160 
MINUTES OF PROCEEDINGS OF 
and if a represent the constant angle of half-oscillation, and x the angle 
variable with h, we shall have 
therefore 
h —l {cos {a — x) — cos a} ; 
v = \/ %gl {cos (a — x) — cos a}, 
v = ~ v/ 2 {cos (« — x) — cos a }. 
If T be the time occupied by the pendulum l , in describing a whole 
revolution, the motion being supposed to be uniform, 
T— — , 
v 
or T = 
2 1 
2 s/ {cos (a —• x) — cos a] 
And, in general, if T be the time which the pendulum takes to pass 
through an arc contained K times in the circumference. 
T = 
2 1 
K v/2 {cos (a — x) — cos a } * 
But in Navez^s apparatus the constant angle of half-oscillation =75°; 
therefore 
T = 
_ U _ 
KV 2{cos (75°—^)—cos 75°} * 
The values successively given to x correspond to the middle of each arc; 
thus in calculating a table when the arcs are made equal to 1°, the values 
of x are made J°, 1J°, 2|°, &c., and it is assumed that each arc is passed 
through with a velocity equal to that acquired in the middle of the arc. 
This method of calculation of Major Navez is not strictly correct, but the 
small loss of time resulting from his method never affects those arcs 
comprised in the space {A! — A), and may practically be considered nil. 
Tables calculated by this means will be found in Captain Noble's Report, 
Appendices III. and IY. pp. 148,149. 
Description of the arrangements at Shoehuryness for carrying on experiments 
with Navez’s Electro-Ballistic Apparatus. 
18. The instrument room at Shoeburyness is constructed in the lower 
story of the tower, used in supplying the barracks with water. No pains 
have been spared to make this room as complete as possible. It is 
lighted by three large windows, and has a stove in which a fire is 
