stands always at a uniform temperature no matter whether it is boiling hard as we say, or only just barely boiling. But in a dense atmosphere it requires more heat to boil water than it does in a rarefied atmosphere like that up here on the mountain. At Leadville and other places lying from 10,000 to 14,000 feet above sea level in the Rocky mountains you can't boil potatoes at all and it takes full ten minutes to boil an egg into that condition which we call 'soft.' It all depends upon the temperature of boiling water, and that is considerably lower here than down in the valleys where we live."
"But Doctor," said Harry, "you promised to tell us how you find out how high we are above the sea level."
The Doctor got up, went to a tree and took down a scientific instrument.
"This," he said, "is an aneroid barometer. It measures the atmospheric pressure, and as that pressure steadily and pretty uniformly decreases as we go higher up, the instrument tells us at once how high we are."
"But will it measure so accurately that you can trust it?" asked one of the now eagerly interested boys.
"Let me show you," said the Doctor. "Make a torch, for it is growing dark, and come with me down the hill a little way. First look where the needle stands now."
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."
"Well" said Jack, "I don't see why I shouldn't tell you what brings us here. My mother owns a tract of timber land a little further around the mountain, and it is pretty much all she does own in the world. She's a widow, and she's had a pretty hard time to bring up three boys of us" – turning and indicating his two brothers – "and now we see a way of helping her. They're going to build a railroad down in the valley on the other side of this mountain, and they want railroad ties. So we have organized a party and come up here to chop down trees, make ties and send them down the mountain by a chute."
"Um," answered the mountaineer. "What's them there things for?" pointing to the Doctor's scientific instruments hanging about on the trees.
"They are scientific instruments, if you know what that means," answered Jack, who was beginning to grow irritable under the intruder's impertinent questioning.
"What are you goin' to do with 'em? Will they help you to chop wood?"
"No, of course not. But the Doctor here," indicating him, "is much interested in science and he has brought his instruments along so as to make our stay on the mountains as profitable as possible in the way of study."
"My friend," broke in the Doctor, addressing the mountaineer, "If you will come to our camp when we get settled I'll show you how I use these things and what they tell me. One of them tells me how high up we are and when it's going to storm or clear away; another shows how fast the wind is blowing, another how cold it is and so on."
"Which one on 'em tells the strength of whiskey and how much tax they ought to be paid on it?"
This question was asked with a peculiar tone of sneering incredulity and suspicion.
"Not one of them has any relation whatever to whiskey or taxes or anything of the sort," answered the Doctor.
By this time Jack's patience was exhausted and by common consent Jack was the leader of the party. He turned to the tree behind him, seized his shot gun, presented it at the mountaineer's breast before that worthy could bring his rifle to his shoulder, and in an angry, but still cold voice, said:
"I'll trouble you to lay down that rifle."
The man obeyed.
"Now I'll trouble you, if you please to lay down your powder horn and your bullet pouch and your cap box and everything else that pertains to that rifle." All this while Jack was holding the muzzle of his full-cocked, double barrelled shot gun in front of the man's breast, while all the other boys had seized their guns and stood ready for action. The Doctor had not a shot gun, but a repeating, magazine rifle of the latest make, long in its range, exceedingly accurate in its fire and equipped with fourteen cartridges in its magazine that could be fired as fast as their owner pleased. And the moment that the mountaineer, before he laid down his rifle, made a motion as if to bring it to his shoulder, the Doctor had stepped to Jack's side with his destructive weapon in position for instant use. After the man had laid down his arms, the Doctor stepped back, lowered his weapon and said to Jack: – "Manage the affair in your own way. Only be prudent, and above all don't lose your temper."
Jack then said to the mountaineer:
"You've asked us a number of questions. Now I want to ask you some. What do you mean by intruding upon our camp? Who are you? What right have you to ask us about ourselves and our mission in these mountains? Answer man, and answer quick or I'll put two charges of buck shot through you in less than half a minute."
"Now, don't be too hard on a feller, pard," answered the man. "I didn't mean no harm in partic'lar. But you see us fellers that lives up here in the high mountings has a hard enough time to git a livin' and we don't like to be interfered with by no revenue officers and no spies and no speculators from down below. You see if we're caught, some of the money goes to the informer, an' so we takes good keer to have no informers about, an' if they insist on stayin' we usually buries 'em. Now you've got the drap on me an' my only chance is to go way if you'll let me go. So far as I'm concerned you're welcome to go round the mounting an' chop all the railroad ties an' cordwood you choose. But there's fellers in the mountings that you ain't got no drap on, as you've got it on me, an' fellers what ain't so tender hearted as me. An' so, while I'll leave my gun an' promise never to meddle with you again if you won't shoot, at the same time my earnest, friendly, fatherly advice to you boys is to take yourselves down out'n this mounting jes' as quick as you kin. It ain't no place for people of your sort."
"We'll do nothing of the kind," answered Jack. "We've come up here on a perfectly honest and legitimate mission, and we're going to carry it out. We are not interfering with anybody and I give you warning that if anybody interferes with us it will be the worse for him. We are armed, every man of us and we are prepared to use our arms. Tom," – turning to his brother, – "take that man's rifle and discharge it into the cliff back there."
Tom obeyed the command instantly. Then Jack said to their unwelcome visitor, "Now you can take your rifle and go away. But don't intrude
