26 



communication of magnetism to a steel plate or ring, which 

 he supposes others had failed to do. Dr. Patterson observed 

 that, on the contrary, nothing is better known in experimental 

 science than that magnetic polarity can be given to steel in any 

 form, and with as many poles as the operator pleases. In 

 illustration of this remark, he exhibited to the Society a steel 

 plate, prepared some years ago by Mr. Saxton, who was then 

 in London, according to an experiment first made by Chladni, 

 on which polar lines were traced, so as to mark on one side the 

 word ' magnet j and on the other the date '24th of February, 

 1836;' the position of the lines being made apparent by strew- 

 ing steel filings over the plate. 



2. Dr. Sherwood asserts that, if a steel ring, marked in two 

 opposite points, have magnetism communicated to it by passing 

 it over a magnet from one of those points to the other, in a way 

 which he describes, the magnetic poles will be found to reside, 

 not in the marked points which he styles the poles of the ring, 

 but in other points distant from them 23° 2S', thus exhibiting 

 a correspondence with the obliquity of the ecliptic. On this 

 fact he founds his theory of the magnetism of the earth. 

 Dr. Patterson mentioned that Mr. Saxton and himself had 

 carefully repeated this experiment, and had found, without 

 surprise, that the assertion of Dr. Sherwood was entirely 

 erroneous. When the magnetism was communicated in the 

 awkward manner used by Dr. Sherwood, the poles were not 

 indeed at the points of the first and last contact of the mag- 

 net; but the deviation was irregular, was different at the differ- 

 ent poles, and bore no relation to the obliquity of the ecliptic. 

 When the magnetism was communicated to the ring by care- 

 fully setting two opposite points on the poles of a horse-shoe 

 magnet, the magnetic poles of the ring coincided exactly with 

 those points. This fact was shown in an experiment made 

 before the society. 



3. As to the hypothetical deductions of Dr. Sherwood, " that 

 the magnetic poles of the earth are 23° 28 : from its poles, and 

 of course within the polar circles," "that the magnetic and 

 polar axes cross each other at the same angle of 23 p 28'/' 

 "that the magnetic and terrestrial meridians of every place 

 cross each other at angles dependent on the angles of the two 



