METHOD OF ESTIMATING INTENSITY
In a comparison of ionization theory with observation, some measure of line-intensity is required which can be compared from class to class. It seems probable that direct estimates of intensity, for spectra of the same dispersion, density, and definition, will be comparable within the limits of accuracy of the material.
Two series of spectra were measured by the writer in order to obtain material for the test of the theory of ionization. For the first group standard lines in the spectrum of
Cygni were used for the formation of a direct intensity scale, and for the second group, comprising the cooler stars, a strip of the solar spectrum was similarly employed. An arbitrary scale was constructed by assigning a series of intensities to well placed lines in the spectrum, and using these as standards. A list of the lines used for the second group, the assigned intensity, and the intensity as given in Rowland’s table, are contained in the following table.
| Line | Intensity | Line | Intensity | |||
|---|---|---|---|---|---|---|
| Assigned | Rowland | Assigned | Rowland | |||
| 4034 | 6 | 7 | 4046 | 10 | 30 | |
| 4035 | 5 | 6 | 3968 | 13 | 700 | |
| 4038 | 4 | 4 | 3934 | 15 | 1000 | |
| 4064 | 8 | 20 | ||||
The estimates thus made might be defined as estimates of width-intensity-contrast between the line and the continuous background. On an ideal plate which was not burned out, such estimates would give a measure of the total energy of the line relative to the neighboring continuous spectrum. The accuracy attained by direct estimates of this kind appears to be as great as the material warrants.
ACCURACY OF THE ESTIMATES
It is not possible at present to evaluate the accuracy of these estimates with the same precision as for other physical quantities, but the consistency of the readings from comparable plates of the same star will at least give a measure of the value of the estimates. [Table XVIII] contains the measures on forty-three lines in the spectrum of
