“Yes, sir ... Mr.—Don, I mean.” Sandy felt a warm glow at this mark of friendship.
“One method of making an aerial survey is by means of photographs taken from a plane or helicopter,” the geologist explained. “A stereoscopic color camera is used to provide a true three-dimensional picture of the area in which you are interested. Such photographs show the pitch and strike of surface rock strata and give you some idea of what formations lie beneath them. In addition, prospectors use an airborne magnetometer. You know what a magnetometer is, don’t you?”
“It measures small differences in the earth’s magnetic field.”
“Right! I see that you listened when your dad talked about geology. Well, you fly a magnetometer back and forth in a checkerboard pattern over any area where photographs have shown rock formations favorable for oil deposits. Heavy basement strata are more magnetic than the sedimentary rocks that cover them. So, when those igneous basement rocks bulge toward the surface of the earth, your magnetometer reading goes up. That gives you a double check because, if the basement bulges, the sedimentary rocks that may contain oil have to bulge too. And such a bulge, or anticline, may trap that oil in big enough quantities to make it worth your while to drill for it.
“Then, if your money holds out—aerial surveys cost a young fortune—you may run a triple check with a scintillation counter to see whether there’s a radiation halo around the anticline. One complication with that is that you have to remove the radium dials from the instrument panel of your plane to keep leakage from interfering with your scintillation readings.”
A loud honking from the rear of the column caused Donovan to stop the jeep. Going back, they found that the new drill truck had slipped into a ditch and was teetering dangerously.
Although they had been traveling through such wild and arid country that it seemed impossible that even prairie dogs could live there, quite a crowd collected while they struggled and sweated for half an hour to get the machine back on what passed for a road. First came a wagon pulled by two scrawny horses and carrying a whole Navajo family—father, mother, two children and a goat. An ancient truck with three more Indians aboard pulled up in a cloud of dust. Then came two Navajos on horseback.
Ralph recognized one of the riders and gravely offered him a cigarette which he held crosswise between his first and second fingers.
“Hosteen Buray, we need your help,” said the driller after his gift had been accepted.
The rider said a few words to the other bystanders and things began to happen. The riders galloped away and came back dragging a small tree trunk that could be used to raise the truck axle. The children gathered sagebrush to stuff under the wheels. The woman milked her goat into a pan and presented the steaming drink to the thirsty oilmen. Finally, everyone got behind the machine and pushed with many shouts and grunts.