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6

SCIENTIFIC STOOL PIGEONS

the information gained from the underground survey.  But because of the survey, we were able to locate the oil bearing structure very accurately. ^[[circled X in right margin]] This enabled us to make perfect water shutoffs which saved us and the other operators in the field million s of dollars because of immediate complotion 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, thin water must be sealed out by cementing ^[[3 the]] [[strikethrough] the [[/strikethrough]] 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 hole was impossible until recent invention of the "^[[underlined]] water witch [[/underlined]]", another underground [[strikethrough]] tattle-tale [[/strikethrough]]. ^[[sorcerer.]] It is an electric instrument that [[strikethrough]] depends on [[/strikethrough]] ^[[registers]] the change in resistance of the fluid in the hole [[strikethrough]] because of the presence of [[/strikethrough]] ^[[when it enters a zone filled with]] salt water.

The mud weight indicator tells the driller the condition of the fluid circulating 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. ^[[paragraph circled, 4 in right margin]]

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; whether 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, ^[[mark through last paragraph, circled 5 in right margin]]