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Frémont's Meteorological Contributions
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Copyright ©2001 by Bob Graham

The elevated and arid plains of North America, similar to the steppes, has become known only since the surveys of Frémont at the time of his first completion of the circuit which defined it and proved its existence. Lorin Blodget, Climatology of the United States and the Temperate Latitudes of the North American Continent, 1857.

At the age of 24, Frémont applied for, and was appointed, a civil engineer in the newly organized Army Topographical Corps of Engineers by President Jackson. A number of government and railroad surveys followed. In 1838 Frémont was commissioned as Second Lieutenant of Topographical Engineers, and was assigned as chief assistant to a survey of the area between the upper Missouri and Mississippi Rivers.

Leading the expedition was fifty-two year old Legend of Honor member Joseph Nicolas Nicollet, an eminent French astronomer and mathematician, and foremost surveyor and mapmaker of his day. Nicollet, had been the protoge of Laplace, and is recognized in the last vol. of Mecanique Celeste as an observer of comets, and for his work on the great map of France. At the time of the revolution of 1830, Nicollet was astronomer at the Bureau of Longitudes at the Royal Observatory in Paris. Financially ruined by the revolution, he came to America, where he became associated with Rudolf Hassler of the U. S. Coast Survey.

This was a stroke of luck! With Frémont's background in mathematics, astronomy, and the physical sciences, Nicollet trained him in surveying, botanical, meteorological, and geological observation, and topographical map work.

In 1839, J. R. Poinsett, then Secretary of the Department of War, requested of Nicollet that he write an essay on Meteorological Observations. The essay was published by the Corps of Topographical Engineers. It is primarily a collection of questions and suggestions of topics to be studied.

If Nicollet's 1839 Essay on Meteorological Observations is considered seminal, Frémont's 1848 Geographical Memoir Upon Upper California, which accompanied the government publication of the 1848 Frémont/Preuss map of Upper California and Oregon, must be, in some regard, not just seminal, or contributory, or pioneering, but definitive.

On pp 6-7 of the 1848 Geographical Memoir is an entirely current description on the meteorological dynamics of the western states.

"It [Sierra Nevada] is a grand feature of California, and a dominating one, and must be well understood before the structure of the country and the character of its different divisions can be comprehended.

"It divides California [here pre state boundary, which includes the Great Basin] into two parts, and excercises a decided influence on the climate, soil, and the productions of each.

"Stretching along the coast, and at a general distance of 150 miles from it [here again, the large picture], this great mountain wall receives the warm winds, charged with vapor, which sweep across the Pacific ocean, precipitates their accumulated moisture in fertilizing rains and snows upon its western flank, and leaves cold and dry winds to passage on to the east. [the orographic effect and resulting rainshadow]

"Hence the characteristic differences of the two regions [today's state of California and the Great Basin]--mildness, fertility, and a superb vegetable kingdom on one side, comparative barrenness and cold on the other."

The next paragraph reports on illustrative thermometric observations, and descriptions of seasonal growth of grass, flowers, &c, and ends with,

"Thus December, on one side of the mountain, was winter, and on the other side it was spring."

Frémont's report of his winter crossing of the Sierra in 1844 provides an interesting historical account of weather conditions, both from his descriptions, and from his hypsometrical determinations. For instance, when his last barometer was broken in 1844, he used boiling point observations (graduated to 1/5°f grad) --assumed emersion of the thermometer in snow water, as the Hypsometer was not invented until 1846; but his instrument would have been calibrated in same manner.

On February 20, 1844, at the top of Carson Pass, he recorded a boiling point of 197.5°f. Converting his observed temp to "Hg, and because I know the actual camp elevation where the observation was made, I can reduce it to sea level (30.305'Hg). The further reduction of his observation puts his elevation at 8600', which is nearly on-the-money for the summit of Carson Pass.

Nice Sierra winter weather--a good strong high pressure ridge just sitting there. And because this continued over the next three weeks in 1844, it saved the expedition from disaster.

go Handy formulas to determine elevation by barometer or boiling point and to reduce upper level barometric readings to mean sea level equivalent.
You can also download an Excell spreadsheet to do this for you.

Wonders of modern science department!

We can now see these things happening. This radar image is from an early winter storm December 1, 2001. The section is through the State of California between San Francisco and Lake Tahoe. It shows rain in the valley, changing to mixed rain and snow in the mountains at about 4000', and snow between 5000' and 10,000'. Notice that no precipitation is falling beyond the Sierra Nevada.

This was Gold Medal material! This complete understanding, based on observation and data collection, is enough to have established Frémont's reputation as a Scientist of the first order. (at right, the Gold Medal personally presented to Frémont by Baron von Humboldt for his contributions to geogrphy and science)

I can think of few other examples in American literature of such original clear scientific reasoning, based on observation, leading to such a remarkably correct conclusion--indeed, in four sentences, a complete system. Thoreau's THE SUCCESSION OF FOREST TREES, an address read to the Middlesex Agricultural Society in Concord, Massachusetts September, 1860 would be another.
As here referenced: "Every one has heard that when an American Forest is cut down, a very different vegetation springs up." Charles Darwin, On the Origin of Species, fifth edition, p. 86, 1869

Frémont was the first to scientifically examine and map (and coin the name of) the Great Basin. It is to be remembered that there were then no political boundarys; all being Mexican territory, "California" extended from the Pacific to the Rocky Mountains and north to the line of the present Oregon border.

Directly related to Meteorology:

go The First measurement of the altitude of a high peak (14,000') in North America. My views on the route and the peak conquered by Frémont in the Rocky Mountains in 1842.
A history of Frémont 's training in mathematics, navigation, and mapmaking.
Includes the barometric readings taken on the ascent.
The method of determining elevations by thermometric observations on part of Frémont's 2nd Expedition--Hypsometry.
The mountain barometer.

And:

go Frémont's methods of determining coordinates.
go Frémont's contributions to BOTANY.
go and GEOLOGY
Or, to see a study of the determination of latitudes by Francis Drake, and how the errors in those determinations point to the actual location of his 1579 California landfall.

A brief bibliography:

Blodget, Lorin, Climatology of the United States and the Temperate Latitudes of the North American Continent, J. B. Lippincott and Co., Philadelphia: 1857.
Note: This first really comprehensive (and pioneering) work on the climate of North America contains one reference after another to Frémont's observations.

Frémont, Brevet Captain J. C., Report of The Exploring Expedition to the Rocky Mountains in the Year 1842, and to Oregon and North California in the Years 1843-'44, Printed by order of the Senate of the United States, Gales and Seaton, Washington. 1845.

Frémont, John Charles, Geographical Memoir Upon Upper California, Senate. 30th Congress, Misc. No.148, Wendell and Van Benthuysen, Washington, 1848.

Greely, Gen. A. W., American Weather, Dodd, Mead & Company, New York, 1888.

Goetzmann,William H., Army Exploration in the Americn West 1803-1863, Yale University Press, New Haven, 1959.

Negretti & Zambra, A Treatise on Meteorological Instruments, London, 1864.

Nicollet, J. N., Essay on Meteorological Observations, Printed by order of the War Department, Washington, 1839.

Smithsonian Meteorological Tables [Based on Guyot's Meteorological and Physical Tables] Second Edition (1893) - Smithsonian Miscellaneous Collections - 1032.

Williamson, R. S., On the Use of the Barometer on Surveys and Reconnaissances; part I, Meteorology in its Connection with Hypsometry; part II, Barometric Hypsometry; D. Van Nostrand, New York, 1868.

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©1999, 2007
Bob Graham