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X. The Bakerian Lecture . On the best kind of steel and form for 
a compass needle. By Capt. Henry Kater, F. R. S. 
Read February 1, 1821. 
On the return of the first expedition which sailed for the 
discovery of a north-west passage, it appeared that from the 
near approach to the magnetic pole, and the consequent di- 
minution of the directive force, the compasses on board had 
become nearly useless. Some of the azimuth compasses 
employed on that occasion were of my own invention ; I was 
therefore anxious that the next expedition, which was about to 
„ sail under the command of Lieutenant Parry, and which has 
happily returned with so much honour to those engaged in it, 
should be furnished with instruments of this description, com- 
bining as much power and sensibility as possible. 
It was with this intention alone that I commenced the ex- 
periments which form the subject of the present paper ; but 
which I should not have deemed sufficiently important to be 
made public, had I not lately, on resuming the enquiry, been 
led to some results which appeared of sufficient interest, as 
well as practical utility, to induce me to lay them before the 
Royal Society. 
My immediate object was to ascertain the kind of steel, and 
form of needle best calculated to receive the greatest directive 
energy with the least weight. 
Two needles were prepared of that kind of steel which is 
called blister steel, and two of spur steel, the weight of each 
