They all carefully observed the register and then proceeded with their mentor down the hill a little way. He there exhibited his instrument again and it registered fifty feet lower than it had done on the plateau above. Returning to the camp fire they found that the needle had resumed its former pointing.
"Then you can tell by that instrument exactly how high you are at any time?" queried Jack.
"No, not exactly. You see the atmospheric pressure varies somewhat with the weather even if you observe it always on the same level. One has to allow for that, but allowing for it we can tell by the instrument what our elevation is with something closely approaching accuracy."
Just then came an interruption. A tall rough bearded, unkempt mountaineer, rifle in hand, stalked out of the woods and approached the camp fire. After inspecting the company and their belongings in silence for a time, he spoke a single word of question—"Huntin'?"
"No," answered Jack, who had risen in all his length of limb.
"Trappin'?"
"No."
"Jest campin' out?"
"No," answered Jack, still adhering to that monosyllable.
"Mout I ax then, what ye're a doin' of up here in the high mountings? You see us fellers what lives up here ain't over fond of strangers that comes potterin' round without explainin' of their selves."