4 o 
Mr. Huddart’s Observations 
standard for moisture in the atmosphere, and shew the varia- 
tions near the surface of the ocean, which certainly must be 
taken into the account, (evaporation going on quicker in a dry 
than a moist atmosphere,) the theory might still be incomplete 
for correcting the tables of the dip. I shall therefore conclude 
this paper, by shewing a method I used in practice, in order to 
obviate this error, in low latitudes. 
When I was desirous to attain more accurately the latitude 
of any head land, &c. in sight, I frequently observed the an- 
gular distances of the sun’s nearest limb from the horizons, 
upon the meridian both north and south, beginning a few 
minutes before noon, and taking alternately the observations 
each way, from the poop, or some convenient part of the ship, 
where the sun and the horizon both north and south were not 
intercepted ; and having found the greatest and least distances 
from the respective horizons, which was at the sun’s passing 
the meridian, and corrected both for refraction, by subtracting 
from the least, and adding to the greatest altitude, the quan- 
tity given by the table; and also having corrected for the error 
of the instrument, and the sun’s semidiameter; the sum of these 
two angular distances, reduced as above, — 1 8o°, is equal to 
double the dip, as by the following 
