HAYES AND 
KENNEDY. 
METHODS OF DRILLING. 167 
over a pully at the top of the derrick and thence by block and fall to 
a swivel attached to the top of the drill rod, the descent of the latter 
being controlled by the driller by means of a feeding device. The 
lower end of the drill rod is supplied with one of several forms of bit, 
adopted to the kind of material being drilled. The material loosened 
by the rotating bit is carried upward to the surface by the water 
ascending on the outside. This ascending current of water keeps the 
hole clean and allows the drill rod to turn freely. It is essential that 
the now of water should be continuous, and a drilling outfit is always 
supplied with two force pumps in order to avoid any danger of stop- 
ping the flow. If the well has passed through a pervious stratum, 
such as a bed of loose sand, the ascending water is liable to pass into 
that stratum instead of returning to the surface. This quickly results 
in the clogging of the hole, and in order to prevent it the water which 
is pumped in is mixed with a large amount of fine clay. By this 
means the outlets through porous beds are sealed up, the unconsoli- 
dated material forming the walls of the hole is prevented from caving, 
and the water returns unimpeded to the surface. 
The forms of bits most commonly used are shown in PI. XI, A, B, C. 
The fish-tail bit (A) is adapted to soft materials, such as sand and 
clay. The core barrel bit (B) is better adapted for harder materials, 
such as very compact clay, indurated sand, etc. Where rock is 
encountered the ordinary bits make very slow progress, and the drill- 
ing is greatly facilitated by the use of the adamantine, or shot, drill, 
the cutting being done by a quantity of steel shot which revolve under 
the rim of the tube (C). Some drillers, in passing through hard 
rock, rig up a regular churn drill, the cable passing over a pulley at 
the top of the derrick and thence down to the engine fly wheel, where 
a turn around the crank pin gives the required lifting-and-dropping 
motion to the drill. 
When everything is ready to begin operations a length of rod with 
the bit attached is made fast to the water swivel and lifted into the 
derrick. The bit and lower end of the rod are passed through the 
rotary far enough to allow the jaws to be brought together and clamped 
so as to hold the drill rod and rotate it. The driller starts the engine 
and sets the pump in motion. As soon as the water flows freely he 
slackens the friction and allows the drill to descend. 
The force of water, which varies from 40 pounds to 75 or 80 pounds, 
passing through the rod finds its way as jets through two holes, one 
on either side of the fish-tail bit, and washes the freshly loosened sand 
up to the surface through the space between the drill rod- and the 
wall of the well. As the work progresses the driller lowers the rod 
slowly, holding it stationary or letting it descend, according to the 
character of the material through which the bit is working. From 
this time on the whole responsibility rests upon the judgment of the 
driller. The drilling crew generally consists of four men — the driller, 
