( ><*5 ) 
The Variation of the Magnetick Needle was obferv’d, 
thisYear, to be 7 0 20' Weft, Thilip Wells, Surveyor 
General of this Province, in the Year 1686, obferv’d it 
to be 8 0 45' \ by which, it appears to decreafe about 
1 0 25' in 38 Years, or a little more than two Minutes- 
in a Year. 
I II .A New Contrivance for taking Levels , by the(Re- 
Verend]o\m Theophilus Delaguliers, L, L . i). 
% S. S. 
HAT the Air Thermometer is alfo a Baro- 
meter, has been obferv’d long ago * and, be- 
caufe the Liquor in it will rife and fall, as well by the 
Change of the Weight of the Air, as by the Air’s Rare- 
faction by Heat and Cold, this Inftrument has no longer 
been made ufe of as a Thermometer, and, in its Read, 
Spirit of Wine Thermometers, hermetically feal’d,have 
been us’d ever fince. 
But, becaufe the Errors of the Air Thermometer (or 
its Difference from the Spirit Thermometer) depend 
only upon the Change of the Weight of the Atmof- 
phere from what it was, when the two Thermometers 
were fet at the fame Degree of their refpe&ive Scales ^ 
the late Dr. Hook contriv’d an Inftrument, that he call’d 
a Marine Barometer, made of a Combination of the two 
abovemention’d Thermometers , in fuch Manner, that 
a third Scale being made ufe of, to obferve the Diffe- 
rence of the two Thermometers, thereby the Change 
of the Air’s Gravit) 7 , and confequently Storms, Rains, 
and fair Weather, might be foretold at Sea, where the 
Quickfilver Barometer becomes ufelefs by the linking of 
the Ship. 
Dr. 
