THE measurement of the wave-lengths of the dark lines of the solar spectrum obtained by photographs, and the construction of a chart of the same, has for many years occupied my leisure time. As a ...

Experiments lead to a greater understanding, deeper insights, and sometimes they even bear fruit. That was certainly the case ...

The writer has frequently sea one bright line in the yellow, near D (coincident with on,e of a group of lines which appear in the solar spectrum, when the sun is near the horizon), and one faint ...