1Q5 KirKERKNCES IN THE MAGNETIC NEEDLE, 



magnetic poles upon a coinpafs placed upon or in ihe bin- 

 nacle. 



If Ihel'e fuppofitions are confiftent with the laws of mag- 

 netifm, eflablitlied by experiments, I judge that they will 

 account for all the differences above noticed ; for the interfe- 

 rence will neceflarily be moft perceptible upon a contpafs 

 when the attradive point is at right angles to the magnetic 

 meridian, that is, when the (hip's head is eaft or weft, and will 

 altogether vanifli or become imperceptible when the attradive 

 point and meridian coincide, or when the fliip's head is north 

 Infiwencpi from or foutb. That the power of this point Qiould become lefs as 

 the laft fuppafi- ^j^g ^^jp ;,i(^ft;afes her diftance from the magnetic pole has not 

 indeed entered into my fuppofitions ; but it may probably be 

 true, and is indeed almoft a neceflary confequence of the 

 that the »S&&s fecond fuppofttion. If the above hypothefis, fo to call it, be 

 ihould have a ^^^^ -^ ^^^^^ follow, that the difFerences in the variation of the 



contrary direc- , /• 



tjon in north magnetic needle, aiifing from a change in the ftiip's head, 

 latitude. ought to be diredly contrary to thofe before recited, when the 



fliip is on tlie north fide of the magnetic equator, for the 

 north point of the needle (hould then be attraded, and 

 the fouth end repelled. I have no obfervatlons which are very 

 decifive upon this head, but thofe that were taken on board 

 the Inveftigator feem to befpeak that as it is fo; they are as 

 follow. 



TABLE 



