COAST. I ARTILLERY JOURNAL, - Air Defense Artillery

480 THE COAST ARTILLERY JOURl'\AL
with the base line so that it could be used correctly to lay the gun in direction
for indirect fire.
The Target.-On one side of the pond. a pole was erected to which a large
pulley was fastened. On the other side of the pond, a home.made windlass was set
up. Ordinary outside twisted pair was reeved through the pulley around the wind.
lass making an endless belt of wire which sagged down under the surface of the
water. Had the wires remained above the water, they would be cut by bullets. A
small pyramidal target was then constructed to scale and tied to the splice of the
wire belt with a rope long enough to permit the target to fioat properly. To pro.
duce the moving floating target effect, a student is equipped with a watch with a
conspicious second hand and instructed to turn the windlass so many revolutions
per minute.
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The Sight.-A Scott sight has been clamped to the Depression Position
Finder for use in laying the gun in direction in Case II.
Tide Scale.-The pond. like most rivers and oceans. due to varying rainfall
and other causes. rarely has the same height of tide. It was therefore necessa,;,
to install a tide scale. The norma] was taken at 2'.0 and readings made possible
from 0:0 to 4:8. At the beginning of every drill the height of tide is read and
telephone.d to the plotting room.
Chart for Range Board.-A chart for the range board was constructed with
corrections for tide. wind. atmosphere. and velocity. :"\ine hundred is taken as
the norma] velocity. with cunes from 800 to 1000. Sixteen is normal for atmos.
phere with cun-es from 0 to 32. Fifty is the normal for the wind with cun-es
from 0 to 100.
Changes in Deflection Board.-A drift scale and range-time scale were im.
Jlrovised on a sheet of tin and used on the deflection board.
It can now readily be seen that all that is necessary to simulate the actual
conditions of a seacoast fire adjustment problem is to man the equipment described