-104 PHILOSOPHICAL TRANSACTIONS. [aNNO i /SO. 



the norlli will constantly be a south pole, and that which is directed toward the 

 south, a north one ; and as soon as the ends of the bar are shifted, the polarity, 

 in respect of the bar., is shifted also, but not in respect of the earth, for which 

 reason this virtue is called transient, and is communicated by the earth's central 

 ujagnet in such liianner as other loadstones are said to do. 



That if a bar of iron or steel, not having the least degree of fixed virtues, be 

 placed in any position, except at or near to a right angle with the magnetical 

 line ; it will not only for the present receive a transient polarity, but if it re- 

 main so long, the said polarity will gradually become fixed or permanent, more 

 or less, according to the hardness or softness of the bar, and the time it has 

 remained in that position, and the angle its length makes with the magnetical 

 line, and the proportion of the length to its magnitude, the longest, casteris 

 paribus, usually receiving most virtue : and sometimes when all these advan- 

 tages concur, the polarity will be sensibly permanent in a little time, and not 

 require a very long time to be rendered pretty strong. 



That by placing the said bar afterwards in the same position, only with its 

 ends shifted, it will gradually lose its gained magnetism, and at length have its 

 polarity changed. 



That magnetism not only in touched iron and steel, but also in the loadstone 

 itself, is soon destroyed by fire. 



That though fire destroys fixed magnetism in steel or iron, yet if they are 

 set to cool in an erect position, or rather in the direction of the magnetical 

 line, they will gain more or less fixed virtue by the time they are cold ; but 

 especially steel heated to a seasoning height, and in that position cooled sud- 

 denly under water. 



That while a piece of iron of some magnitude is held at one pole of a load- 

 stone, it will increase the attraction of the other pole thereof, and enable it to 

 lift somewhat more. 



That if either pole of a magnet, large enough, touch one end of an oblong 

 piece of steel, not too large and long for the magnet easily to act on ; it will 

 transmit its own virtue to the other end of the steel which is farthest off, and 

 make it a pole of its own kind ; while the end that touches the stone has virtue 

 of the contrary pole : but the virtue usually is not so strong in the end which 

 is untouched, as in that which is. 



That a needle first equally poised, then touched and put to oscillate on its 

 pivots in the magnetical meridian, will in north latitude have its north end (i.e. 

 its south pole) depressed until it directs to the north-attracting point of the 

 central magnet ; where, after several oscillations, it will at last rest : and in 

 south latitude the south end will be depressed after the same manner. 



