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with Dr. Halley’s for the year 1700, and the prefent 
chart now publishing, compleat fix reviews : Thefe 
are tabulated, and Shew the quantity of the variation, 
at thofe Several periods, to every y degrees of latitude 
and longitude in the more frequented oceans ; which 
we hope will prove acceptable, as nothing of the like 
kind has yet appeared, or can eafily be obtained. 
Our materials have been fo deficient, that even in 
the limits to which our tables are confined, we have 
been obliged to leave blanks in fome of the above 
periods, for want of that concurrent testimony, on 
which the numbers inlerted are founded : but, con- 
fidering the difficulties unavoidably attending a work 
of this fort, and the little afiiStance which we have 
met with from private hands, we hope that this 
Royal Society will not only excufe thofe vacancies, 
but alfo thofe in the great tradts of fea, as well as 
land, concerning which we are very unwillingly 
obliged to be intirely Silent. 
Agreeable to our former addrefs, we lay only 
what appear to be fadts before you, without at- 
tempting to introduce any hypothefis for the folution 
of thefe phaenomena ; fome of which (being very 
extraordinary) we recommend peculiarly to the no- 
tice of thofe gentlemen, who may endeavour the in- 
vestigation of their caufes. 
Under the equator, in longitude 40° E. from Lon- 
don, the highefi; variation during the whole y6 years 
appears to be 17°^ W. and the leaft W.: and 
in latitude i5°N. longitude 6o° W. from London, 
the variation has been constantly y° E. but in other 
places the cafe has been widely different ; for in the 
latitude io° S. longitude 6o° E. from London, the 
variation has decreafed from 1 7 0 W. to 7 i W. , and 
in latitude io° S. longitude 5° W. from London, it 
has 
