished by a given weight of anftmal matte,r, is not large,, and, in the material employed by manulhcturers, seldom i~c,rhaps exceeds eigltt per cent.; and of this small quantity, at least one-half appears to be dissipated during the process, thus producin~ an enormous waste, of material, and at the same time increasing the size or'the appav~dns. Reflecting- on these circumstances, it occurred to me that the almospherc, might be made to supply~ in a very economical manner, the requisite nitro. gen~if'aliowed to act on a mixture of'carbon and potash, under ti/vourable circum.~tancc,s. T h e experiment proved, on trial, to be correct, anti in some measure exceeded my expectation; for the carbonaceous matter employed may be worked over ao-ain many times, and is even improved by each operation. I fbund it necess,wy to use iron, for areason which will be apparent in the explanation of this process; when iron is not ernployed~ a much higher temperature is required. To produce Prussian blue,, the ibl[owing method may be adopted, but experience alone can teach us the best proportiot~s; and in this, as in most of the arts, the caprice oft each manufacturer will probably lead to the adoption of various proportions of the ingredients used. Take of" potash~ or pearlash, 2 parts; Coke, cinders~ or coals~ f~ parts~ Iron turnings~ . 1 part.