88 
GOODMAN : APPARATUS FOR BORE HOLES. 
of the hemispherical cap, it bears with its circular rim against 
the same ; the contact of the rim and hemispherical cap taking 
place at the same instant all round the rim of the plunger, and 
not at one part before the other. 
A helical or other spring surrounding the spindle bears 
with its lower end against the upper side of the presser or enlarged 
head of the plunger, and with its upper end against the under- 
side of the clockwork base plate. 
The end of the plunger projecting above the clockwork 
base plate is connected with a trigger or other release device, 
operated by clockwork mounted on the clockwork base plate. 
Wlien the plunger is raised by pulling up the presser spindle 
and compressing the spring, the cone is released so as to swing 
freely on its pivot support, and the spindle is held raised by 
a catch device or a wound-up cord or chain. The clockwork is 
set for a given time of release and set going, so that when the 
time elapses the catch is released, allowing the plunger to be 
pushed down by the spring. In the case of a wire wound on 
a barrel, the clockwork device may be arranged to allow the 
plunger to move slowly downwards as the wire gradually unwinds 
from the barrel, coming in contact with the hemispherical cap 
after the lapse of a given time interval. 
The apparatus is fitted and carried in a hermetically closed 
tube, attached to a rope or rods for being lowered into the bore 
hole. 
The apparatus is lowered into the bore hole with the 
pendulum swinging freely on its support, and the magnet free 
to swing into the magnetic meridian, turning the pendulum with 
it, and with the clockwork release apparatus set to allow ample 
time for the apparatus to be lowered, and for the pendulum and 
magnet to come to rest. It will be evident that under these 
conditions the angle of inclination to the vertical of the bore 
hole will be the same as the angle between the plane of the base 
of the cone pendulum and the base plate below it ; whilst the 
angle between the direction or line of greatest inclination of 
the base of the cone pendulum to the base plate, and the direction 
of the magnet will give the horizontal direction of the deviation 
of the bore hole from the vertical. 
