extends almost to 200 millimeters. The corresponding line is shown to be a close double.

The curve corresponding to the violet light of cadmium is shown in Fig. 68, and is seen to be comparatively simple.FIG. 67

We have thus shown that spectral lines are complex distributions of light, whose resolution in general is beyond the power of the spectroscope. This complexity of the spectral lines is particularly interesting because it indicates corresponding complexity of the molecules which cause the vibrations which give rise to the corresponding spectral lines.FIG. 68 This complexity may be likened to the complexity of a solar system; and while this may bring dismay to the Keplers and Newtons who may hope to unravel the mysteries of this pigmy world, it certainly increases the interest in the problem.