Now welding crews go to work fastening the ends of the pipe-lengths together. When they have finished, the “hot-dope gang” comes along. They are men who cover the pipe with a wrapping and then with a hot asphalt mixture to protect the metal. Meantime, a wonderful machine called a trencher has been at work. This is a cat attached to a rig which [Illustration] [Illustration] looks very much like an old-fashioned water wheel. Each bucket on the wheel has steel teeth. The cat turns the wheel and pulls it forward. The buckets scoop up earth, and spill it out onto a belt that dumps it in a heap at one side. The trencher plugs ahead, uphill and down, digging a ditch just the right width and depth. Following behind the trencher, cats with booms hoist up the snaky pipeline and ease it over into the trench. Finally, bulldozers backfill the trench. That is, they cover the pipe with the dirt that the trencher left alongside. On one job, the men had to work at top speed in the desert and in rocky, mountainous country. They were all so glad they’d finally succeeded in getting the pipeline built that they put on a celebration. Whooping and hollering, they tossed their sweat-stained hats into the trench in front of the bulldozer as it backfilled the last few feet of earth. [Illustration] Even after that there was one more tool that had work to do before oil could be pumped through their pipeline. It is a peculiar gadget that looks like a bunch of cowboy spurs hooked up with pieces of tin can and some old plates. The weird contraption is called the go-devil, and it has the job of traveling, perhaps hundreds of miles, inside the pipe, pushing out anything that could clog the line. Water pumped into the line behind the go-devil forces it through the pipe. In one line, the go-devil brought out chunks of wood, pieces of rock--and several rabbits, skunks and rattlesnakes that had decided the pipe would make good headquarters! Now the powerful pumps could go to work shoving oil through the line. MINING MACHINERY Oil pumps today are much better and stronger than the first pumps ever built, but they are direct descendants of the ones that were invented for use in English coal mines long ago. In fact, those early pumps were the great-granddaddies of all modern machines. [Illustration] [Illustration] Coal miners in England had dug so far beneath the surface of the earth that the shafts and tunnels were in danger of filling up with water. Neither manpower nor the power of horses hitched to pumps could do the tremendous job of keeping the mines dry. Something much stronger was needed. In order to find a new kind of power, inventors began experimenting with steam. The first workable steam engines were made to pump out coal mines more than two hundred years ago.