The Bakerian Lecture. On the best kind of steel and form for a compass needle

On the return of the first expedition from the discovery of a North-west Passage, the compasses were reported to have become nearly useless, from the diminution of the directive force consequent upon the near approach to the magnetic pole. The azimuth compasses on that occasion being of the author’s invention, he was anxious that the second expedition should be furnished with instruments combining the utmost power and sensibility; and was consequently led to the researches, the mode of conducting which, with their results, form the subject of this lecture. In respect to the best material for the construction of compass needles, Captain Kater found that clock springs made of sheer steel were capable of receiving the greatest magnetic force, and that in forming the needle it should be exposed as little as possible to heat, by which its capability of receiving magnetism is diminished.