inotloas, Ceen [n Riversbecaufeof the higher or lower grounds, 
which are found in their Beds, and caufe various windings and 
whirlings in them, poflibly a reafon may be rendred of the many 
difFerencesj obferv'd in the Declination of the Needle ( 
why in fome parts the Needle varies much in a little time 5 why, 
in others , it is alvvayes turning without any ftay , as fome 
fay they have obferv'd^ why the greater alterations are met 
withat'the entring into, and going out of Iflands^) and of 
many other things, we for brevities fake pafs by 5 as wealfo 
omit to deduce from it divers particulars relating to Navi- 
gation. 
Which if it fhould be fo, there would be no hopes of finding 
a tegular Hypothefis for that change, forafmuch as it would de- 
pend from caufes that have no regularity at all in them, as moft 
of the mutations of Nature are. You may only take notice, 
that if there be a proportion between the force of the faid Cur- 
rent^ and the Emb-, that may be able by changing its Bed, re- 
move this from its proper ^fite: Which would produce an al- 
teration in the height of the Pole, as fome think they have 
obferv'd, if that may not be afcribed to a dcfeifi in theOb- 
fervations, of which we may be rendred certain, when 
more exadl ones fliall have been made. And fo , whereas 
others would impute the various Declination of the Magnet 
to the change of the Pole , we ftiould be obliged to attri- 
bute the change of the Poleto the various Declination of the 
Magnet. 
From this Obfervation, which w^as thought fit tobepublilht 
here, Mathematicians are invited from time to time to make the 
like in their Countriesjto fee,whether in this change there be any 
regularity. If it had been obferv'd every Year, we fliould al- ' 
ready know the progrefs thereof, and fee^ whether there were an 
Uniformity^ and in what time the Needle did exa<5ily refped the 
Pole. Wheref re it were very defir>Tble, that for the future, 
they would ufe greater care and diligence^ in making moft ex* 
a(5t Meridians, as well for their own Ohferyations, as for the con- 
veniency or thofe ^ who in their Travels fballhave thecUriofi- 
ly of obferving wiih the Needle it felf, as M. Juzmt defignt^d 
to do in the Cities where he pafs *d, if he had found Meridians 
there, 
