RSS News


    Return to...
The ExpeditionPhiladelphia ConnectionsAstronomy Notebook

Editor's Foreword

Page 1 of 13


prepared for

Captain Meriwether Lewis


Robert Patterson

Philadelphia, Pennsylvania, 1803

nown now as the “Astronomy Notebook,” this extraordinary document has been an obscure and often neglected detail in the history of the Lewis and Clark Expedition. Yet there are few other pre-expeditionary documents that are equal to it in importance, for it contains the keys to the fulfillment of Jefferson's primary charge to Lewis: "Beginning at the mouth of the Missouri, you will take observations of latitude & longitude, at all remarkable points on the river, & especially at the mouths of rivers, at rapids, at islands, & other places, . . . as that they may with certainty be recognised hereafter. . . . The variations of the compass too, in different places, should be noticed." All those observations were to be taken, he emphasized, "with great pains & accuracy," and ultimately submitted to the Secretary of War, who would have the calculations completed "by proper persons."2

Although no author’s name appears on the document, it clearly is the work of Robert Patterson of Philadelphia, Pennsylvania. His authorship is easily traced through reference to a letter that Patterson wrote to Thomas Jefferson on March 15, 1803,3 in which Patterson detailed his method for computing longitude from an observation for Lunar Distance. The formulation stated there is essentially identical to that expressed in Problem 5 of the Notebook. But there is additional confirmation of the authorship . . .

Following Problem 5 in the Notebook are several pages of a “Statistical Table” in Lewis’s hand. In another letter to Jefferson,4 Patterson writes:

Philada. June 18th 1803.


I recommended to Capt. Lewis the use of a Statistical Table in which to set down his astronomical observations, in the course of his intended expedition; as an expedient that would save a great deal of time, and be productive of many other obvious advantages. I had proposed to draw him out a sketch of such a table, but an unusual hurry of business prevented me, while he was in the city. I have now, however, fulfilled my promise and transmit the inclosed for his inspection.

I have sent it under cover to you, Sir, lest Capt. Lewis may have proceeded on his tour; in which case, if you shall judge it worth his notice, you will have the trouble of forwarding it to him. I am Sir with the highest respect & esteem your Obedt. Servt.

R. Patterson

Lewis must have made a copy of the statistical table for his field use on his trip. Following this table there are two pages, also in Lewis’s hand, explaining his procedures for taking and recording astronomical observations together with an entry from Point of Observation No. 21 at the mouth of the Musselshell River (May 20, 1805).

In May 1995, Arlen J. Large of Washington, D.C. sent me a copy of the Notebook, having made it from a copy that he had received from Gary Moulton. The pages were 7 inches tall by 6 inches wide. As can be expected, the copy (written in the script of the early 1800s), was badly faded in some places, and correspondingly difficult to transcribe.

Determining illegible numbers was a problem only where those numbers could not be derived by performing mathematical operations. Thus, for example, when Patterson gives a series of numbers for "exercises," it is possible that some misinterpretations were committed.

Abbreviations have been replaced with the spelled-out word unless space in the forms did not permit it. Degree (°), minute (') and (") marks have been added where they were omitted in the original or expressed only as a ditto sign ("). The words latitude and longitude were almost always capitalized, but not consistently so. They are capitalized here only at the beginning of a sentence.

Only a few additional punctuation marks have been added and those only where ambiguity might otherwise occur. The pages in the manuscript Notebook are unnumbered; page numbers have been inserted in brackets for readers who wish to compare this edition with the original.

Mathematic symbols have been replaced by the word they represent except where there were space limitations in the Forms. They are:

= angle
= moon
= sun
= star

Patterson made a few errors in his numbers and mathematics. They have been identified with footnote symbols in brackets.

Despite Patterson's assurance to Thomas Jefferson that his astronomical formulas would be "extremely easy even to boys or common sailors of but moderate capacities," it will soon be obvious that only readers with a working knowledge of trigonometry will find Patterson's didactic little notebook comprehensible, or even interesting. But then, Lewis evidently had had little or no exposure to higher math prior to his crash courses with the astronomer and surveyor Andrew Ellicott in Lancaster and with Patterson in Philadelphia — in a time span of no more than a few weeks that was crowded with a myriad of other pre-expedition details and obligations. However, anyone should be able to appreciate what a challenge Lewis faced in trying to comprehend these concepts and learning to use them. Indeed, the sheer weight of it should inspire even greater admiration for this young officer for his fortitude in taking on this challenge along with everything else.

Robert N. Bergantino
Butte, Montana
July, 2005

1. Meriwether Lewis Astronomy Notebook, 1803-1805, Western Historical Manuscript Collection – Columbia, Missouri. The Notebook was purchased from a private collector in 1928 by the State Historical Society of Missouri as part of the Breckenridge Collection. This is the first appearance of the entire document in print. The editor gratefully acknowledges the assistance of William T. Stolz, Senior Manuscript Specialist, WHMC-Columbia.

2. Autograph document signed; sender's copy (Library of Congress). Reprinted in Donald Jackson, ed., Letters of the Lewis and Clark Expedition with Related Documents, 1783-1854, 2d ed., 2 vols. (Urbana: University of Illinois Press, 1978), 1:61-62.

3. Ibid., 1:28-31.

4. Autograph letter, signed; recipient's copy (Library of Congress). Jackson, Letters, 1:56.


From Discovering Lewis & Clark ®, http://www.lewis-clark.org © 1998-2014
by The Lewis and Clark Fort Mandan Foundation, Washburn, North Dakota.
Journal excerpts are from The Journals of the Lewis and Clark Expedition, edited by Gary E. Moulton
13 vols. (Lincoln: University of Nebraska Press, 1983-2001)