Alexander von Humboldt's Latin American Expedition (1799-1804)

Alexander von Humboldt’s Latin American Expedition (1799–1804)

Instruments, Geography & Botany

An Exhibit in Celebration of HSU's Centenary

Richard Paselk, Curator

As we celebrate HSU's Centennial, it is appropriate to remember our namesake, Baron Alexander von Humboldt, a true embodiment of the “Humboldt Spirit” as an explorer, scientist, and advocate of social justice. This display emphasizes the five-year expedition to Latin America that made Humboldt’s reputation, focusing on his science. continued below case image ...

Objects on the left side of the case may be accessed via links in the list below

Objects on the right side of the case may be accessed via links in the list below

Object pages may also be accessed by links within the short essays below.

Descriptive pages for most artifacts include links to examples/descriptions of instruments from Humboldt's time to put the more recent objects displayed in context.

In Humboldt's own words:

I shall collect plants and fossils, and with the best of instruments make astronomic observations. Yet this is not the main purpose of my journey. I shall endeavor to find out how nature's forces act upon one another, and in what manner the geographic environment exerts its influence on animals and plants. In short, I must find out about the harmony in nature. —Alexander von Humboldt, Letter to Karl Freiesleben (Jun 1799).

In this pursuit Humboldt carried a wide selection of the finest scientific instruments by the best makers of his day. Over forty instruments are listed in his Personal Narrative of Travels…(read a pdf of Humboldt's instrument list from: Alexander von Humboldt. Personal narrative of travels to the equinoctial regions of the New continent, during the years 1799-1804, by A. von Humboldt and A. Bonpland. translated from the French by Helen Maria Williams, 1814, pp 34-40). They enabled him to measure location (longitude and latitude), altitude, chemical composition of air and water, electrical activity, intensity of light, sky color, etc. On display are a few 19th and 20th century artifacts representative of a fraction of Humboldt’s collection.

Instruments for Geography

One of Humboldt’s major accomplishments on his expedition was to accurately determine latitudes and longitudes for the major cities and geographic features he visited in Latin America (see the map on the right). Instruments used for these measurements include the three-foot achromatic telescope to determine Greenwich Mean Time (GMT) by observing celestial phenomena such as eclipses of the Galilean moons of Jupiter and the transit of Mercury across the Sun, and comparing the times to precisely tabulated and published values. Longitude was then found by comparison of GMT to local time from one of his two chronometers set by noon solar observations using a sextant. GMT could also be determined using the large sextant by measuring “Lunar distances” (the angular position of the moon relative to fixed celestial objects such as the sun or stars) and comparing them to tabulated values via an arduous series of calculations. Latitude was discovered, using either the large sextant or the “snuffbox-sextant”, by observing the Sun’s height above the marine horizon, or using an artificial horizon (he listed three: mercurial, crystal, and glass). Humboldt also used his sextants for a variety of other purposes, e.g. laying down the paths of rivers, measuring angles from horseback etc., or discovering how high condors flew by measuring the wingspread angle and calculating altitude using trigonometry and a known wingspread.

Instruments for Physical Measurements

Most of the rest of Humboldt’s instruments were intended to measure local physical phenomena. He used a dip Circle to measure the angle of Earth’s magnetic field, a property that changes with latitude and with the presence of iron-ore deposits. One of Humboldt's favorite instruments, as seen by its appearance in both paintings, was his barometer/altimeter, which he carried with him constantly, determining altitudes all along his journey. A hypsometer allowed him to determine the boiling point of water with a thermometer at various altitudes and locations. He carried at least four additional thermometers to measure temperature. The Leyden jar was used to collect electrical charge in Humboldt’s various electrical observations and to provide a source of electric sparks to ignite mixtures of gas in determining the oxygen content of the atmosphere using one of the eudiometers in his kit. Finally, he needed to place his observation and collecting localities into the known geography based on landmarks etc. using the theodolite, a key tool of the surveyor. Instruments not represented in this display included those for measuring the color of the sky, barometers and barometric tubes, electrostatic (e.g. galvanic) apparatus, a surveyors chain, a standard meter, an assay balance, a rain gauge, evaporation rate dishes, absorption tubes to measure CO2, hygrometers, a magnetometer, a variation compass, etc.

Plant Collection & Identification

Humboldt and his expedition companion/collaborator, Aimé Bonpland, collected over 60,000 plant specimens representing over 6,000 species, of which more than 3,000 were new to science. One of the thousands of resulting engravings commissioned by Humboldt with his own fortune after the expedition is shown in the open book. A specimen from the HSU herbarium of the same species is next to the illustration. The gold frame behind them contains one of Humboldt’s own original drawings (left) and the engraving made from it (right). Finally, Humboldt and Bonpland used a microscope as an aid in identifying and characterizing specimens as well as observing small items and details of all kinds.