99 
the particles of magnetic bodies, &c. 
The quotients in the 5th column alford the best estimate of 
the degree of coincidence between the observed and computed 
values of u, since the magnitude of the errors to which the 
observations are liable depends upon the magnitude of a. 
The greatest discordance between the observed and computed 
values of a, whether estimated by their actual difference, or 
by dividing this difference by the computed value of a, is that 
corresponding to the least distance of the ring from the 
magnets ; but even this amounts to little more than a fortieth 
of the whole. Perhaps it would have been as well to have 
omitted this observation altogether, since the distance of the 
ring from the magnets was so small, that supposing that 
distance to have been -51 inch instead of '50, or that an error 
of 'oi was made in estimating it, the difference between the 
observed and computed values of cc would have been — 39*4 
instead of + 53’4. Having however made the observations 
with great care, from this close agreement between the values 
of « deduced from the formula. 
M 
{p + c)^ + 
y 
and those observed, I cannot but conclude that this formula 
is correct. 
If we were to suppose that 
then 
u 
f 
M‘ 
\ p + c 
M’ = 
c, — c 
I m 
m 
where a^ 
Combining the observations as I have already mentioned, 
I obtained the mean values M' = 5-060 and p ==. -240. From^ 
