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SCIENTIFIC STOOL PIGEONS                            6

the information gained from the underground survey.  But because of the survey, we were able to locate the oil bearing structure very accurately.  This enabled us to make perfect water shutoffs which saved us and the other operators in the field millions of dollars because of immediate completion of wells instead of many recementing and fishing jobs."

Nearly all wells pass through water bearing formations on their way to the pay sand.  Before the well is brought in, this water must be sealed out by cementing the space between the casing and the wall of the hole.  Failure to make this water shut off perfectly has made paupers of many oil operators and has ruined many promising oil fields by letting salt water into the oil sand.  To determine the exact point where salt water enters the hold was impossible until the recent invention of the "water witch", another underground tattle-tale.  It is an electric instrument that depends on the change in resistance of the fluid in the hole because of the presence of salt water.

The mud weight indicator tells the driller the condition of the fluid circulating in his well.  If gas is encountered, the dial warns the driller in time for him to take steps to prevent a dangerous and costly blow out.

The steam flow indicator or, in the case of electrically driven rigs, the recording watt meter, tells the driller the amount of power the bit is requiring to do its work.  This gives him a good indication of whether the formation he is drilling is hard and brittle or soft and sticky; whether he should feed the bit down fast or slow; wheter he should use more or less weight.

Many of these new instruments find application in other fields than oil well drilling.  In sinking shafts for coal mines in England, Belgium,