I'ASS. THE MARINER'S. 



COMPASS, THK MAKIN K1CS. 



o( adjusting it north and south, if the centre of the card be 

 nude the pivot of a magnetic needle. In the mariner*! oompus, how- 

 erer. it U usual to affix the neaxlle to the card, pointing towards iU 

 north and couth point, to that the card travel* with the needle ; and if 

 a pointer (fixed with nvpect to the ship) mark out the point on the 

 edge of the cant which lie* in the line drawn through the pivot panM 

 to the plane which symmetrically bisecU the ahip, the bearing of the 

 hip's head w shown by the part of the card to which the pointer 

 direct* for the time being. Instead, however, of a pointer being used 

 on board ship, it is usual for a mark to be drawn upou the inner 

 surface of the oompaas-bowl. a line between which and the centre of 

 the compass being always parallel to the ship's keel. To ensure the 

 horuontality of the compass-card, the cylindrical box or bowl in which 

 it is enclosed, is supported in a hoop at opposite point*, by pins pro- 

 toting from it, so as to allow the box to revolve inside the hoop. This 

 hoop is supported in the same manner on pivots, the line of which is at 

 right angles to the first pivot* ; so that between the rotation of the 

 compass-box in the hoop, and the hoop itself, the former can always 

 find its position of equilibrium, which U the horizontal position. The 

 nudl oscillations of the apparatus are immediately destroyed by the 

 friction. The apparatus is then said to be supported on gimbleg, or 



, 



By whom the suspension now generally used was invented, is alto- 

 gether unknown from any document or other evidence. The suspension 

 of the whole machine itself on two circles, whose suspending diameters 

 are at right angles to each other, is, however, on all hands admitted to 

 have been English, though we are still ignorant both of the person who 

 invented it or the period of the invention. It appears to be traditional 

 evidence on which the opinion rests; but a tradition in which rival 

 nations agree, bearing on an invention which would be honourable to 

 any one to have a power to claim, can hardly be supposed an erroneous 

 one. Voltaire, in his essay on ' Universal History,' seems to confirm 

 the English claim, when he admits that " the first who certainly made 

 use of the compass were the English, in the reign of Edward III." 1 1 

 peaks of a Carmelite friar of Oxford named Linna, an able astronomer 

 of those days, having sailed as far as Iceland, when he drew chart* of 

 the North Seas, which were afterwards made use of in the reign of 

 Henry VI. But Voltaire should have applied his assertion to an 

 improved form of it, rather than to the circumstance of its use for the 

 first time. Still, even in England, in the time of Queen Elizabeth, the 

 construction was very rude in its execution. 



The mechanism of the compass is a subject affecting so largely the 

 commercial interests of Great Britain, that not only does the safe 

 transit of the goods of the merchant depend on it* proper adaptation 

 to the principles on which magnetism can be available to the sailor, but 

 much of the safety of ships of war, in particular, will be involved in 

 the accuracy of working shown by these instruments. Our unnautical 

 readers will easily understand the importance of a correct manufacture 

 of the compass when the following case is assumed in illustration : Let 

 two ships of war, of equal size, shape, and fittings, and commanded 

 respectively by pilots of equal skill, attempt, in hazy weather, to enter 

 the Thames or some other estuary difficult of approach. Let their 

 compasses be from the same maker and alike, and of ordinary con- 

 struction, as now used in H.M. navy. It is quite possible that one 

 ship may reach her port in safety, while the other may Miller total 

 wreck ; for the secret of the safety or loss of the ships may even have 

 depended on the following simple circumstance : In the one case, the 

 wary old quarter-master at the " con binnacle " shall have attached a 

 piece of packthread to the compass-rim, by lightly jerking which occa- 

 sionally the compass-card will have been kept more "alive" on its 

 needle point, or have moved more freely on its pin ; while the quarter- 

 master in the other ship may have thought such precaution uncalled 

 for, and the sluggishness of the compaas have caused an erroneous 

 impression as to her courses. Some remarks, therefore, as to form and 

 manufacture are called for, having for their object the development 

 of a compass system calculated to avert not only existing inconve- 

 nience*, but those calamities which the introduction of iron into ship- 

 building in the merchant service, and the increased armament with 

 heavy ordnance (and especially the adoption of Armstrong's steel gun) 

 into her Majesty's service afloat, would, if unheeded, entail upon the 

 navies of the maritime kingdoms of the world. 



So much has been written and said upon the compass of late years, 

 so many of our ablest philosophers have devoted their attention to the 

 improvement of the mariner's compass, that, seeing the results of their 

 labours in the complexity and variety of form which have still further 

 complicated the question in the eyes of the unscientific, it will )>< .' 

 to review slightly the past, taking, however, the present condition ! 

 the compass as the best and most profitable subject for our consideration. 

 A alight glance at the history of the compass will assist us in our con- 

 clusions, inasmuch as the experience of centuries will have its bearing 

 upon and considerably influence them. 



The most simple and primitive fonu of the compass appear* to have 

 been either the magnetised needle thrust transversely through a corn- 

 stalk, and left floating in a screened basin of water [COMPASS, HISTORY 

 OF THE], a* used on the Syrian shore ; or the small Chinese needle, 

 resting, just below iU centre of gravity, upon a needle-point fixed on a 

 wooden stand. The greatest amount of steadiness on the one part, and 

 activity of the needle on the other, seem to have been obtained, so far 



as regards mere form. (We, for the present, leave intensity out of the 

 question.) But it must be remembered, that Hteadinms might amount 

 to sluggishness, and activity might merge into inconvenient oscillation. 

 A modified form, therefore, one combining both qualifications, has, 

 through many centuries, been the navigator's daideratum. It is curious 

 to notice how varied have been the attempts to produce a good and 

 unobjectionable compass. Still more are wo astonished and bumbled 

 to see in the most recent (so-called) " improvement " the very principle 

 of the floating compasses, as described in 1242 by lUilak Kibdjaki I 



Scarcely any modification of form had occurred, certainly for the 

 three centuries previous to the time of Richard Norman of Limehouse, 

 in 1590. Norman appears to have introduced some change, in what, 

 however, one would imagine his only im/irorftartit to have been, the 

 adding of a counterpoise to the ancii>nt ( 'hinese form of needle, ren- 

 dering it, by means of a weight sliding on the needle or bar, suscep- 

 tible of adjustment in removing it from one part of the earth's surface 

 to another. [Dtp.] Probably few successful attempts had, till very 

 recently, been made to examine the magnetic conditions and changes to 

 which the needle was subject, or the advantages of one form of the 

 needle itself over another. The only improvements seem to have 

 been those which insured greater nicety of construction. Our country- 

 man Michell subsequently increased the efficacy of the needle by his 

 invention of what was called the double touch, which symmetrically 

 diffused the magnetic influence in the two arms of the needle ; and 

 early in the present century. Captain Kater directed his attention to 

 the imparting of the greatest amount of directive intensity by experi- 

 menting largely on the form and temper of the metal of the bar. 

 Several men of science, and among them Professors Barlow, Lloyd, 

 Arago, Faraday, Wheatstone, Airy, Ac., and also Messrs. Biot, Many, 

 Coulombe, Dr. Oowan Knight, Dr. Scoresby, Sir Wm. Snow Harris, and 

 others, from the delicacy, beauty, and success of their experiments, 

 created an interest in the matter never before felt; but these researches 

 were, with some exceptions, rather confined to the properties of the 

 bar or needle than to the precise form of compaas to be used on ship- 

 board. It is however proposed to limit our considerations in this 

 article rather to the mechanical form of compass than to abstract 

 principles, which will be referred to in their proper place under the 

 word M.uiXLTisM. 



While it is admitted by many (and among them by Sir Wm. Snow 

 Harris) that the sensibility and delicacy of the primitive tinall needle 

 of the Chinese are quite surprising, and while Michell and many others 

 approve of the rei-y light steel bars of the Chinese to be used as 

 compass-needles (because magnetic power increases in a less degree 

 than the friction arising from increase of weight), it is singular that 

 those now in use are quite of opposite construction. As many as, or 

 more than, four or five bars being now attached to the same card, and 

 resting on the same needle-point, their weight, as might be expected, 

 increasing friction to such a degree that even agate caps soon wear out 

 ami become useless. Mr. Stebbing, an eminent optician at Southamp- 

 ton, partially obviates the inconvenience of this by substituting the 

 ruby. Few individuals gave more attention to magnetism and to the 

 accuracy of form in the needle than the late Dr. Scoresby ; but it 

 appears that no improvement in shape resulted from his long 

 continued labours. Dr. Oowan Knight, the first appointed principal 

 librarian of the British Museum, a man of persevering research in science, 

 who wrote a century since, described the form of compass-needle used 

 in his day by the merchant sen-ice as formed of two steel plates bent 

 at their centres and meeting at their ends, and forming the two poles, 

 in thiii manner : 



Fig. 1. 



But he found that when the temper of the metal in each piece differed, 

 the directive intensity was not in the axial-line of the mass, nor did 

 polarity at all times exist precisely at the emit of the needle. At the 

 same period he describes the form of bar as used in H.M. navy to 

 have been as under : 



Fig. :. 



In this he detected a capability of ita having no less than six poles', 

 while the greatest available directive force can only exist when there 

 are two. His investigations of the question established the still 

 admitted fact, that the form of needle best adapted to the mariner's 

 compass wan the regular paralM<>|'ipci|. Insing a straight bar with its 

 narrow dimension placed vertically. Hi. Knight also found that the 

 mode of suspension adopted l>y the Chinese, namely, the suspension 

 of the needle at a point a little below its centre of gravity, was the 

 best, as conducive to sensibility. He moreover recommended the 

 use of such a needle mt/mut cmiml /,irf'irntiiiu. Dr. Knight's form of 

 needle was for a long time adopted in H.M. ships; and, as Sir Wm. 

 Snow Harris, with undoubted propriety, in his excellent ' Manual of 

 Rudimentary Magnetism,' suggests, " it in still worthy of serious 

 attention." Perhaps in no one branch of science has more valuable 



