I N S 
I N S 
I N T 
extent between the first and second terms, 
you place one foot of the compasses on the 
third term, then turning the compasses about, 
the other foot will tail on the fourth term 
sought. 
r i has in example T, of tire three given 
numbers 4, 7, and 16 , if you take the ex- 
tent from 4 to 7 in the compasses, and place 
one foot in 16, the other will fall on 28 the 
answer, in the line of numbers marked n. 
Again, the artificial lines of numbers and 
sines, are used together in plain trigonome- 
try, as in example 3, where the two angles 
B and C, and the side AB are given ; for here 
if you take the extent of the two angles 53° 
30 and 36° 30' in the line of sines marked s, 
then placing one foot upon 230 in the line 
of numbers n, the other will reach to 170, 
19 the answer. 
Also the lines of numbers and tangents are 
used conjointly, as in the example 4, for take 
in the line of tangents t, the extent from 45° 
{radius) to 36° 30 ; that will reach from 230 
to 170, f9 the answer as before. 
Lastly, the artificial lines of sines and tan- 
gents are used together in the analogies of 
spherical triangles. 
Thus example 6 is solved by taking in the 
line of sines .v, the extent from 90° (radius) 
to 36° 15', then that in the line of tangents t, 
will reach from 42° 34' to 28° 30, the answer 
required. 
We shall only further observe that each pair 
of sectoral lines contain the same angle, viz. 
6 degrees in the common 6-inch sector ; 
therefore to open these lines to any given 
angle, as 35° for instance, you have only to 
take 35° laterally from the line of chords, 
and apply it parallelwise from 60° to 60° in 
the same lines, and they will all be opened 
to the given angle of 35°. 
If to the angle 33° you add the angle 6°, 
which they contain, the sum is 4l°: then 
take 4l° laterally from the line of chords, and 
■apply it parallelwise, from 60 to 60, then will 
the sides or edges of the sector contain the 
same angle of 3 5 degrees. 
Of proportional compasses. Though this 
sort of compasses does not pertain to a com- 
mon case of instruments, yet a short account 
of their nature and use may not be unaccept- 
able to those who are not acquainted with 
them. They consist of two parts or sides of 
brass, which lie upon each other, so nicely 
as to appear but one when they are shut. 
These sides easily open, and move about a cen- 
tre, which is itself moveable in a hollow canal 
■cut through the greatest part of their length. 
To this centre on each side is affixed a sliding 
pieoe of a small length, with a fine line drawn 
on it serving as an index, to be set against 
other lines or divisions placed upon the com- 
passes on both sides. These lines are : 1 . A 
line of lines. 2. A line of superficies, areas, 
or plans. 3. A line of solids. 4. A line of 
circles, or rather of polygons to be inscribed 
in circles. 
These lines are all unequally divided, the 
three first from It© 10, the last from 6 to 
20; their uses are as follow: 
By the line of lines you divide a given 
line into any number of equal parts ; for by 
■placing the index against 1, and screwing 
it fast, if you open the compasses, then the 
distance between the points at each end 
will be equal. If you place the index against 
2, and open the compasses, the distance be- 
tween the points of the longer legs will be 
twice the distance between the shorter ones ; 
and thus a line is bisected, or divided into 
two equal parts. If the index be placed 
against 3, and the compasses opened, the 
distances between the points will be as 3 to 
1, and so a line is divided into three equal 
parts ; and so you proceed for any other 
number of parts under 10. 
The numbers of the fine of plans answer to 
the squares of those in the line of lines ; for 
because superficies or plans are to each other, 
as the squares . of their iike sides, therefore 
if the index be placed against 2 in the line of 
plans ; then the distance between the small 
points will be the side of a plan whose area is 
i ; but the distance of the larger points will 
be the like side of a plan whose area is 
2, or twice as big. If the index be placed at 
3, and the compasses opened, the distances 
between the points at each end will be the 
like sides of plans, whose areas are 1 to 3, and 
so of others. 
The numbers of the line of solids answer 
to the cubes of those in the line of lines; be- 
cause all solids are to each other as the cubes 
of their like sides or diameters ; therefore, if 
the index be placed to No. 2, 3, 4, &c. in 
the line of solids, the distances between the 
lesser and larger points will be the like sides 
of solids, which are to each other as 1 to 2, 
1 to 3, 1 to 4, &c. For example, if the in- 
dex be placed at 10, and the compasses be 
opened, so that the small points may take the 
diameter of a bullet weighing 1 ounce, then 
the distance between the larger points will 
be, the diameter of a bullet or globe of 10 
ounces, or which is lO.timesas big. 
Lastly the numbers in the line of circles are 
the sides of polygons to be inscribed in a 
given circle, or by which a circle maybe di- 
vided into those equal parts from 6 to 20. 
Thus if the index be placed at 6, the points 
of the compasses at either end, when opened 
to the radius of a given circle, will contain 
the side of a hexagon, or divide the circle 
into 6 equal parts. If the index be placed 
against 7, and the compasses opened, so that 
the larger points may take in the radius of 
the circle ; then the shorter points will di- 
vide the circle into 7 equal parts for inscrib- 
ing a heptagon. Again, placing the index 
to 8, and opening the compasses, the larger 
points will contain the radius, and the lesser 
points divide the circle into 8 equal parts, 
for inscribing an octagon or square. And 
thus you proceed for others. 
Instruments, surgical. A case of pocket 
instruments for surgeons, which they ought' 
always to carry about with them, contains lan- 
cets of different sizes; scissars fit for several 
uses ; forceps, plain and furnished with teeth ; 
incision-knives, straight and crooked ; a spa- 
tula, probes, needles, &c. See Surgery. 
INSURANCE, ea ws of. Insurance is 
regarded by the law as a contract between two 
or more parties ; that on one paying a certain 
premium he shall be indemnified or insured 
against certain risks set forth in the policy. 
This is extremely convenient in commerce, 
but was made use of as a kind of gambling 
till the statute 14 Geo. III. c. 48, that no 
insurance shall be made on fives, or on any 
other event, wherein the party insured hath 
no interest; that in all policies the name of 
such interested party shall be inserted, and 
nothing more shall be recovered thereon than 
2 7 ' 
the amount of the interest of the insured. 
This, however, does not extend to marine in- 
surances. But as it was a common practice 
ot insuring large sums without having pio- 
perty on board, and which were called wager 
policies or insurances, interest or no interest, 
and ot insuring the same goods several times 
over, it was enacted, that all insurances, in- 
terest or no interest, or without further proof 
ot the interest than the policy, or by way of 
gaming, or without benefit of salvage to the 
insurer, should be void, except on privateers, 
or on ships or goods from the Spanish o'r 
Portuguese dominions ; and that no re-assu- 
rance shall be legal, unless the former insurer 
be insolvent or dead ; and that in the East 
India trade the lender of money on bo tomry, 
or at respondentia, shall alone have a right to 
be insured for the money lent ; and the bor- 
rower shall recover no more upon any insu- 
rance than the surplus of his bottomry or 
respondentia bond. No insurance can be 
made on any illegal voyage. 
It is generally stipulated in policies that the 
insurer shall not be answerable for any partial 
loss on certain articles, but on others less dif- 
ficult to be preserved at sea, but liable to 
partial injuries, squill be liable for any partial 
loss above five per cent. ; and as to all other 
goods, and the ship and freight, he shall only 
be liable for such losses above three per cent. 
But lie is liable on all losses, however small* 
called general average or losses occasioned 
by the ship stranding ; but this loss must be 
an immediate, not a remote, consequence of 
the stranding. 
The commencement of the risk on the ship 
varies in most cases, and usually continues till 
the ship has been 24 hours at safe anchor. 
Up®n goods it commences when they are on 
board, and continues till they are removed or 
landed. 'I lie ship insured must be sound, 
and in every respect fit to bear the sea, and 
perform the voyage ; and if she deviates from 
the usual course, and stops at places not usu- 
ally stopped at, without a proper cause, the 
contract is void. 
Insurance upon life is a contract by which 
- the insurer, for a certain sum proportioned to 
the age, health, and profession of the person 
whose life is to be insured, engages that the 
person shall not die within a certain period, 
or if he do, the underwriter will pay a sum 
of money to the person to whom the policy 
is granted. 
Insurance against fire. The insurer un- 
dertakes, in consideration of a premium, to 
indemnify the insured against all losses by 
fire which he may sustain in his house or 
goods during the time mentioned in the po- 
licy. 
INTAGLIOS, precious stones on which 
are engraven the heads of great men, inscrip- 
tions, and the like; such as we frequently see 
set in rings, seals, &c. 
INTEGER, in arithmetic, a whole num- 
ber, in contradistinction to a fraction. 
INTERCALARY, in chronology. See 
Bissextile, &c. 
INTERCOMMONING, in law, is when 
the commons of two manors lie together, 
and the inhabitants of both have, time out of 
mind, caused their cattle to feed promiscu- 
ously on them. 
IN r I ERCOSTAL. See Anatomy. 
INTERDICT, an ecclesiastical censure* 
