We reproduce below a somewhat revised table by Dr. Wegener of Marburg, who has made the most recent computation of the percentages of the various constituents of air at different heights. Consideration has been given to the fact that the composition of the air does not change except as regards the percentage of moisture within the troposphere, which is assumed to reach a height of 10 km. (6.2 miles). As usual in similar cases the percentages refer to volume. -------------+-----------------+----------+--------+---------- _Height_ | _Pressure_ | | | -----+-------+--------+--------+ | | _in | _in | _in | _in |_Hydrogen |_Helium |_Nitrogen km._| miles_| mm._ | inches_| 2_ | 4_ | 28_ -----+-------+--------+--------+----------+--------+---------- 0 | 0 |760 |29.9 | 0.0033 | 0.0005 | 78.1 -----+-------+--------+--------+----------+--------+---------- 10 | 6.2 |197 | 7.75 | 0.0033 | 0.0005 | 78.1 -----+-------+--------+--------+----------+--------+---------- 30 | 18.6 | 8.95 | .352 | ---- | ---- | 85 -----+-------+--------+--------+----------+--------+---------- 50 | 31.0 | 0.45 | .0177 | 1 | ---- | 88 -----+-------+--------+--------+----------+--------+---------- 70 | 43.5 | 0.045 | .00177| 13 | 1 | 80 -----+-------+--------+--------+----------+--------+---------- 90 | 55.8 | 0.0157| .00062| 68 | 5 | 26 -----+-------+--------+--------+----------+--------+---------- 110 | 68.2 | 0.0116| .00046| 94 | 5 | 1 -----+-------+--------+--------+----------+--------+---------- 130 | 80.6 | 0.0097| .00038| 96 | 4 | 0 -----+-------+--------+--------+----------+--------+---------- 210 | 130.2 | 0.0055| .00022| 99 | 1 | ---- -----+-------+--------+--------+----------+--------+---------- 310 | 192.6 | 0.0032| .00013| 100 | ---- | ---- -----+-------+--------+--------+----------+--------+---------- 410 | 254.2 | 0.0021| .00008| 100 | ---- | ---- -----+-------+--------+--------+----------+--------+---------- 510 | 316.2 | 0.0016| .00006| 100 | ---- | ---- -----+-------+--------+--------+----------+--------+----------