John Wolcott Phelps, Connecticut River Fog

The Fogs Of The Connecticut River.

Fog is a cloud which forms near the surface of the earth. The reason of its formation at various times and localities is not fully understood, yet enough is known to lead one to infer that the electrical condition of the air has more or less to do with it. Indeed, very large sparks of electricity have been drawn from fog through the means of insulated wire.

But we propose, in the present paper, to limit our remarks to the fogs which at certain seasons of the year occur along the Connecticut River, and we shall confine our observations to such traits of their character as may be ascertained by the eye aided only by the thermometer. For this purpose, we give the following table of some of the fogs that were noticed in the fall of the year 1864.


On the 21st of September the thermometer in the air stood at 49 degrees, and in the river at 63 degrees. The apparent condition of the atmosphere and the aspect of the sky were the same as the day preceding, with this difference, that on the 20th there was a gentle flow of the air from down the river, while on the 21st the flow of the air was from the westward and yet there was no fog. But on the night intervening between the two days however, there was a display of the Northern Lights.

On the 17th of September, the fog was very heavy. It extended back some distance from the river, and was so dense that the roads were moistened with it, and the roofs of houses became dripping wet. And so on the following day, the 18th of September, a dense fog extended back a mile and a half from the river. The inside of the window panes, on the mornings of both of these days, was thickly covered with beads of moisture, the warm vapors of the room becoming condensed upon the cold glass in the same manner that the vapors of the outside air became condensed by a considerable fall of temperature. On the night of the 16th, there seemed to be every sign of a frost; and in fact garden plants and the tobacco crop would probably have been nipped, if it had not been for the intervention of the fog: for by the condensation of the moisture into fog, latent caloric is given out, which warms up the air and prevents a frost. And this is a beautiful provision of nature by which a source of danger is converted into one of safety. In the vallies and low lands, where the night air is still and hence favorable to the congelation of water, the condition of the air is less favorable to the formation of fogs, while on the hill sides, where the breezes freely play, frost cannot take so readily, and vapors are diffused instead of being condensed, so that fogs are not readily formed.

That the water of the Connecticut River, and the fogs which arise from it, warm up the land immediately along its course, beyond what it would be warmed without such a cause, will appear pretty evident by an inspection of the table.---From the 11th of September when the temperature of the air was nearly that of summer heat, until the 16th of December when the earth was covered by nearly a foot's depth of snow, and the river was bordered with ice, the range of the thermometer was on an average more than ten degrees higher when immersed in the river than when exposed to the air. And this view of the effect of the river in warming up the land in its vicinity, in Vermont, would seem to be confirmed by the fact that the chestnut tree, which requires a moderate climate, does not extend far inland from its banks.

Another fact, we may mention in passing, is discovered by an inspection of the table. From the 11th to the 17th of September, it will be observed, there was a sudden change of temperature of eleven degrees. This change takes place pretty regularly throughout the United States, every year near the middle of the month of September, or about the period of the autumnal equinox; and as it is unexpected and unprovided for, it usually occasions a good deal of sickness. A sudden change from a long spell of summer heat to a temperature near the freezing pint cannot be otherwise than deleterious to the health, and can be safely met only by having warm clothing ready to be put on the moment that it begins to take place.

As a general rule, the fogs over the Connecticut River are produced in the following way. During the night, when they are formed, the air in the deep valley is still moist and warm, and a cool dry breeze from the westward---from the mountains---flows over it. The moment that this cold air strikes the warm air over the river, the moisture of warmer air becomes condensed and forms a fog. But as the cool air is also dry, the moment that the vapor has become condensed by its coolness that same moment it begins to be absorbed by its dryness, so that the fog while forming from below, is at the same time being absorbed into invisible vapor above. Thus, under the two opposite actions of consensation and absorption, the fog remains stationary, and fills the whole valley of the river with a compact, distinctly outlined mass, winding along among the hills like an immense river itself. From the hill tops one looks down upon it, shining white with the morning sun, and stretching off towards the distant sea. As the sun rises higher, and the air becomes warmer and hence more capable of absorbing and containing moisture, the fog begins to be diminished, until finally it suddenly vanishes from view.

J. W. P.

Vermont Record, February 21, 1865.


Temperature Calculations

Diary By John W. Phelps

July 1, 1860 -- April 2, 1865

In this Diary on January 23, 1862---

During the fog sounds
were heard more distinctly than
usual, showing that the currents
were downward.

On June 19, 1864---

Many farmers are raising tobacco, the stoppage of the supply from the south rendering it profitable - But owing to the present dryness, they are disappointed in not being able to set out their plants without great additional labor.

On July 17, 1864---

A number of trees were prostrated by the storm in the vicinity of Algiers. An old chesnut tree which I knew when a boy, and which has always yielded chesnuts, I believe, every year, situated on a ledge of rock directly west of the house, was prostrated. With its huge mass of roots turned up it looked a sad view to me, as if boding no good. In the midst of its bloom it has stretched down the hill towards the S. E., a wreck amidst many memories of the past that hover around it, never to be awakened by its old branches, by its sunny, benevolent fruit again.


Diary Sketch Following February 27, 1861 Aurora Borealis


This paper does not describe the military significance of early morning fog in delaying the onset of battles, but Gen. Phelps was clearly aware of the importance for learning more about this phenomenon. During the Civil War, antagonists could not resort to radar.

The Diary of John Wolcott Phelps is a trove of information concerning meteors, Zodiacal Lights, auroras, storms, flood, tornado, bobolink, whippoorwill, bluebird, and come May, the inscrutable formations of tadpoles. The man's sense for the connectedness of things is everywhere, overwhelmingly in evidence.

This entry shows his efforts to determine the aurora borealis altitude---


Calculations To Determine The Altitude Of The Northern Lights Above The Horizon




Site Design © Vermont Technology Partners, Inc.