Page:Philosophical Transactions - Volume 050, part 1.djvu/379

 has increased from 2°¼ W. to 12°¾ W.; and in latitude 15° N. longitude 20° W. it has increased from 1° W. to 9° W.

But there is still a more extraordinary appearance in the Indian seas: for instance, under the equator.

Longitude from London

Variation in

1700. 1756.

Degrees. Degrees. Degrees.

40 E 16¾ W 16¾ W

45 E 17¾ W 14½ W

50 E 17½ W 14¾ W

55 E 16½ W 8¾ W

60 E 15¼ W 6 W

65 E 13½ W 4½ W

70 E 11½ W 3¼ W

Longitude from London

Variation in

1700. 1756.

Degrees. Degrees. Degrees.

75 E 9¾ W 1 W

80 E 7¾ W 0¼ E

85 E 5½ W 1¼ E

90 E 4¼ W 1 E

95 E 3¼ W 0¼ W

100 E 2½ W 1 W

Where the west variation in the longitude 40° E. is the same in both the above years; and in 1700 the west variation seemed to be regularly decreasing from longitude 50° E. to the longitude 100° E.; but in 1756 we find the west variation decreasing so fast, that we have east variation in the longitude 80°, 85°, and 90° E; and yet, in the longitude 95° and 100° E. we have west variation again.

Such are the irregularities, that experience hath shewn us, in the variation of the magnetic needle; which appear so considerable, that we cannot think it wholly under the direction of one general and uniform law; but rather conclude, with the learned and judicious Dr. Gowen Knight, Fellow of this Society, in the 87th prop, of his treatise upon attraction and repulsion, That it is influenced by various and different magnetic