An elementary book on electricity and magnetism and their applications . William Thomson, Lord Kelvin (1824-1907). A British physicist and electrical engineer ; horn in Belfast, Ireland ; for morethan fifty years professor of physics in Glasgow University, Scotland; in-vented the mirror galvanometer used in cable signaling; developed an im-proved form of mariners compass. His work in thermodynamics is of thegreatest value. He was one of the first to appreciate the principle of Con-servation of Energy. NATURE AND PROPERTIES OF MAGNETISM 133 rate magnetic survey of the important portions of the
An elementary book on electricity and magnetism and their applications . William Thomson, Lord Kelvin (1824-1907). A British physicist and electrical engineer ; horn in Belfast, Ireland ; for morethan fifty years professor of physics in Glasgow University, Scotland; in-vented the mirror galvanometer used in cable signaling; developed an im-proved form of mariners compass. His work in thermodynamics is of thegreatest value. He was one of the first to appreciate the principle of Con-servation of Energy. NATURE AND PROPERTIES OF MAGNETISM 133 rate magnetic survey of the important portions of the earthssurface. 100. A ships compass. The form of ships compass whichis now quite generally used was introduced by Lord Kelvin(Plate VII, opposite p. 133). It has a ten-inch card consisting ofa thin sheet of aluminum or paper on which a scale is pasted, ordrawn, and varnished. The middle portion is cut out for the sake. Fig. 81. — Kelvins compass card. of lightness. In this middle area six magnets are slung on to radialthreads, as shown in figure 81. In this way the oscillations of themagnets are small and are quickly damped out. In some formsthe card is floated on liquid, which takes most of the weightoff the needle point and also serves to stop the it is seen that in the ships compass the iV-point on thescale is always pointing approximately toward the north. Tosteer in any particular course, as northeast, the ships helmis turned until the northeast on the movable scale is opposite a 134 ELECTRICITY AND MAGNETISM fixed vertical black line, which is drawn on the inside of the course, it must always be remembered that the compass needletends to point in the direction of the magnetic meridian and this is seldom exactly thesame as the geographicalmeridian. It will alsobe noticed that the com-pass bowl (Fig. 82) issupported on gimbalbearings, so that, no mat-ter how much the sh
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmagnetism, bookyear19
