coincide with theory, then our descent will be arrested at no great depth."
"And," I said, "unless the discrepancy between fact and theory is a remarkable one, we will have no means of knowing whether the law has broken down or not."
"We shall have no means of knowing, Bill—unless, as you say, truth and theory are remarkably divergent. Of course, in that case, we should not long remain unaware of the fact. Of the depth, then, we can not be certain; but the boiling point will always give us the atmospheric pressure."
"That isn't what is worrying me," I told him; "it is the pressure itself."
"The pressure itself," Milton returned, "would produce no dire effects. It is not the diminution of pressure that produces the dreaded mountain sickness, as was clearly shown by Dr. Paul Bert. Of educated people, nine hundred and ninety-nine out of every thousand will tell you that the acceleration of the pulse as one ascends to lofty heights, the short, troubled breathing, the disordered vision, extreme weakness, nausea, vertigo, bleeding at nose and lungs, in short, all the symptoms of the terrible mal des montagnes, are caused by the diminution of the atmospheric pressure. The average human being—such is their explanation—having a surface of about fifteen square feet, sustains an atmospheric pressure of more than thirty thousand pounds; at an elevation of eighteen thousand feet, the pressure is but one-half of that; is it any wonder, then, that a man gets mountain sickness?"
"Shades of ten thousand Gullivers," I exclaimed, "do you mean to say that those nine hundred and ninety-nine are wrong?"
"Certainly they are wrong, so wrong as to cause Dr. Bert to write:
'It is amazing to find a theory so plainly at variance with elementary physical laws accepted by eminent men.'"
"Well, well," was my sage remark, "I suppose the next thing on the program will be the statement that it is not the fire that makes the pot boil; it is the heat."
"If it doesn't rain, Bill, tomorrow will be Monday. However, Dr. Bert (Professor in the Paris Faculty of Sciences) proved 'that the lessening of the barometric pressure,' to use his own words, 'is of no account, mechanically, in the production of the phenomena.' Yes, he proved that, to use his own words again, 'it is not the lowering of mechanical pressure that produces the symptoms, but the low tension of the oxygen of the dilated air, which low tension prevents the oxygen from entering the blood in sufficient quantity.' Dr. Bert not only experimented on sparrows but entered the air-chamber himself. As the pressure was reduced, he experienced all the symptoms of mountain sickness. 'But,' he says, 'all these symptoms disappeared as by enchantment as soon as I respired some of the oxygen in the bag; returning, however, when I again breathed the air of the cylinder.'
"In one of his experiments, the pressure was reduced to 246 millimeters—9.7 inches. 'This,' he says, 'is exactly the pressure on the highest summit of the Himalayas—the same degree of pressure which was so near proving fatal to Glaisher and Coxwell; I reached this point without the slightest sense of discomfort, or, to speak more accurately, the unpleasant sensations I felt at the beginning had entirely disappeared. A bird in the cylinder with me was leaning on one side, and vary sick. It was my wish to continue the experiment till the bird died, but the steam-pump, conspiring, as I suspect, with
