( 99 ) 
When the two firfi Needles were made narrower, care 
was taken that the Files made ufe of for filing the 
North Ends, touched not the South Ends ; and after 
they were made lighter, I tried them both, before they 
were frefli touched upon the Stone, and found no fen- 
fible Difference in their Direction. The reafon of ma- 
king the two firfi Needles fo heavy, was to try whe- 
ther they would return more conflantly to the lame 
Situation than lighter ones. But notwithflanding each 
of them would lettle verv exa&lv in the fame Place, 
for a great Number of Trials made immediately one 
after another, yet I found them at different Times to 
differ confiderably from their former Directions. 
This occafioned my making them narrower, fearing 
their Breadth had been fome way concerned in this Ir- 
regularity. But after the Alteration, I found the fame 
thing happened, though I could find nothing of it to 
proceed from any Fri&ion upon the Point. This 
made me prefer the lighter Needles, as lefs apt to in- 
juie the Point they moved upon, and as ex a Cl in re- 
turning to the fame Situation. After many Trials, I 
found all the Needles I made ufe of, would not only 
vary in their DireClion upon different Days, but fre- 
quently at different times of the fame Day ; and this 
Difference would fomeiimes amount to upwards of 
half a Degree in the fame Day, fometimes in a few 
Hours. And this Alteration I obferved, whether the 
Needles were drawn afide immediately before the Ob- 
fervation, or fuffered to remain undiflurbed. For I 
have left the Box Handing for feveral Days together, 
without ever diflurbing the Needle, only have taken 
notice what it pointed at, and the Time of the Day, 
and I could fometimes perceive in a few Minutes a ve- 
ry ftnfible Alteration. But whether it flood near its 
greatefl 
