Paris Smalls, founder of Eden GeoPower, breaks subterranean rocks with electricity. His precision fracturing technique could be used to stimulate hydrogen production. In a tranquil Boston suburb , on the far edge of a horse farm, where pasture gives way to woods, a crane lowers an enormous electrode into a borehole. The electrode, a half-meter-long cylinder with copper-tipped arms to ensure good contact with the borehole walls, descends—deeper, deeper—through layers of spongy sandstone to the hard, marbled roots of an ancient mountain range hundreds of meters below ground. Here the rock is tight; there are few cracks for water or gases to flow. But that’s about to change. A stone’s throw away, a second electrode—a twin of the first—has been fixed in another borehole at the same depth. From above ground, a pair of high-voltage generators cabled to the two electrodes fires a series of pulses. Tsss!…Tsss!…Tsss!…Tsss!…Tsss!….…