VOL. XLVir.] PHILOSOPHICAL TRANSACTIONS. J 33 



and place them together, so as to make a double bar in thickness, the north 

 pole ol" one even with the south pole of the other ; and the remaining 2 being 

 put to these, one on each side, so as to have 2 north and 2 south poles together, 

 separate tlie north from the south poles at one end by a large pin, and place 

 them perpendicularly with that end downward, on the middle of one of the 

 parallel bars, the 2 north poles towards its south, and the 2 south poles to- 

 wards its north end : slide them backward and forward 3 or 4 times the whole 

 length of the bar, and removing them from the middle of this, place them on 

 the middle of the. other bar as before directed, and go over that in the same man- 

 ner ; then turn both the bars the other side upward, and repeat the former ope- 

 ration : this being done, take the 2 from between the pieces of iron, and placing 

 the 2 outermost of the touching bars in their stead, let the other 2 be the outer 

 most of the 4 to touch these with : and this process being repeated till each pair 

 of bars have been touched 3 or 4 times over, which will give them a considerable 

 magnetic power, put the half dozen together after the manner of the 4 (fig. 4,) 

 and touch with them 2 pair of the hard bars, placed between their irons at the 

 distance of about half an inch from each other : then lay the soft bars aside ; 

 and with the 4 hard ones let the other 2 be impregnated (fig. 5) holding the 

 touching bars apart at the lower end near -^ of an inch, to which distance let 

 them be separated after they are set on the parallel bar, and brought together 

 again before they are taken off: this being observed, proceed according to the 

 method described above, till each pair has been touched 2 or 3 times over. But 

 as this vertical way of touching a bar will not give it quite so much of the mag- 

 netic virtue as it will receive, let each pair be now touched once or twice over, 

 in their parallel position between the irons (fig. 6) with 2 of the bars held hori- 

 zontally, or nearly so, by drawing at the same time the north of one from the 

 middle over the south end, and the south of the other from the middle over the 

 north end of a parallel bar ; then bringing them to the middle again without 

 touching the parallel bar, give 3 or 4 of these horizontal strokes to each side. 

 The horizontal touch, after the vertical, will make the bars as strong as they 

 can possibly be made : as appears by their not receiving any additional streno-th, ' 

 when the vertical touch is given by a greater number of bars, and the horizontal by 

 those of a superior magnetic power. This whole process may be gone through in 

 about half an hour, and each of the larger bars, if well hardened,* may be 



* The smith's manner of hardening steel, whom Mr. C. chiefly employed, and whose bars have 

 constantly proved better than any he could meet with beside, is as follows : having cut a sufficient 

 quantity of the leather of old shoes into very small pieces, he provides an iron pan, a little exceedino- 

 the length of a bar, wide enough to l.iy two side by side without touching each other or the pan, and 

 at least an inch deep. This pan he nearly half fills with the bits of leather, on which he lays the 

 two bars, having fastened to the end of each a small wire to take them out by : he then quite fills 



