GUNNERY, 
the art of gunnery, but such as have taken 
the said oath. 
GUNNERA, in botany, so named in ho- 
nour of J. E. Gunnerus, Bishop of Dront- 
heim, in Norway, a genus of the Gynandria 
Diandria class and order. Natural order 
of Urticas, Jussieu. Essential character : 
amfcnt with one-flowered scales ; calyx and 
corolla none ; germ two-toothed ; styles 
two ; seed one. There is but one species, 
viz. G. perpensa, marsh marygold-leaved 
gunnera. Native of the Cape. 
GUNNERY, is the art of determining 
the course and directing the motion of bo- 
dies shot from artillery, or other warlike 
engines. . 
The great importance of this art is the 
reason it is distinguished from the doctrine 
of projectiles in general ; for it is no more 
than an application of those laws which 
all bodies observe when cast into the air, to 
such as are put in motion by the explosion 
of guns or other engines of that sort. And . 
it is the same thing whether it is treated in 
the manner of projectiles in general, or of 
such only as belong to gunnery ; for from 
the moment the force is impressed, all 
distinction with regard to the power which 
put the body first in motion is lost, and it 
can only be considered as a simple projec- 
tile. See Projectiles, 
Prob. I. The impetus of a ball, and the 
horizontal distance of an object aimed at, 
with its perpendicular height or depression, 
if thrown on ascents or descents, being 
given, to determine the direction of that 
ball. 
From the point of projection A (Plate VI. 
Miscell. fig. 8, 9, 10, 11,) draw Am repre- 
senting the horizontal distance, and B m 
the perpendicular height of the object 
aimed at : bisect A m in H, and AH in f- 
on H and / erect H T,/F perpendicular to 
the horizon, and bisecting A B the oblique 
distance or inclined plane in D, and A D in 
F. On A raise the impetus A M at right 
angles with the horizon, and bisect it per- 
pendicularly in c, with the line G G. Let 
the line A C be normal to the plane of pro- 
jection A B, and cutting G G in C ; from 
C as centre, with the radius CA, describe 
the circle AGM cutting if possible the 
line F S in S, s, points equally distant from 
G ; lines drawn from A through S, s, will be 
the tangents or directions required. 
Continue AS, A s to T, t ; bisect D T, 
D t, in V, v ; and draw lines from M to 
S, s ; then the angle ASF= angle MAS 
ys angle A M s s= angle sAF; and for the 
same reason angle A s F = angle M As — 
angle AMS = angle SAF; wherefore 
the triangles MAS, S A F, s A F are simi- 
lar, and AM;Ai:: As:sF = t«; con- 
sequently AT is a tangent of the curve 
passing through the points A, v, and B ; 
because t v z= v D, A D is an ordinate to 
the diameter TH, and where produced 
must meet the curve to B. 
In horizontal cases (fig. 10.) v is the 
highest point of the curye, because the 
diameter TrH is perpendicular to the ho- 
rizon. 
When the mark can be hit with two di- 
rections (the triangles SAM, s A F being 
similar) the angle which the lowest direction 
makes with the plane of projection is equal 
to that which the highest makes with the 
perpendicular A M, or angle s A F = angle 
SAM. And the angle S A s, compre- 
hended between the lines of direction, is 
equal to the angle S C G, and is measured 
by the arch S G. 
When the points S, s coincide with G, 
or when the directions A S, As become 
A G; (fig- 11.) A B will be the greatest dis- 
tance that- can be reached with the same 
impetus on that plane ; because S F coin- 
ciding with G g the tangent of the circle 
at G, will cut off A g a fourth part of the 
greatest amplitude on the plane A B. The 
rectangular triangle m A B, c A C are simi- 
lar, because the angle of obliquity m A B 
— c AC; wherefore m A : m B : : one-half 
impetus : c C, and »» A : A B i ; A c ; AC, 
Horizontal Projections (ibid. fig. 10, 11.) 
When the impetus is greater than half 
the amplitude, there are two directions, 
T A H, and t A H for that amplitude ; when 
equal to it, only one ; and when less, none 
at all ; and conversely. For in the first 
case the line FS cuts the circle in two 
points S, s, in the second case it only touches 
it, and in the last it meets not with it at all ; 
and conversely, When there is but one di- 
rection for the amplitude A m, the angle 
of elevation is 45° ; and when the angle of 
elevation is of 45° A in is the greatest ampli- 
tude for that impetus, and equal to twice 
the impetus. The impetus remaining the 
same, the amplitudes are in proportion to 
one another as the signs of double the 
angles of elevation,’ and conversely. For 
drawing s N (fig. 10) parallel and equal to 
A F a fourth part of the amplitude, and 
supposing lines drawn from s to the points 
C and M, the angle ACs=jAMs = 
2 s A F ; therefore N s, the sine of A C s is 
