r >87 1 
be loft by ftriking as many Blows with it againft the 
Ground with the other End : Then ftrike another 
Blow or two, and the End which attrafled the North 
End of the Needle will now attraft the South End, 
and fo vice verfa , the Pofition being ftill hori- 
zontal. 
If the Blow be' given againft the Ceiling, or any 
horizontal Body, with the upper End of the Bar, the 
fame Virtue will be communicated as before. 
This will likewife happen, if the upper or lower 
End of the Bar be ftruck with an Hammer or Mal- 
let $ whether the Blow be given end-wife or at Right 
Angles to the Bar: Nay, though it fhould be given 
in the Middle of the Bar $ the Pofition of the Bar 
at receiving the Blow being all that is requifite ; for 
if you give the Bar only a Jerk or Shake in that ver- 
tical Pofition, it will receive the Virtue, as if there 
were in the Iron feveral Threads or Beards fix'd at 
one End, as Monjieur "Du Fay fuppofes, which the 
Blow or Shake laid" all one way, and which were 
plac'd the other way by inverting the Bar, and then 
giving it a Shake or Blow. 
N. B. When the Bar is plac’d horizontally, a Blow 
in the Middle deftroys its Virtue. 
XL The 
