Box 4, Folder 3: Typewritten Letters 1866-1870

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The question is often asked whether the great fires of the north-west during the months of September, October, and November 1871 and especially the one which leveled to the ground a large share of the City of Chicago, had any decided effect upon the weather either by creating or modifying currents of air or by causing a fall of rain. It was reported by telegram to London, England, and there published "that this fire was chiefly checked on the third or fourth day by the heavy and continuous downpour of rain which it is conjectured was partly due to the great atmospheric disturbances which such an extensive fire would cause, especially when we are told that the season just previous to the outbreak of the fire had been particularly dry." This was said to afford an additional example from which to judge of the truth of the so-much-disputed assertion that extensive fires are almost invariably followed by heavy down-pours of rain which have been caused by them.

A very little attention to the facts exhibited by this great fire will show that no such "down-pours" occurred; and that the fire was checked; not by rain, but for want of other combustible material in the direction towards which the flames were driven by the winds.

The fire commenced at 9 1/2 P.M. of Sunday October 8th, and continued during that night and most of the succeeding day. By 2 A.M. of the 9th I had reached the Court House and the Sherman House and was consuming the most valuable portions of the city. Twelve hours later it was raving Lincoln Park in the north part of the city. The last house consumed (Dr. Foster's) was in flames before 10 P.M. Commencing at a point in the south west part of the city the fire moved rapidly to the north eastward and only ceased when it had reached the extreme north part of the city on the [shore...]

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[shore] of Lake Michigan on the east. After this time there was but little spread of the flames though the burning buildings were not yet entirely consumed.

During all this time, twenty four hours of continuous conflagration upon the largest scale, no rain was seen to fall nor did any rain fall until about 4 o' clock the next morning and this was not a very considerable "down-pour" but only a gentle rain that extended over a large district of country, differing in no respect from the usual rains. The quantity as reported by meteorological observers at various points was only a few hundredths of an inch. It was not until four days afterwards (14th) that anything like a heavy rain occurred.

It is therefore quite certain that this case can not be referred to as an example of the production of rain by a great fire.

Must we therefore conclude in his theory on that subject? By consulting his Reports (4th Report 1857 p. 29) it will be found that he only claimed that fires would produce rain under favorable circumstances of a high dew point and a calm atmosphere. Both these important considerations were wanting at Chicago where the air was almost destitute of moisture and the wind was blowing a gale. To produce rain the air must ascend until it becomes cool enough to condense the moisture, which then falls in the form of rain. But here the heated air would not ascend very far being forced off in nearly a horizontal direction by the great force of the wind.

The case therefore neither confirms nor disproves the Espian theory and we may still believe the well authenticated cases where, under favorable circumstances, of very moist air and ab

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sense of wind, rain has been produced by large fires.

At some other places where fires occurred of considerable extent, rain was observed to fall during their progress, but so far as is known these were general rains extending equally over the country and not produced by or apparently affected by the fires.

Had the great fires occurred during a calm, doubtless many of the phenomena described in Espy's theory--the ascending current, the in blowing air from all directions, the cloud formation above,--and possibly even rain might have been produced; but all this was prevented or very materially modified by the lack of moisture and the great force of the south-west gale.

The effect of these great fires upon the currents of air was also materially modified by the great force and velocity of the south-west gale. While it is undoubtedly true as stated by Espy and others that the increased temperature of the air causes it to rise and thus produce an inflow of the surrounding atmosphere from all sides, it is manifest that the great gale prevents an inflow from the front and increases it in the rear. Different observers represent the wind as sweeping along at a fearful rate, increasing as the fire progressed. While some report a whirling motion, others say the motion was direct. As the flames arose above the tops of the houses or of the forests they were forced forward by the fierce gale. Fire-brands were carried a great distance; and even roofs of houses are said to have been lifted up and precipitated upon adjoining buildings. It was at sometimes difficult for a strong man to resist the force of the wind.

The approach of the fire is represented as very rapid and accompanied by unusual sounds which increased to that of Niag

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-ara. Piles of lumber were blown away, chimneys thrown down and sand and ashes were swept along like drifting snow.

Under these conditions the fires of course spread with the most fearful rapidity in the direction towards which the wind was blowing, its velocity being such as to carry the hot air, the flames and the burning brands directly forward. The predominant force of the south-west wind was sufficient to over come any tendency towards local currents. But fluctuations in the direction of the wind always occur--and gave rise to different statements as to its direction. But there can be no reason for the blunder of an Illustrated N.Y. Weekly by which the flames are represented as being carried in a direction exactly contrary to the facts.

The draft of air upon the two sides of this rapidly progressing stream of fire, near the ground was often very considerable. The lateral spread of the flames was against this draft and of course was comparatively quite slow in its progress.

Masses of flames were blown forward and are described as balls of fire that were observed to fall like meteors in different parts of the town igniting whatever they came in contact with.

Another account says "that the fire came from the air above more than from the earth. It swept along in detached clouds borne with a tornado like fury. The clouds of fire, hot as a furnace blast would be swept along in "waving masses of different sizes." One man describes one of these clouds as of "forty feet in size each way. Whatever he saw it touch, the object, tree, or house wilted right down. These clouds of fire usually touched the tops of the tallest houses first, when the buildings would burn down

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just as if saturated with kerosene. It seemed as if the air was "Charged with fire."

The intense heat and great rapidity with which houses were consumed, are among the most wonderful facts connected with these fires, and have given occasion for the suggestion of several causes both natural and super-natural. It is believed however, that a slight consideration of the effects of the blow-pipe and of the blast furnaces will sufficiently explain all the observed facts. The strong wind constantly supplying oxygen to the flames increased their magnitude and the intensity of the heat.

The telegraph wires indicated no unusual disturbance of the electrical conditions of the atmosphere, and the rapid production of flame under the fierce blast of wind will account for the intensity of the heat without resorting to the theory of the decomposition of the atmospheric air.

We may therefore conclude that these fires were rendered possible and owe their intensity and magnitude to meteorological causes, "and that they neither confirm nor disprove Prof. Espy's theory of storms and the artificial production of rain.

Oct. 15. According to James McIntosh, U.S. Storm Signal Observer the wind blew at 9 to 11 P.M. the 8th, 12 to 16 miles S.S.W. per hour increasing to 30 by 12 o' clock and a furious gale before morning. The wind towards the fire in the streets.

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