THE EOTAL ARTILLERY INSTITUTION. 
271 
RELATION OF THE POWER TO THE WEIGHT IN THE VARIOUS MACHINES, 
IN GENERAL USE, FOR THE MOUNTING, MOVING, AND TRANSPORTING, 
OF THE HEAVY ORDNANCE, CARRIAGES, AND PLATFORMS IN THE 
SERVICE. 
COMMUNICATED BY CAPTAIN H. W. BRISCOE, R.A. 
A full description of tlie different machines and carriages, for the above- 
mentioned purposes is contained in the “ Manual of Artillery Exercises,” but 
thinking that the relation of the power to the weight, on purely mechanical 
principles, and the dimensions necessary for these calculations, may be useful 
to many artillery officers as a reference, I have selected the following paper 
from the course of instruction in Artillery at the R. M. Academy, hoping it 
may prove acceptable. 
Lifting Jack [newpattern). 
Length of lever from centre of screw = 3' 4". 
Diameter of screw = 2J". 
Distance between threads = . 
In this case if P = the power applied at end of lever, 
and W = the weight to be raised. 
Then P : W :: distance between threads : circumference of circle de¬ 
scribed by lever. 
/. P : W :: 1 : 1005*312. 
New Pattern Elevating Screw . 
Length of lever = 2' 1". 
Diameter of screw = 2J". 
Distance between threads = J". 
P : W :: 1 : 628*32. 
Crab Capstan, 
Mean diameter of windlass = 10". 
Actual length of capstan bars = 16'. 
Effective length of do = 12'.* 
Taking diameter of fall = 1". 
or P : W :: 1 : 13. 
* The power is not applied at the extremity of the bars, but is distributed over a space of 4 ft. 
from each end by two men, each occupying a space of 2 ft. The mean of this distance is taken, 
which will give the power applied at a distance of two feet from each extremity, consequently 
making the effective length of bar or lever = 12'. 
