[ 879 ] 
variation will (according to their feveral hypothefes) 
be at any given place and time : The above propo- 
rtion, therefore, will (if carried into execution) bring 
thefe feverally to the teft, and enable the judicious 
either to approve or rejedt them ; the writers being 
determined (as was their former plan) to publifli no- 
thing which lhall not be warranted by the real ob- 
fervations, which fhall come into their hands, and 
fhall leave the application thereof (as to each hypo- 
thecs) to others : if any of them fhould be fo far 
confirmed, by this examination and comparifon, as 
to give juft ground for a calculation, their labour 
will be at an end ; but if not, they humbly recom- 
mend the continuance of fuch a periodic operation, 
as they now propofe to undertake, being the only 
means of attaining fuch a deftrable event, and of fup- 
plying the defedt till it can be obtained. 
To whom then can they fo properly apply, as to 
the Royal Society of London, for afliftance, in a 
work of fo much confequence to trade and naviga- 
tion, and from whence fo valuable an addition to 
natural knowledge may poflibly accrue : It has been 
the peculiar honour of the many illuftriou> members 
of this body, that they have deduced their knowlege 
fjom experiments, and not from hypothefes; and 
(as that is the method now propofed) the writers of 
this paper humbly defire of this Society, as a body, 
and of each individual that compofes it, to commu- 
nicate to them fuch obfervations of the variation as 
they have already made within a few years laft paft, 
or fhall hereafter make, before the 2 f th of March 
y 6, either by fea or land 5 and (as all mankind 
are 
