[ 4 2 ? ] 
frequently happens by an cbfcure Horizon, and con- 
fequently to be of great Ufe in Navigation. 
From on board his Majefiy’s 
Ship Oxford, at Spithead, 
March io. 1738. 
Signed, 
Thomas Strachey, firji Lieutenant . 
Thomas Griffin, Lieutenant. 
James Irving, Majler. 
Wi liam Slanning, Jecond Majler. 
Note, The Latitude of Spithead the 
neareft is about .... 
}?o 46 
North* 
Directions concerning the Quadrant, 
T H E Alteration made in this Inftrument is greatly 
for the better, for the Level of Water'requir’d 
to be t rim'd every Time of Obfervation, befides the 
Hazard of fpilling the Water from a great Motion; 
but in this Level of Mercury, the firft Trimming ferves 
always, and without hazard of fpilling, being clofe 
confin'd, as will be feen in the Inftrument.-— The 
Cylinders are made large enough to receive the Air 
that will becondens’d and rarefied alternately by the vi- 
bratory Motion of the Quickftlver through the frnali 
glafs Tubes, without affe&ing the true Level Line, 
.as will be found upon Trial: Notwithftanding, the 
Hi 2 included 
