magnetical properties in steel and iron by percussion. 251 
hammered in succession, and in a few minutes they had all 
acquired considerable lifting powers. Two of the smaller 
bars, connected by two short pieces of soft iron in the form 
of a parallelogram, were now rubbed with the other four 
bars in the manner of Canton. These were then changed 
for two others: and these again for the last two. After 
treating each pair of bars in this way for a number of times, 
and changing them whenever the manipulations had been 
continued for about a minute, the whole of the bars were at 
length found to be magnetised to saturation ; each pair rea- 
dily lifting above eight ounces ! 
In accomplishing this object, I took particular care that no 
magnetic substance was used in the process. All the bars 
were freed of magnetism before the experiment, so that none 
of them, not even the largest, produced a deviation of five 
degrees on the compass at three inches distance. The ham- 
mers were also carefully examined. Any bars which had 
been strongly magnetised, and had had their magnetisms 
destroyed or neutralised (either by hammering, heating, or 
by the simultaneous contact of the two poles of another mag- 
net placed transversely,) I always found had a much greater 
facility for receiving polarity in the same direction as before, 
than the contrary. Hence it generally happened, that one 
blow with the original north end downv/ard, produced as 
much effect as two or three blows did with the original south 
end downward. I also observed that the polarity of pokers, 
generally supposed to be permanent and considerable in in- 
tensity, was rather transient and weak : for in no instance 
did I meet with a poker, the magnetism of which I could not 
