MAGNETISM. 35 



It is evident that Mr. Barlow thinks that iron bodies, not per- 

 manently magnetical, do not act as magnets on the compasses ; 

 he mentions an experiment made with some fine iron filings 

 strewed on the surface of water, (at the suggestion of a philoso- 

 pher of eminence), which were not acted upon by the lower part 

 of an iron sphere, and he rests the fate of his theory on the issue 

 of this experiment. (See article 190, page 182, of Mr. Barlow*s 

 work.) 



A hundred years ago, a Mr. Servington Savery, presented a 

 paper to the Royal Society, detailing the result of his experi- 

 ments and observations on magnetism : the following being an 

 abstract of some of his conclusions, 1st., that the poles of magnets 

 attract most vigorously, and that the middle does not attract at 

 all. 2nd, that he could not discover any difference between the 

 force of attraction and that of repulsion in the same pole of any 

 loadstone or magnet, unless when a small one approached so near 

 to a large one as to have its polarity diminished. 3rd, that these 

 properties convinced him, that there is no such thing in nature as 

 magnetic attraction without polarity, which is made up of attrac- 

 tion and repulsion. 4th, that of a soft iron bar, void of fixed 

 polarity, as soon as it is in an erect position, the higher part, from 

 the middle upwards, becomes a south pole in north magnetic 

 latitude, and the lower part from the middle downwards, be- 

 comes a north pole in north magnetic latitude, and a south pole 

 in south magnetic latitude, but that, as soon as the bar is in- 

 verted, the polarity is inverted in it, the end before being a 

 north, is now a south pole : he states, that the case is the same 

 when the iron bar is suspended, or placed horizontally, in the 

 direction of the magnetic needle ; and he thinks that this mag- 

 netic virtue is communicated to the iron, " by the earth's central 

 magnet." 



The above abstract fr.am Mr. Savery 's paper, is sufficient to 

 show, that he differs in opinion from Mr. Barlow ; Mr. Barlow 

 denying the polarity of soft iron, and Mr. Savery affirming, "that 

 there is no such thing in nature as magnetic attraction without 

 polarity." 



In the course of my professional services, being charged witii 

 the navigation of ships, and having served in both hemispheres, it 

 became necessary that I should make myself acquainted with 

 magnetism, so far as it appli^d-k) masses of iron likely to affect 

 the steering compasses, and, in order to form a judgment of the 

 action of masses of iron on the magnetic needle, I was in the 



