In arctic and subarctic landscapes, the frost line is the lower limit of permanently frozen ground (permafrost). In places such as Barrow, an Iñupiaq Eskimo village on Alaska’s Arctic coast, the frost line is more than a thousand feet deep. On a fool’s errand in 1881, Lt. Henry Ray, the leader of the ﬁrst Arctic science station in Barrow, supervised the digging of a pit to measure temperatures of frozen ground. Of this experiment, Charles Wohlforth writes: “According to local legend, he wanted to ﬁnd the bottom of the permafrost.” Weeks of digging produced a pit over thirty-seven feet deep. “We have no record of what the Natives thought of this activity,” Wohlforth writes, “but practically enough, an Iñupiaq family appropriated the hole as a prodigious ice cellar.” It was used to preserve whale meat for over one hundred years. In temperate climates, frost line has a different meaning, and is as important to farmers as tides are to mariners, as it indicates the maximum depth that ground freezes in winter. Those who have crops at stake speak of the frost line of a particular winter, of a series of winters, of the most extreme depth ever recorded. Even warm, mountainous places such as the Hawaiian Islands have their frost lines: altitudes below which freezing doesn’t occur.