The general conclusion would appear to be that, while as seen from the earth's surface much of the light from the sky is due to comparatively gross suspended matter, yet an appreciable proportion is attributable to the molecules of air themselves, and that at high elevations where the blue is purer, the latter part may become predominant.
In winter the varying depth of snow may exert an appreciable effect.
It is thus customary in calculating diurnal inequalities either to take no account of days on which there is an appreciable rainfall, or else to form separate tables for " dry " or " fine " days and for " all " days.
In two cases, however, it has been found in the absence of appreciable quantities of uranium and thorium compounds, namely in beryl, and in sylvine (potassium chloride).
The growth of a wider patriotic sentiment must depend on the spread of popular education; certainly up to 1908 no appreciable progress had been made in this direction.