amination of harbours, coasts, soundings, 
•Stc. we refer to Surveying. 
Under the article Quadrant the mode 
of taking observations at sea will be given, 
for ascertaining the latitude by solar obser- 
vation. 
NAUSEA, in medicine, a reaching, or 
propensityand endeavour to vomit, arising 
from a loathing of food, excited by some 
viscous humour that irritates the stomach. 
NAUTILUS, in natural history, a genus 
of the Vermes Testacea class and order. 
Shell univalve, divided into several depart- 
ments, communicating with each other by 
an aperture. There are more than thirty 
species, separated into sections. A. Spiral, 
rounded, with contiguous whorls. B. Spiral, 
rounded, with separated whorls. C. Elonga- 
ted and straightish. N. porapilius, inhabits 
the Indian and African oceans ; often very 
large, and finely variegated with brown 
flexuous streaks, spots, and marks, under 
the outer covering, which is vVhite ; within 
of a most beautiful pearly gloss. Of this 
species, the inhabitants of the east make 
drinking cups. N. spicula, aperture of the 
shell orbicular ; whorl cylindrical ; it inha- 
bits the American and Indian oceans ; about 
an inch in diameter; whitish within, shining 
like mother-of-pearl; orbicular; the whorls 
gradually decreasing inwards, the first a 
little straight; siphon contiguous to the walls 
of tlie shells. 
NAVY, the fleet or shipping of a prince 
or state. 
The management of the British navy 
royal, under the Lord High Admiral of 
Great Britain, is entrusted to principal offi- 
cers and commissioners of the navy, who 
hold their places by patent. The principal 
officers of the navy are four; viz. the Trea- 
surer, whose business it is to receive money 
out of the exchequer, and tO pay all the 
charges of the navy, by warrant from the 
principal officers; Comptroller, who attends 
and comptrols all payment of wages, is to 
know the rates of stores, to examine and 
audite all accounts, &c. : Surveyor, who is 
to know the states of all stores, and see 
wants supplied, to estimate repairs, charge 
boatswains, &c. willi what stores they re- 
ceive, and at the end of each voyage to state 
and audite accounts : Clerk of the Acts, 
\Vhose business it is to record ail orders, 
contracts, bills, warrants, &c. 
The Commissioners of the navy are five : 
the first executes that part of the Comptrol- 
ler’s duty which relates to the comptrolling 
the Victuallers’ accounts ; the second, an- 
other part of the said Comptroller’s duty, 
relating to the account of the store-keeper.s 
of the yard ; the third has the direction of 
the navy at the port of Portsmouth ; the 
fourth has the same at Chatham ; and the 
fifth at Plymouth. 
Ehere are also other Commissioners at 
large, the number more or less, according 
to the exigencies of public affairs ; and since 
the increase of the royal navy, these have 
several Clerks under them, with salaries 
allowed by the King. 
'1 he victualling of the royal navy had for- 
merly been undertaken by contract, but is 
now managed by Commissioners, who hold 
their office at Somerset House, Strand. 
NEBULiE, in astronomy. There arc 
spots in the heavens called nebulze, some of 
which consist of clusters of telescopic stars, 
others appear as luminous spots of diflFerent 
forms. The most considerable is one in the 
midway between the two stars on the blade 
of Orion’s sword, marked &■ by Bayer, dis- 
covered in the year 1656 by Huygen’s ; it 
contains only seven stars, and the other part 
is a bright spot uptm a dark ground, and 
appears like an opening into brighter re- 
gions beyond. 
Dr. Halley and others liave discovered 
nebula; in dilferent parts of the heavens. 
In the “ Connoisance des Temps,” for 1783 
and 1784, there is a catalogue of 103 ne- 
bula;, observed by Mes.sier and Mechain. 
But to Dr. Herschel we are indebted for 
catalogues of 2000 nebula;, and clusters of 
stars, which he himself has discovered. Some 
of them form a round compact system, 
others are more irregular, of various forms, 
and some are long and narrow. The glo- 
bular systems of stars appear thicker in the 
middle than they woidd do if the stars were 
all at equal distances from each other; they 
are, therefore, condensed toward the cen- 
tre. That stars should be thus accidentally 
disposed is too improbable a supposition to 
be admitted ; he supposes, therefore, that 
they are brought together by their mutual 
attractions, and that the gradual condensa- 
tion towards the centre is a proof of a cen- 
tral power of such a kind. He observes 
also, that there are some additional circum- 
stances in the appearance of extended clus- 
ters and nebulae, that very much favour the 
idea of a power lodged in the brightest 
part. For although the form of them be 
not globular, it is plain that there is a ten- 
dency to sphericity. As the stars in the 
same nebulae must be very nearly all at the 
same relative distances from us, and tliey 
R r .2 
