SUR 
fanee, and th« two angles they mutually form 
with C being ascertained by the graduated 
edge of the instrument ; it follows that the 
intersection of the two sights, from B to C, 
and from A to C, will determine the exact 
locality of C ; let the line B C be measured 
on the same scale from which BA was 
taken, and it will show the distance of C 
from B. In this manner the whole horizon 
may be surveyed from the base line A B ; 
except such parts as may lay in, that is, 
occupy the same direction therewith. And 
it is to be observed, that in laying a base 
line, the nearer the angle of intersection, as 
at C, is to a right angle, the more exactly 
will the distance be denoted. Hence a 
great extent of base line is to be preferred, 
when at command ; and, if practicable, no 
angle under'twenty degrees should be made : 
it is always better to take a new station 
than to make acute angles with the object 
to be surveyed ; which may, for the most 
part, be easily avoided in horizontal sights; 
but in vertical observations, very acute an- 
gles will ordinarily occur. 
Thus, in Proposition X, “ which relates to 
ascertaining the heights of P and 0 ,(fig. 12) 
from the level of C, and the distance ofC from 
B, cannot be effected but by acute angles." 
Here, in lieu of laying the base line, AB, 
as nearly as possible square with the point 
C, we place it in, the exact direction there- 
with. Then, after taking the angles of ele- 
vation from the horizon at the station B, to 
the two points O and P, and measuring the 
e^act length of the base line A B, the in- 
strument is removed from B to A ; where 
two more sights are taken to O and P. We 
have thus the two angles, PB A and P A B, 
determining the locality of P; and the two 
angles, O B A and O A B, determining the 
locality of O. Now the line, BA, being 
prolonged, and the perpendicular, P O, be- 
ing likewise continued, will intersect in C. 
The lines, P B, O B, and C B, being mea- 
sured on the same scale whence the base 
line, A B, was taken, the altitudes of P and 
of O, with their intermediate distance, will 
be given ; while the distance of C from B 
will be exhibited. 
We shall conclude this article with a few 
words on the manner of carrying a line of 
sight over a hill, as is often done for the for- 
mation of a road, or for the conducting a 
canal over a rising ground ; in which cLe 
tlie level must be preserved. 
Proposition XL “ To carry a line of 
sight, 01- a level, in the direction of A B 
over the rising ground C.” Ascertain where 
SUS 
the line of sight strikes the hill at e; carry 
the instrument to that point, and, in the 
exact direction of the former sight, take a 
second sight from e to a, or to any conve- 
nient spot, where a pole and target should 
be fixed. See Levels. As this survey for 
a canal is to be taken by means of a spint 
level, the exact attitude of each sight must 
be taken, by noting the height of the target 
from the plain, A B, at every sight, or by 
following up a regular succession of levels, 
each of which will be the height of the in- 
strument above the last. Thus the hill will 
be ascended : the descent on the other side 
is effected by the inversion of the fore- 
going mode ; always taking the descending 
levels of the target for canals ; but for 
loads, or for laying down a meridional line, 
when once the summit is gained, a long 
sight may be taken to a distant object: 
this subject is pleasingly exemplified in a 
nevv work published by Longman and Co. 
entitled “ Mathematics simplified, and prac- 
cally illustrated,” in which a great variety 
of instructive and useful matter will be 
found, together with the description of a 
new instrument, on a very simple construc- 
tion, said to be equal to every branch of 
surveying. 
SUS, the hog, in natural history, a genus 
of Mammalia, of the order of Beliii®. Ge- 
neric character : four front teeth in the up- 
per jaw, converging ; six in the lower, pro- 
jecting ; two tusks in the upper jaw, short; 
two in the lower standing out ; snout trun- 
cate, prominent, and moveable: feet cloven. 
These animals are allied by their teeth to 
the carnivorous quadrupeds, and by their 
cloven feet to the ruminating ones. Tliey 
feed almost indifferently upon animal and 
vegetable substances, devouring with avidi- 
ty what is most nauseous and disgusting. 
Tliey use their snout for digging up the 
ground in quest of roots, are fond of rolling 
and wallowing in mud, and are distinguished 
by extreme fecundity. There are six spe- 
cies, of which the following are the most 
important ; 
S. scroft, the common hog. All the va- 
rieties of this animal originate in the w>ild 
boar, which is found in most of the tempe- 
rate regions of Europe and Asia. It is 
smaller than the domesticated animal, and 
uniformly of a dark grey colour, approach- 
ing to black. It is armed with formidable 
tusks, sometimes ten indies, or even more, 
in length ; those in the under jaw curviuK in- 
wards, and capable from their size, strength, 
and sharpness, of inflicting the most dread- 
