Dw amp ewe 
[fy Beg), Tl 
ecseercemet nena See —— 
OBSERVATIONS on the VARIATION of the NEEDLE. 
By Mr. THOMAS HARDING, M.R.1L 4. 
‘THe variation of the Magnetic Needle is meafured by an arch 
of the horizon, intercepted between the true and magnetic me- 
ridian. To account fatisfaétorily for fuch deviation, and ftill 
further for the variation of that deviation, at different times and 
places, has not yet fallen to the fhare of any philofopher, not- 
withftanding the feveral hypothefes framed for the purpofe of 
explaining the phenomena. 
Tue fact is, that bare hypothefes are feldom ufeful (often dan- 
gerous) to fcience. In the prefent cafe, | am perfuaded that we 
{hall never be able to arrive at a true theory of the variation of 
the needle, without the advantage of numerous obfervations made 
at fundry diftant places, at the fame, and alfo at different, times: 
It is therefore much to be wifhed that a correfpondence were 
eftablifhed among the learned, for this and all fuch ufeful pur- 
pofes, and that experience were fubftituted for fyftems founded 
only on conjecture. 
P 2 THE 
Read May 
7) 1791. 
