Forget chainsaws - if you have to clear a jungle in a jiffy, reach for the 4-1/2 ton bowling ball. From a 1953 edition of Mechanics Today:
SCORES of times every day in an area near Hungry Horse, Montana, a man-made hurricane takes place. Hurtling through heavy timber with relentless force and a crash heard for miles, a giant steel ball, as big as a garage, snaps trees two feet thick as easily as if they were match sticks. Known as the “ball that saves millions,” this is a revolutionary method for clearing timber in record-breaking time and far cheaper on a large scale, than anything else ever known. The ball, weighing 4-1/2 tons, and measuring 8 feet in diameter, is pulled through the timber by two powerful diesel tractors traveling several hundred feet apart. Two, three and sometimes more trees are grabbed and “bitten” by a tenacious loop of cable. In a matter of seconds they are either uprooted or broken off. The ball rolls on a 6-inch shaft and in- I creases the efficiency of the snagging operation by keeping the cable approximately four feet off the ground, thereby preventing hangups on stumps and giving better leverage in pulling down trees.
One ball and a pair of tractors can clear about 50 acres per hour: Link