Liquid Oxygen Questions

First, if we assume an atmospheric pressure, could be anything, but
let's work with 1 atmosphere. The effect of this atmospheric
pressure would be to exert a force of 15 lbs/in2 against the
pressure vessel. O'Neill assumed an atmosphere of 1/2 sea-level pressure, with the percentage of oxygen doubled, and the percentage of nitrogen reduced accordingly. Mostly to reduce that pressure load, which would be the lion's share of the total loading, even assuming rotation for 1 G. Now how does the radius of the cylinderical habitat
effect the total mass of the atmospheric gases? The way I see it,
the mass of the gases is directly proportional to the area of the
pressure vessel and the height has no effect. Not at the kind of scales we can realistically talk about within the limits of current material strengths. Air mass would roughly vary with the cubic volume, as the pressure at the spin axis would be scarcely any less than at the cylinder floor. O'Neill cited as one of the advantages of Island 3 that mountain climbers and glider pilots would find they had no breathing difficulties no matter how "high" they went, at altitudes where here on Earth breathing apparatus is called for. But there was one guy who wrote a paper on the subject of how diamondoid (would require molecular-scale manufacturing) could affect the space picture. In addition to Super-Shuttles and orbital elevators, he also talked about mega-cylinders. These would be so huge (1/13th the diameter of the Earth if Ifigured correctly) that the atmosphere would pool on the cylinder floor, and one would have the situation that I suspect you've been visualizing. On commenting that one wouldn't be able to strap on wings and fly near the axis as had been advertised, he then scaled down his design so that the pressure at the axis would be at least half of what you saw on the cylinder floor. Of all the possibly sensible reasons one might have for scaling the cylinder down, I wouldn't let that be one. One might imagine large pressurized spheres up near the axis for flying in equipped with air compressors.