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XLI. A Letter to the Right Honourable the Earl of Macclesfield, Prefdent , the Coun- cil, and Fellows, of the Royal Society, concerning the V ariation of the Magnetic Needle with a Sett of Tables annexed-, which exhibit the Rejult of upwards of Fifty Thoufand Obfervations , in Six perio- dic Reviews, from the Year 1700 to the Year 1756, both inclufive ; and are ad- apted to every Five Degrees of Latitude a 7 id Lo?igitude in the more frequented Oceans. By William Mountaine and James Dcdfon, Fellows of the Royal So- ciety .
Dated London, Nov. 9th. 175 7.
SIRS,
Read Nov. 10. N the 20th of March 1755, we
V s _ > / presented an addrefs to this illus- trious Body, intituled, “ An Attempt to point out, <c in a concife manner, the Advantages which would “ accrue from a periodic Review of the Variation of “ the Magnetic Needle, throughout the known World ; <c requefting contributions thereto, by communicat- “ ing fuch obfervations concerning it, as had then “ been lately made, or could be procured from cor- “ refpondents in foreign parts.”
This addrefs was read at the fame time, and af- terwards honoured with a place in the Tran factions, vol. xlviii. part ii. for 1754.: which favour we now acknowlege in the mod grateful manner ; and, pur-
Vol. 50. U u fua«t
