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Scientific Instruments

This list compiled from The Expeditions of John Charles Frémont, Vol. 1, edited by Donald Jackson and Mary Lee Spence, University of Ilinois Press, 1970.

All of these were not used on any particular survey or expedition; they are only representative of the variety of instruments used.

(*Instruments mentioned in letter or report--there may be some duplication.)


Vouchers 1838-39:

1 chronometer chain

Repair of sextant

Chronometer box

Repair of barometer

Repair of microscope

Repair of magnetic compass

2 mountain barometers

2 cases for same

6 pocket thermometers

6 dark glasses

3 magnifiers

1 Troughton's reflecting circle and stand
(necessary when mearuring an angle of larger than the 120 degrees of the sextant--as when measuring the height of the sun using an artificial horizon when it is over 60 degrees above the true horizon.)

1 English nautical almanac 1839

1 American nautical almanac 1839

1 English nautical almanac 1840

1 Variation chart

8 Pocket thermometers

2 of same

1 compass in gimbals

5 lb quicksilver [for artificial horizon]

Logarithm tables, Callet

1 case for telescope

1 sextant cleaned and varnished

1 magnifying glass and movement

2 barometers filled and new tubes

1 brass frame to magnifying glass

1 maqnifying Glass with Wood frame

1 artificial horizon repaired

cleaning vertical circle

cleaning telescope

magnifying glass and tube to small sextant

2 leather cases for barometers

1 leather case for sextant

cleaning and repairing one patent gold duplex watch

3 common [watch] keys

1 [watch] guard chain

2 watch glasses

cleaning and repairing silver watch

Vouchers 1841:

1 dipping needle apparatus, stand and case

1 magnetic needle [for compass]

1 double magnifier

repairing mountain barometer

repairing barometer in tripod

1 1/2 lbs mercury [for artificial horizon]

1 thermometer

1 compass

for making 1 box to serve as case for mercurial horizon

cleaning and repairing chronometer

1 leather cover for sextant

for a new detant spring, new ruby pellet [pallet], adjusting and cleaninq a silver pocket chronometer

1 Buquet's chronometer

* 150 power telescope [astronomical]

Vouchers 1842:

1 sextant

1 circle

1 mountain barometer repaired

1 ditto

1 ditto

1 thermometer (at least one was remarked to be calibrated in 1/5 degrees for determining the boiling point of water--it was broken in the Wind River area)

1 ditto

2 leather cases for barometer

repairing sextant, 3 shades, eyepiece, &c

case for dipping needle

1 hydrometer, Beaume

repairing sextant, regulating, &c

repairing horizon box

Troughton sextant and case

Refitting the hook inside the mainspring, resetting and brazing anew the cock diamond, polishing pivots, poising the balance, cleaning, reducing, and ascertaining the rate of the chronometer by Brockdank No. 739

1 Massey's patent log

repairing and cleaning a sextant

additions to a camera lucida

20 spiral springs for chronometer box

1 case for spyglass

1 English nautical almanac

1 new balance staff and cleaninq chronometer

mirror for camera obscura [for sketching landscape scenes]

1 first class 2-day London chronometer by French, No. 7810

1 land-carriage outside box, with extra pillows, cushion, &c. [for transporting the above to avoid shock]

1 mountain barometer in leather case

4 best thermometers in mahogany case, graduated to order

2 lbs. best refined quicksilver, box and bottle [for artificial horizon]

1 mountain barometer

leather case for same

1 boat compass

1 best quality French pocket compass

1 German pocket compass

1 common pocket compass

1 best quality thermometer

1 magnifying glass

1 pair forceps

1 magnet

1 set Daguerreotype apparatus

25 polished Daguerreotype plates

1 pocket microscope

1 barometer

* sextant

* theodolite

* 2 surveyor's compasses

Vouchers 1843:

American and English Nautical Almanacs

*1 Reflecting circle by Gambey
(necessary when mearuring an angle of larger than the 120 degrees of the sextant--as when measuring the height of the sun using an artificial horizon when it is over 60 degrees above the true horizon.)

*2 Reflecting sextants by Troughton

*1 Pocket chronometer by Goffe

*1 Pocket chronometer by Brockbank

* 1 Syphon barometer by Bunten

* 1 Cistern barometer by Freye & Shaw

* 6 thermometers

1 Daguerreotype apparatus

1 Daguerreotype apparatus

1 telescope [astronomical] by Frauenhofer

* 1 spyglass

2 artificial horizons

2 pocket compasses

1 barometer;

5 thermometers

repair of chronometer

1 silver 2-day pocket chronometer

2 pocket compasses

1 ivory scale


reflecting circle


Preuss, June 16, 1842:

"Our big chronometer cannot stand up under transport by wagon; it will probably have become useless for finer observations."

Cf. Major W. H. Emory, October 14, 1846:

We parted with our wagons, which were sent back under charge of Lieutenant Ingalls, and. in doing so, every man seemed greatly relieved. With me it was far otherwise. My chronometers and barometer, which before rode so safely, were now in constant danger. The trip of a mule might destroy the whole. The chronometers, too, were of the largest size [cased and gimbaled], unsuited to carry time on foot or horseback. All my endeavors, in the 24 hours allowed me in Washington to procure a pocket chronometer had failed. I saw then, and I now feel, the superiority of pocket over large chronometers for expeditions on foot or horseback.

pocket chronometer



Preuss, July 25, 1942:

We left the large chronometer in Laramie; Fremont succeeded in making it run again, and he was jubilant when he heard again the ticking and tick-tocking. In comparing it we found, however, that every 24 hours it went wrong by about one hour. Oh, you American blockheads!



Preuss, July 25, 1942:

"A barometer, not the best one though, has gone wrong. The bad road between here and Laramie killed it.




Frémont, August 10, 1842:

"As soon as the camp was formed, I set about endeavering to repair my barometer. As I have already said, this was a standard cistern barometer of Troughton's construction. The glass cistern had been broken about midway; but as the instrument had been kept in a proper position, no air had found its way into the tube, the end of which had always remained covered.I had with me a number of vials of tolerably thick glass, some of which were of the same diameter as the cistern, and I spent the day it slowly working on these, endeavoring to cut them to the requisite length; but, as my instrument was a very rough file, I ivariably broke them. A groove was cut in one of the trees, were the barometer was placed during the night, to be out of the way of any possible danger, and in the morning I commenced again. Among the powder horns in the camp, I found one which was very transparent, so that its contents could be almost as plainly seen the as through glass. This I boiled and stretched on a piece of wood to the requisite diameter, and a scraped it very thin, in order to increase to the utmost it's transparency. I then secured it firmly in its place on the instrument, with strong glue made from a Buffalo, and filled it with mercury, properly heeded. A piece of skin, which had covered one of the vials, furnished a good pocket, which was well secured with a strong thread and glue, and then the brass cover was screwed to its place. The instrument was left some time to dry; and when I reversed it, a few hours after, I had the satisfaction to find it in perfect order; it's indications being about the same as on the other side of the lake before it had been broken."



Frémont, November 21, 1843:

"Mr. Perkins walked with Mr. Preuss and myself to the heights, about nine miles distant, on the opposite side of the river [Columbia], whence, in fine weather, an extensive view may be had over the mountains, including seven great peaks of the Cascade range; but clouds, on this occasion, destroyed the anticipated pleasure, and we obtained bearings only to three that were visable: Mount Reguier[sic] , St. Helens, and Mt. Hood. On the heights, about one mile south of the mission, a very fine view may be had of Mount Hood and St. Helens. In order to determine their position with as much accuracy as possible, the angular distances of the peaks were measured with the sextant, at different fixed points from which they could be seen."


Cf. Major W. H. Emory, Santa Fe, September 14, 1846:

To Lieutenant J. W. Abert:
If your force is sufficient, the operation described in the last paragraph may be carried out simultaniously with the triangulation. You are aware that I have no theodolite at my disposal; the triangulation must, therefore, be made with the sextant.




Preuss, 0ctober 10, 1943:

"Half-passed ten in the evening. I am sitting alone by the fire to watch till twelve o'clock, when an immersion of satellites will occur. To tell the truth, I wish the dear Lord had not attached any satellites to Jupiter. One can loose one's mind over it. These immersions occur so often that one forgets how to sleep."

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Theodore Talbot, Bent's Fort, July 3, 1845.

"...the Captain [Frémont] is very kind to me. I shall be with him in making time and notes etc. fo his observations I Hope.


Theodore Talbot, Bent's Fort, August 16, 1845.

"Capt. F. has been much occupied with his transit Insmt. at which Mr. King assists him, & in other astronomical & meteorological obsnvs. in which I assist him. We are waiting here now for a moon culmination to determine the longitude of this place with the Transit Instrument."




Charles Preuss, October 22, 1843

"One can almost kill pheasants with a stick. If I could have a rifle on my back instead of the barometer, I could shoot the most magnificent dinner."





Joseph Nicollet, 1837

"I carried my sextant on my back, in a leather case, thrown over me as a knapsack; then my barometer slung over my left shoulder; my cloak, thrown over the same shoulder, confined the barometer closely against the sextant; a portfolio under my left arm; a basket in the hand, which contained my thermometer, chronometer, pocket compass, artificial horizon, tape line and so forth. On the right side, a spy-glass, powder flask, and shot bag; and in my hand, a gun or an umbrella, according to the circumstances."

Here an instrument that was the personal property of John Frémont.
The present owner writes:
"I've sent you some pictures of Frémont's telescope. I bought it from my wife's grandfather who had bought it from Frémont's daughter Elizabeth [Benton] Frémont in Los Angeles. I've had it over 35 years and am going to sell it. I would like to see it in a museum or library.  I do not know how long my wife's grandfather had it, but I would think over forty years [Elizabeth died in1902]. If you know of anyone or organization that would want to purchase it, I would appreciate any help."

The telescope is apparently of mid-19C English manufacture, and has the initials JCF engraved in copperplate script.

Closed length is approximately 24" and the object lens approximately 3" diameter.
This website will contact the owner for those interested.

©1999, 2007
Bob Graham