Book II. chap. xxv. A strong, large, loadstone increases the power of another loadstone, and also the power of iron.
Book II. chap, xxxiv. Why a loadstone is of different power in its poles as well in the north as in the south regions (two experiments).
Book III. chap. xii. Iron becomes magnetized when red-hot and hammered in the magnetic meridian; also when the iron bars have, for a long time, lain fixed likewise in the north and south position (two experiments).
Book III. chap. xv. Two more experiments to show that the poles, equator, centre, are permanent and stable in the unbroken loadstone; when it is reduced in size and a part taken away, they vary and occupy their positions.
Book IV. chap. ii. Variation is due to inequality among the earth’s elevations.
Book V. chap. ii. Illustration of the direction and dip of a terrella representing the earth relative to the standard representation of the globe of the earth, at north latitude 50°.
Book V. chap. iii. Instrument for showing by the action of a loadstone, the degree of dip below the horizon in any latitude.
Book V. chap. vi. Of the ratio of dip to latitude and the cause thereof.
Book V. chap. xi. Of the formal magnetical act spherically effused.