Saturday, March 27, 2021

Mapping the Laramie Plains I: in pursuit of the 3rd dimension

"... almost every hill and cañon can be determined at a glance!" From first Laramie, Wyoming Sheet (USGS 1895; public domain).

In the spring of 1893, Albany County Surveyor W.O. Owen received a set of preliminary maps from the US Geological Survey for review. Owen had known what to expect, but the others who saw them were surprised. "The maps are of a very interesting character ...", wrote a reporter for the Laramie Boomerang, "almost every hill and cañon can be determined at a glance!"

Indeed, the new map was astonishing—mountains and depressions around Laramie had been clearly mapped using squiggly lines! But this achievement was long in coming. For millennia, mappers had struggled to show topographical relief, to capture the third dimension on a two-dimensional sheet of paper.

Line + cones = valley
From Amennakhte's map for pharaoh Ramesses IV. Public domain.
In 1160 B.C. Scribe-of-the-Tomb Amennakhte made a map for Egyptian pharaoh Ramesses IV, who was planning a trip to quarry sandstone suitable for statues. On papyrus, he drew a broad winding line with bumpy cones lying flat on either side. With a bit of imagination, we see this is a valley lined with hills.

Amennakhte's hills look terribly crude to our eyes. Yet they aren't all that different from those appearing on maps for the next two millennia. As late as the 16th century, during early exploration of North America, mountains were shown as oversized cones, though sometimes shaded to suggest depth. Often their locations were based on distant views from sea, or rumors.
Leftmost figure is "Royal Scribe of the Place of Truth" Amennakhte. Carving on limestone, ca. 1184–1070 BC. Metropolitan Museum of Art; public domain.

Lewis & Clark map new territory

The next centuries brought significant improvements in surveying and mapping, fortunately. In the early 1800s, the young United States was in desperate need of good maps. The Louisiana Purchase had doubled the country's size. Little was known about the new territory—not even its size, nor how to traverse it.

In May 1804, the Corps of Discovery Expedition, led by Meriwether Lewis and William Clark, headed up the Missouri River in search of a route to the Pacific Ocean. In preparation for the trip, Lewis was trained in celestial navigation. President Thomas Jefferson personally provided instructions for mapping:
"... you will take observations of latitude & longitude, at all remarkable points on the river [e.g., rapids, river mouths, islands]. The interesting points of the portage between the heads of the Missouri, & of the water offering the best communication with the Pacific ocean, should also be fixed by observation ..." [Jefferson assumed they could reach a west-flowing river by carrying their boats overland.] "Your observations are to be taken with great pains & accuracy, to be entered distinctly & intelligibly for others as well as yourself, to comprehend all the elements necessary, with the aid of the usual tables, to fix the latitude and longitude of the places ..."

Lewis and Clark faithfully executed Jefferson's instructions, for three years, four months, ten days and 8000 miles.

William Clark, explorer, soldier, Indian agent, territorial governor & cartographer; portrait by Charles Peale 1810. Public domain.
Clark's map reveals a multitude of mountains

William Clark took on the job of mapmaker. In addition to the Expedition observations, he used information from explorers, trappers, natives, and earlier maps to include areas not covered by the expedition. His first map showed the Corps’ route in great detail and was necessarily huge—50+ large sheets. He then produced a single map 52 inches long and 31 inches wide, engraved and published in 1814: “A Map of Lewis and Clark's Track, Across the Western Portion of North America ...”

Among the discoveries visible on Clark's map is the structure of the Rocky Mountains. They are not a single long ridge as previously thought, but a complex system of mountain ranges and foothills. In fact, after reaching the headwaters of the Missouri, the Corps of Discovery had to travel for weeks on horseback and foot to reach west-flowing waters. A portage across the Rockies was out of the question (click on image below).
Lewis & Clark's Track. Courtesy David Rumsey Map Collection (available in high resolution).
If you click on these images, you can see that mountains were drawn with hachures—short parallel lines looking something like eyelashes. Length and curvature gave a sense of height and steepness. Hachures were denser and darker on east and south slopes of ranges, suggesting a third dimension.

Clark's map was mostly accurate by the standards of the day. But there is a glaring error in the southern part. The Laramie Plains and surrounding mountains are missing! Little was known about the territory that would become southern Wyoming, so future Colorado and Kansas were moved north to fill the gap. This is why the Kanzas [sic] River was shown flowing where Rawlins and Laramie are today.

Today's southern Wyoming, from Lewis & Clark's Track. The Arkansas and Kansas Rivers were mapped hundreds of miles northeast of their true location, putting them in the vicinity of modern-day Rawlins and Laramie (added). Courtesy David Rumsey Map Collection.

The Pathfinder puts the Laramie Plains on the map

John C. Frémont "on the Rocky Mountains"; public domain.

In July 1843, a small contingent of the US Army Corps of Topographical Engineers climbed out of the canyon of the Cache-à-la-Poudre River, where they had hoped to find a route over the Rocky Mountains. Instead, they crossed the broad divide to the north.

In command was a young ambitious lieutenant—John Charles Frémont, the Pathfinder. This was the second of five expeditions he would lead through the American West, each time making significant contributions to geographical knowledge. He also would be court-martialed, lose a presidential election, squander large sums of money in mining schemes, and die in poverty. But all that was far in the future on that lovely summer day when the Laramie Plains came into view.

"The weather was pleasant and cool, we were disturbed by neither musquitoes [sic] nor flies; and the country was certainly extremely beautiful," Frémont would write in his report. "The slopes and broad ravines were absolutely covered with fields of flowers of the most exquisitely beautiful colors. ... As we emerged on a small tributary of the Laramie river, coming in sight of its principal stream, the flora became perfectly magnificent; and we congratulated ourselves, as we rode along our pleasant road, that we had substituted this for the uninteresting country between Laramie hills and the Sweet Water valley."

Challenges: stones, sagebrush, longitude

That evening, they camped on the Main Fork of the Laramie River, where Frémont took astronomical readings to determine latitude and longitude. While latitude seems to have been accurate, his calculation of longitude put them too far west, in the Medicine Bow Mountains near Lake Owen according to Google Earth. But that's not surprising. Estimating longitude was difficult, requiring careful tracking of stars with a precision telescope and a chronometer that kept steady time, or at least lost time at a steady rate.

For three days the party traveled northwest along the Medicine Bow mountain [sic]. The going was easy at first, but near the mountain they were slowed by large round stones in the soil. Equally difficult were ridges "made extremely rough by the stiff tough bushes of artemisia tridentata, in this country commonly called sage" [as it is today].

On August 2, they camped on the Medicine Bow River near "an isolated mountain called the Medicine Butte [Elk Mountain], which appeared to be about 1,800 feet above the plain, from which it rises abruptly, and was still white nearly to its base with a great quantity of snow". Frémont made more astronomical observations, this time including "an immersion [eclipse] of the first satellite of Jupiter." Even so, the calculated longitude again put them too far west.

After passing south of Elk Mountain, the party dropped down to the North Platte River, followed it to the Sweetwater, and continued on to California and Oregon. They would return home in August 1844, after about 15 months and 10,000 miles of travel.

A "meagre and skeleton" but valuable map (Frémont & Preuss 1845). High resolution version here, courtesy David Rumsey Map Collection. 

Dramatic report, spectacular map

Frémont wrote a colorful report about his adventures, with the help of his wife, Jesse, whose father—the powerful Senator Thomas Hart Benton—had secured funding for the expedition. Ten thousand copies were published the following year, to rave reviews. Included was the spectacular “Map Of An Exploring Expedition To The Rocky Mountains” measuring 52 x 30 inches, and stretching from the Missouri River west to the Pacific Ocean and from Los Angeles north to Mt. St. Helens.

However, much of the map was blank—to Frémont's credit. In a Notice to the Reader, he explained: "The map may have a meagre and skeleton appearance to the general eye, but is expected to be more valuable to science on that account, being wholly founded upon positive data and actual operations in the field." Indeed, the map is now considered a milestone, having set a new standard of cartographic accuracy for the American West.

The mapmaker was Charles Preuss, a trained surveyor and topographic artist from Prussia. He would accompany Frémont on three expeditions, making "continuous topographical sketches of the regions through which we passed, and which were never interrupted by any extremity of fatigue or privation" (Frémont's words). The large beautiful maps secured his reputation as a great cartographer.

Cartographer Charles Preuss, date unknown. Source (without attribution).

Laramie Plains up close

In the 30 years since publication of the Lewis and Clark map, techniques for representing relief hadn't changed all that much. Preuss also drew mountains using hachures, though in much greater detail. In the excerpt below (click to view), small narrow drainages are visible on mountains slopes, and low ridges and buttes dot the plains. Preuss varied hachures to show height and steepness. Lower ridges were drawn with shorter lines. Denser darker hachures indicated steeper slopes—for example Laramie Peak (top center of map) and, a short distance southeast, the canyon where the Laramie River crosses the Black Hills (now the Laramie Mountains).

From the 1845 map by Frémont and Preuss. Stars mark points where longitude and latitude were determined. At triangles, they measured the sun's height at noon to estimate latitude.

However, if we continue our examination, we're soon confused. Is that low mountain range paralleling the Medicine Bows Jelm and Sheep Mountains? Doesn't look right. Nor does the ridge east of the Main Fork. Most puzzling is the “Right Hand Fork” which (supposedly) joins the Main Fork of the Laramie River before it enters the canyon. Our history buffs still haven't solved this mystery.

Errors at this scale aren't surprising. With the great expanse of unknown territory ahead, there was little time for finer details, and though Preuss' map was highly accurate in its time, it's a far cry from the "very interesting map” showing every hill and canyon, which would so excite a Boomerang reporter 50 years later ...

[More to come in Part II.]

This post is based on the first of two articles about mapping the Laramie Plains, my most recent contribution to the "Laramie History" column in the Laramie Boomerang.

Sunday, March 14, 2021

Tree-following: Let it Snow!!


Two days ago, I took a few photos of Flash and Spike, the trees I'm following this year. As you can see, there's nothing left of the little bit of snow that was on the ground a month ago. It's been dry, dry, much too dry!! My too-big-to-water yard is covered in native grasses adapted to xeric conditions: western wheatgrass, alkali sacaton, prairie saltgrass. Even they are struggling after several years of drought. But they're tough. One day, their normally vigorous selves will return.

I water the young trees whenever temps rise above 40º F, to encourage root growth. But there are no obvious changes above ground, it's too early. So I checked their twigs to identify them using buds and scars. Of course I already know what they are. This was a chance to examine features I usually ignore.

I pulled the Winter Tree Finder out of my stack of tree-finders. These are dichotomous keys at their best—simple and fun. One got me hooked on tree id 50 years ago. With the handy twig diagram and friendly descriptions, I was able to find the various buds and scars, and make my way through the key.

For Spike, I didn't get beyond p. 4: "Sometimes a conspicuous feature ... makes identification easier." There were just two candidates with conspicuous thorns, Honey Locust (nope) and Hawthorns (yes), p 21, where I stopped because: "Hawthorns are far too numerous to cover here."
Spike the Hawthorn, with conspicuous thorns and alternate lateral buds.

With Flash, I made good use of the key, moving smoothly through the dichotomous questions. Tree a conifer or not? NOT. Leaf scars alternate or opposite? OPPOSITE. This year's twig more or less than ¼ inch wide? LESS. Leaf scars narrow, inconspicuous, with 3 bundle scars? YES. Terminal bud egg- or cone-shaped? YES. "It is a MAPLE, go to p 48" where I landed amid many maples, none of which grow here (the book covers midwestern and eastern North America).

Unfortunately, the buds and scars of the slender twigs were hard to photograph even though the wind was just a gentle breeze. I didn't dare cut twigs to photograph inside ... these young trees look like they need every twig they have. Here is my best shot, in fact, my only decent one.

Flash the Maple.

I waited until this morning to post, as I was hoping the weather forecast was correct. It was close! Now the scene is very different. The snowfall is going to be "absolutely historic" according to the weather news. If that's the case, then I must be prehistoric! But it IS a lot of snow, and quite wet. The plants and I are happy 😊 

This is my contribution to the monthly gathering of tree-followers hosted by The Squirrelbasket. More news here. Join us!