( i<*7 ) 
decs" ex metallis ; de aftione ejus in metalla; de 
m eta 11 is ipfis ; qus in adverfaria redegi. Otium nac- 
tus forte evulgabo : ut raoniti parcant vano labori, <3c 
fumtibus. Valete ! 
■ ■ * .. 
[' ' f. . ' f . j ' ; . " . . . • ' ; f ’ 
II. A Spirit Level to be fixed to a Quadrant 
for taking a Meridional Altitude at Sea, when 
the Horizon is not vifible. <By John Hadley, 
Efq 5 V. Pr. (11. S. 
T HE Neceffity of feeing the Horizon, in order to 
find the Latitude of a Ship at Sea, has always 
been fo great an Inconvenience, that any Method for 
determining it without the Help of the Horizon, will 
be of confiderable Ufe, although it fhould be liable 
to an Error of a few Minutes : And as it is generally 
agreed by Seamen, that they are much oftner fenfible 
of this Inconvenience in calm Weather,than in rough ; 
- it is hoped that the following manner of conftrufting • 
and ufing a Spirit Level, may, in that Cafe, be capa- 
ble of fo much Exactnefs, at leaft, as may render it 
acceptable to the Pubiick. Fide Fig. i. 
This Level is compofed of a Glafs Tube A B, 
bent into an Arch of a Circle, and containing fuch 
Number of Degrees as will be mo ft fuitable to the 
Degree of Exaftnefs with which the Obfervation can 
be made. The Bore of it muft not be wider than 
one Tenth of an Irrch in Diameter, that the Liquor 
1 in 
