I'! ^* 



MAGNETISM. 



As for number 21, it pofleOed the fimple properties of Toft 

 iron : for the (borteft cylinder which could be taken from a 

 rod of this fize by means of a cutting file, dropped from the 

 end of the horizontal bar as foon as the magnet was with- 

 drawn. 

 Remuks on It is difficult to fay, which of the 11 wires mentioned 



^^?- 5<^' above, had the magnetic virtue in the mod perfediion, be- 



caufe each piece differed in diameter from the reft ; befides 

 which, it is very well known, that a mafs of iron, of a 

 weight and figure determinable by experiment only, is at- 

 tradied by any particular noagnet, more powerfully than any- 

 other mafs of the fame metal. But the preceding trials have 

 difcovered one circum fiance apparently of fome importance, 

 for they fliew that wire is converted into a conditional magnet 

 by its paflage through the 22 wordle, or wire drawers in- 

 ftrument ; and that the 23d operation brings this quality in 

 it to perfeflion as far as we can judge from experiment, 



I here only fpeak of wire drawn in Kendal, for I have been 

 told, that the fame article manufactured in fome parts of 

 Yorkfliire, has a much greater propenfity to become magneti- 

 cal. This information was communicated to me by Mr. 

 Morrice, a very intelligent fuperintendant of a manufaflure 

 of cards in this town ; who moreover obferved, that wire of 

 this defcription acquires a degree of raagnetifm under the 

 fiiears, which induced him, when employed in working if, 

 to fubfiilule a brafs gauge for the common inftrument made 

 of iron. 

 Conjectures re- The magnetic property which commences with number 22, 

 lative to the feems to be common to all the finer fizes, for I found it in 

 the fmalleft wire I could procure, and which apparently did 

 not exceed a ftrong human hair in thicknefs. 



The foregoing experiments, befides proving that flender 

 wires acquire a magnetifm which is permanent as long as 

 they remain in contaft with iron, alfo affords an exception to 

 a fecond general maxim of the fcience, which afTerts, that the 

 permanency of communicated magnetifm depends on the 

 hardnefs of the ferruginous body that receives it. This does 

 not appear to be the cafe in experiment 2, in which wire of 

 No. 32 did not lofe the faculty of being convertible into a 

 conditional magnet after undergoing a red heat, a procefs 

 that is well known to render wire very foft. 1 even repeated 

 the expeiiment with the fame refult on all fizes betwixt 22 



and 



caufc. 



