Wednesday, April 14, 2021
Friday, April 9, 2021
|Two views of Sheep Mountain[s]: 1895 USGS map and 2011 photo looking northwest from Sodergreen Lake.|
To refresh your memory, and for you who missed Mapping the Laramie Plains I: in pursuit of the 3rd dimension, this story began with the promise of a map of the Laramie area on which "almost every hill and cañon [sic] can be determined at a glance!" according to the Laramie Boomerang in 1893. Yet the post ended before we could share in the reporter's excitement. That's because the back story was so long—three millennia.
It began in the 12th century B.C., when Egyptian scribe Amennakhte drew the earliest surviving topographic map—a map which shows the shape of the land. It featured a winding line with large flat cones on either side—a valley bottom between hills. Maps would be similarly crude for the next three thousand years, with hills and mountains drawn as simple pictures, and approximately located at best.
But by the early 1800s, techniques were much improved. Maps by William Clark of the Lewis and Clark expedition, and Charles Preuss, John C. Frémont's cartographer, added significantly to our geological knowledge. But they weren't perfect. Clark put today's Colorado too far north, thereby eliminating the Laramie Plains. Preuss's map was accurate for major features, but finer details could be unreliable. And on both maps, mountains were shown using hachures—short parallel lines suggesting relief but with little specific information. The third dimension remained elusive.
|Excerpt from Preuss's map, showing the Laramie Plains crossed by the mysterious Right Hand Fork of the Laramie River (state line added). David Rumsey Map Collection.|
After a grim hiatus, mapping resumes
Through the 1850s, the Army Corps of Topographical Engineers continued to explore and map the American West. The emphasis was route-finding, exemplified by the Pacific Railroad Survey—four concurrent expeditions looking for a way across the Rocky Mountains. But mapping came to a halt with the start of the Civil War, except as needed by the Union Army.
About five years after the War's end, the government began to invest again in maps. They were badly needed, for while France and England were putting final touches on national maps, and a dozen more countries had surveys in progress, the United States lagged far behind.
In 1870, a young US Army Lieutenant, George Montague Wheeler, presented a detailed proposal to map the United States west of 100º longitude (which roughly bisects the Dakotas). In need of post-war work, the Corps of Topographic Engineers jumped at the opportunity, and in 1871, Wheeler launched his "Survey West of the One-Hundredth Meridian."
|George Montague Wheeler ca. 1872; National Portrait Gallery (SI)|
Where on Earth are we?
Just a year later, on November 30, 1872, James H. Hayford of the Laramie Daily Sentinel reported, "Some parties are putting up some aparatus [sic] and a temporary observatory near our office today, under the supervision of Lieut. Wheeler [it's unlikely Wheeler himself was present], for the purpose of taking some astronomical observations to determine the latitude and longitude of this place."
Wheeler's men, John H. Clark and F.R. Simonton, had already made astronomical observations at two other locations in Wyoming Territory: Fort Fred Steele and Cheyenne, where they came up with a handy improvement to standard procedure. "A large wall-tent drawn over a framework formed the observatory. ... it was found to be an improvement to retain the ridge-pole [during observations] as a support against the violent winds so prevalent."
All in all though, working conditions were luxurious compared to those of the Frémont expedition 30 years earlier. Clark and Simonton could partake in the conveniences offered by the Laramie City, just four years old. Furthermore, their tent "was furnished with all the appliances of a field and temporary observatory, such as stools, stands, tables, and the like, and nothing was wanting as to equipment for first-class field-work. The [local] telegraph company furnished the line."
Longitude by wire
However, one thing hadn't changed since Frémont's time—longitude remained the greater challenge. There was no way to measure it directly. Instead, it was calculated based on the difference in time of specific celestial events in Laramie, and in Salt Lake City where longitude had been determined in 1869. [If you are thinking Laramie and SLC are in the same time zone, you're correct. But for this procedure, the surveyors used local time, also called solar time.]
To determine time difference, Clark and Simonton relied on the near-instantaneous communication of telegraphy. Time was recorded by chronograph—a combination of chronometer (clock) and paper-covered cylinder. Powered by a small battery, the cylinder turned exactly once per minute, as a pen marked a chronometer tick every second. After each minute, the pen-holder advanced slightly. The result was a piece of paper covered in parallel lines of tick-marks, a printed record of time.
As the chronometer clicked and the cylinder turned, the men added astronomical observations to the chronograph record, in real time. One man kept an eye on the heavens while also recording meteorological conditions and other notes on a paper form. When a star to be tracked approached, he notified the Observer at the telescope. At the moment the star entered the telescope's field of view, the Observer tapped a key wired to the chronograph, thereby leaving a mark on the paper. He did the same when the star passed out of view.
|Drum chronograph by William Bond & Son, ca. 1850; "an instrument that touched a pen to a paper-wrapped cylinder to record both the beats of the clock and the instant of a celestial event, signaled when an observer pressed a telegraph key." (courtesy National Museum of American History)|
This was only half the project. Each time the Observer in Laramie pressed the key, the signal also was sent via telegraph to a chronograph in Salt Lake City, overseen by their coworker, E.P. Austin. From the two sets of long paper records, they determined that stars passed over Laramie 25 minutes and 12 seconds before passing over Salt Lake City, putting the Laramie observatory at approximately 105º 35' 24" longitude (only about four blocks too far east according to Google Earth, not bad for field data!).
Star-gazing in Laramie, Wyoming in December
Obviously, Clark and Simonton were able to determine longitude much more accurately than Frémont had three decades before. But the work was challenging even so. They had constructed a rigid base for their instruments, but thundering trains shook them out of adjustment, and the metal contracted and expanded with temperature. Ink froze on the coldest nights, and the men's concentration waxed and waned with weather and amount of sleep.
So for accuracy, multiple stars were observed on multiple nights—but only when skies were clear at both ends of the telegraph line. To get enough observations, Clark and Simonton spent most of December in Laramie, "subjected to too much cold and too many wind and dust storms for any human brain and muscle to effect its best work in astronomy," according to Clark.
The future arrives
|Wheeler's 1877 Progress Map; published sheets are brown. Laramie is near the east edge of Sheet 43. David Rumsey Map Collection.|
In just eight years, Wheeler's crews surveyed 333,000 square miles; 75 topographic atlas sheets were produced (but no Laramie Sheet). The tradition of representing relief using hachures continued, often with the addition of spot elevations (numbers). But there was a revolution afoot. During the same time, John Wesley Powell and Almon Harris Thompson, of the US Geographical and Geological Survey of Territories, were producing topographic maps using contour lines, which connected points of equal elevation. These maps showed the shape of the land in greater detail and more accurately.
|Excerpt from Wheeler's hachured "Central Colorado Atlas Sheet # 62a" (1878). Click to view scattered spot elevations. David Rumsey Map Collection.|
|Excerpt from Powell and Thompson's contour map: "Green River from the Union Pacific Rail Road [WY] to White River [CO]" (1876); green marks irrigable land. David Rumsey Map Collection.|
|Excerpt from "Plate 170B: Special types of lakes: part of Laramie Sheet" showing hollows or sinks of the Laramie Plains (USGS 1908).|