Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity (1854)
Davis, Daniel · Boston : Palmer and Hall · leaf 153
e truebearing of the sun at the time, is then calculated.Suppose it equal to 85° 30. The difference betweenthe magnetic bearing and the true bearing, repre-sented by the angle M A N, is the variation of theneedle, and equals 9° 30.*= 217. Fig. 84 represents an instrument intendedto illustrate the… … through the coil of wire about the equatorial region,small magnetic needles, placed in different situations,arrange themselves as they would in similar terres-trial latitudes. By comparing this figure with Fig. * The variation at Boston, in May, 1847, was 9 deg. 30 rain.west. The dip, at the same…
