Dr. knight's Magnetic a l Machine. 595 
via of each bar, though increafed in virtue, feemed not 
immediately to have acquired a communication with each 
other. However, it grew always more powerful after 
each of thefe operations; and it is more than probable, 
if a perfon could be found, who, with. equal patience 
and fkill, would, at proper diftances, repeat the fame 
procefs, that the prefent machine would acquire a degree 
of force fuperior to what the original ever poffeffed, for 
much depends upon time and a due pofition. If to thefe 
was added a frefh impregnation of each fingle bar, by the 
means hitherto made ufe of, you would probably poffefs a 
larger fund of magnetic power, than exifts in any artifi- 
cial magnet now in being. 
But if this cannot be obtained, if an able perfon cannot 
be prevailed upon to renew its vigour in this manner, it 
might poflibly afford the curious fome fatisfacftion, to 
know, whether, in its prefent flate, it lofes any force, or 
• acquires frefh virtue; to know, with fome degree of pre- 
cifion, how much weight it will now fufpend; and to 
obferve annually its variation. I need not fuggeft, that 
a trial of this nature demands no fmall attention. Even 
the motion of a carriage in the flreet, though at fuch a 
diftance as the fociety’s apartments, will make a confb 
derable variation. 
I do not know r , that the doctor left behind him any de- 
fcription of a compofition he had made to form artificial 
load-ftones. I have feen in his poffeffion, and many other of 
his friends have likewile feen, fuch a compofition ; which 
Vo l. LX VI. 4 I retained 
