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 148
ted horizontally. This formis represented in Fig. 6. The smallneedles in Fig. 81 are mounted inthe same manner. Sometimes avertical graduated circle is added, tomeasure the angle which the needlemakes with the horizon. In using aneedle whose motion is confined toa single plane, it must be so… … 132 DAVI S S MANUAL. rest in any direction in which it may be placed; ahigh degree of accuracy is, however, difficult ofattainment. 210. The dipping needle assumes, in various lati-tudes, the directions exhibited in the annexed dia-gram (Fig. 81), wherethe point of the arrowindicates the northpole,…
