S2 M r By water on the Mag netism of 'Brass-work . 
a miner’s dial. In repairing and adjusting this instrument, a 
regular attention was paid to those parts on which the correct 
action of the instrument depends; but after this had been done, 
the dial still remained imperfect, sometimes pointing correctly, 
while at other times its indications were quite erroneous. To 
counteract this irregularity, new agate-caps and needles were ap- 
plied, some of which were procured from one of the best makers 
in London, and the others were got up by an expert country 
workman ; yet the irregular action of the dial still continued, 
and the case seemed too difficult and perplexing to admit of a 
remedy. 
Under these disappointments, it occurred to me that the brass- 
work belonging to the instrument might be so far magnetic, as 
to produce the irregularity in question ; a conjecture which expe- 
riments proved to be true, for both the limb and ring were strong- 
ly magnetic. As a further proof that this was the source of the 
erroneous action, the above two defective parts were replaced 
by Mr Bate, and then the instrument became uniformly correct. 
Just after the dial had been put in good order, a person call- 
ed upon me, and, seeing the instrument, observed I had got 
“ a dial that was bewitched, for it had led many workmen 
astray ; and that he and five men had nearly been plunged into 
an old shaft by its incorrectness.” Upon further inquiry, he 
told me that it had been sent twice to the maker’s in London, 
three times to Derby, and twice to Nottingham, to be put in 
good condition ; but all of them returned it imperfect. Had 
these facts been stated to me when I received the instrument, 
most probably I should have suspected the character of the 
brass, without such a waste of labour, though nothing of the 
kind had occurred to me before. 
The accompanying limb or plate you will find strongly mag- 
netic, though it has been laid aside between ten and twelve 
years. 
I have chiefly been induced to recall the particulars of this 
subject to mind, by a conversation I lately had with a gentle- 
man from Staffordshire, or Shropshire, who informed me that 
he had laid out between two and three hundred pounds in sur- 
veying instruments of this kind, and yet he had only one on 
which he could depend. 
