Science (journal)/Volume 5/No. 120/The Ruddy Glow around the Sun

by G. H. Stone

The ruddy glow around the sun.

In November, 1883, at the time of the remarkable after-glows, I noticed that there was a broad, reddish ring around the sun even at mid-day. Soon after, I briefly described the appearances in Nature. Since then, I have constantly observed this phenomenon. The sky is very bright for about ten degrees from the sun; then comes the ruddy zone about twenty degrees wide, the deepest color being at about the natural distance of halos. My observations show that at this place there are but few days of the year when the chromatic glow is not visible; but it varies in intensity not only from day to day, but even from hour to hour. About a year ago I discovered that an increase in the depth of color preceded a fall in the temperature, and the formation, first of a structureless haze in the upper atmosphere, and, soon after, of cirrhus-clouds. At other times storms came on with no increase in the depth of color. Soon it became evident that the latter cases were when rain fell, and the general temperature was not low. Hail and sometimes snow storms were accompanied by great depth of color. During the summer of 1884, I passed several weeks in Maine. On two occasions the colored zone appeared around the sun as distinctly as it ordinarily does here. Both times the appearance of the glow was followed by violent thunder-storms, with high winds and hail.

While temperature would not affect the diffractive power of particles of volcanic dust directly, yet it is possible that at a low temperature the dust particles, on account of the condensation of the air, may be enough nearer to each other to give a perceptibly greater diffractive power to the mass of air in which they are suspended. But so often has an increase in the depth of the circumsolar glow preceded the formation of clouds, that it seems far more probable that the glow is caused by the precipitation of atmospheric moisture at low temperatures. If dust is involved in the process, it is probably only by its increasing the depth of color, or by its facilitating the precipitation of moisture.

In substance, these views have been expressed verbally to numerous persons for more than a year past. They are published now not merely as a matter of theoretical meteorology, but also for a practical purpose. The observations here recorded make it probable that the glow may be utilized as a prognostication of hail. It goes without saying, that it will be of great value to many, especially tn those who have much exposed glass on the roofs of greenhouses, etc., to be able to predict hail and a fall in the temperature. It is true that other localities than those named may not show the same phenomena. The subject is worthy of the careful study of the signal-service, and of meteorologists generally.

G. H. Stone