+---------+----------+----------+----------+----------+----------+ | X Volts | Pressure | Pressure | Pressure | Pressure | Pressure | | per cm. | .17 mm. | .38 mm. | 1.10 mm. | 2.1 mm. | 4.1 mm. | +---------+----------+----------+----------+----------+----------+ | 20 | .24 | | | | | | 40 | .65 | .34 | | | | | 80 | 1.35 | 1.3 | .45 | .13 | | | 120 | 1.8 | 2.0 | 1.1 | .42 | .13 | | 160 | 2.1 | 2.8 | 2.0 | .9 | .28 | | 200 | | 3.4 | 2.8 | 1.6 | .5 | | 240 | 2.45 | 3.8 | 4.0 | 2.35 | .99 | | 320 | 2.7 | 4.5 | 5.5 | 4.0 | 2.1 | | 400 | | 5.0 | 6.8 | 6.0 | 3.6 | | 480 | 3.15 | 5.4 | 8.0 | 7.8 | 5.3 | | 560 | | 5.8 | 9.3 | 9.4 | 7.1 | | 640 | 3.25 | 6.2 | 10.6 | 10.8 | 8.9 | +---------+----------+----------+----------+----------+----------+ We see from this table that for a given value of X, [alpha] for small pressures increases as the pressure increases; it attains a maximum at a particular pressure, and then diminishes as the pressure increases. The increase in the pressure increases the number of collisions, but diminishes the energy acquired by the corpuscle in the electric field, and thus diminishes the change of any one collision resulting in ionization. If we suppose the field is so strong that at some particular pressure the energy acquired by the corpuscle is well above the value required to ionize at each collision, then it is evident that increasing the number of collisions will increase the amount of ionization, and therefore [alpha], and [alpha] cannot begin to diminish until the pressure has increased to such an extent that the mean free path of a corpuscle is so small that the energy acquired by the corpuscle from the electric field falls below the value when each collision results in ionization.