dust into the air that the trail, which girdled the earth several times, was visible at sunset for nearly two years. The blood-red sky[1] at times rivaled the northern lights. Less marked red sunsets followed the eruptions of La Soufrière and Mont Pelếe in 1902. The explosion of a great quantity of munitions in New York Harbor was followed for several days by red sunsets observable as far west as the Weather Bureau station at Ithaca, N. Y. The dust mantle of the Greenland glacier is apparently of volcanic origin. Indeed, volcanic dust is always an important constituent of the floating dust of the air; at times it is the chief constituent.
The floating dust of the air has a marked effect upon its temperature. Benjamin Franklin noted this fact. During several months in 1783, the air was filled with floating volcanic dust. “The sun’s rays were indeed rendered so faint in passing through it that, when collected in the focus of a burning glass, they would scarcely kindle brown paper.” The heating power of the sun was so feeble that freezing temperatures began nearly a month before their normal occurrence. “Delaware River was closed in November and remained ice-bound until late in March.”[2]
The years 1812-1816 were years of great volcanic activity, and the air was loaded with floating dust. As a result, the year 18 16 has gone into history as the “year without any summer”—the year of “eighteen hundred and froze-to-death.” In Vermont snow fell and frosts occurred every month of that year. On the 8th of June, snow on the uplands was 5 or 6 inches deep.[3]
Humphreys has shown that, with a blanket of volcanic- ↑ By reflected light, fine dust particles tend to a whitish color, and to a bluish tint if very fine and fewer in number. The purity of the tint depends, to a certain degree, on the size of the particles. By transmitted light, especially when the sun is near the horizon, the blue and the violet rays are absorbed and scattered and the red rays reach the eye of the observer. When the air is full of floating dust, the scattering of blue and violet rays is very great.
- ↑ The Philadelphia Inquirer.
- ↑ Thompson’s History of Vermont.
days, during which time the coarser dust fell on the nearby islands and into the sea. This, a normal eruption, was separate and distinct from the explosion which shattered the island.
