The first 5 journals were observations, 31 years of observations. He had measured the temperature inside the cave every morning and every evening, at the mouth and at 50 feet and at 100 feet. He had recorded the outside temperature at the same times. He had noted the wind direction, the humidity, the phase of the moon. He had burned smoke pots at the cave mouth and watched which way the smoke went. And he had discovered something that nobody else in Monroe County knew.
In summer, cool air flowed out of the cave during the day because the deep rock stayed cooler than the outside air. In winter, warmer air flowed out at night because the deep rock stayed warmer than the outside air. The cave breathed. It really breathed, just as the children said. But it was not breathing because it was alive. It was breathing because of physics. I did not know the word physics then. Silas did not use it either. He wrote about the mountain’s steadiness and the stone’s memory of other seasons. But what he meant was that deep in the limestone, past the first chamber and into the passages beyond, the rock held a temperature close to the yearly average. Summer did not heat it much. Winter did not cool it much. It just stayed 52, 53, 54 degrees, year after year after year.
And Silas had wondered: what if you could borrow that steadiness?
Journals 6 through 9 were maps, hand-drawn cross-sections of the cave with arrows showing airflow and numbers showing temperatures at different depths, smoke-test results, diagrams of how the cave connected to the outside through cracks he had found in the bluff face. Journals 10 through 12 were construction plans.
Silas had designed something he called a winter throat: an enclosed passage from the cabin to the cave mouth, sealed tight with doors at both ends and a baffle vent in between. The idea was simple but strange. Instead of trying to heat the cabin with fire alone, he wanted to connect the cabin’s air to the cave’s air, let the mountain’s steadiness buffer the cabin against the killing cold of February, let the stone do some of the work that wood and fire usually did alone.
