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from Laying Down the Lines
In our minds’ eye, we see Canada stretched out on top of one side of the globe, set apart from Europe by the great blue-green Atlantic. But this clear sense of where we are on the globe was once not so. The seventeenth-century navigators, setting out from Europe, knew where they were in relation to the equator, as they could establish latitude with relative ease by measuring the angle of the Pole star (Polaris) above the horizon, or the position of the sun at noon. How far they had sailed in an easterly or westerly direction was more problematic. Longitude was generally calculated by dead reckoning, often with disastrous results and loss of life. Longitude, the angular distance east and west measured from the meridian that runs through the British observatory established at Greenwich in England in 1676, can be easily determined from the difference between Greenwich time and local time. Longitude is expressed in degrees or minutes, the complete angular distance around the world being 360 degrees. Each 15º is equivalent to one hour’s local time difference. Therefore, if local time can be established in relation to Greenwich time, it is possible to figure out one’s position in degrees of longitude. By correlating it with degrees of latitude, a global location can be established. From 1676 British cartographers based their work on Greenwich time. In 1880 Greenwich Mean Time was established, and in 1884 the meridian passing through Greenwich was adopted as the world’s prime meridian at 0º longitude, from which all nations orient their maps.
An early method of finding Greenwich time was to make astronomical observations of eclipses of the moons of Jupiter. These difficult and lengthy procedures required perfect conditions for any accuracy, and were almost impossible at sea. In 1714 the British Parliament offered a huge reward to the man who could devise a simple method of measuring longitude. The solution rested on a simple but elusive device—a clock to keep accurate Greenwich time that could be carried far from the shores of England. The clocks invented by John Harrison of Britain between 1730 and 1770 ultimately resulted in the use of large, expensive chronometers on board ships.
In the Canadian North-West, however, astronomical observations remained the only way to establish coordinates for surveying. Initially, in the late eighteenth century, they were approximations, but instrumentation improved as the nineteenth century progressed and levels of accuracy increased. Although pocket chronometers were available by the mid-nineteenth century, they remained fragile and unreliable instruments. Rough travel over land caused inaccuracies, forcing the surveyors to take astronomical observations to verify Greenwich time. Finally, the new technology of the telegraph meant that simultaneous Greenwich time could be checked through linked observatories, and communicated to wherever the telegraph system extended.
Surveys in the Interests of Great National and Economic Rivalries
While the scientific problem of longitude was preoccupying European mariners, a power struggle on land in the New World led to the first exploratory surveys. As soon as the Hudson’s Bay Company (HBC) began to trade for furs with the Aboriginal peoples of Canada from the shores of Hudson Bay, from 1670, Britain and France vied for control of the vast territories of the North-West. The French fur traders of New France who controlled the St. Lawrence River moved westward, establishing trading posts to exchange European goods for furs with Native peoples. By 1754 the HBC, alarmed by their competitors’ western inroads and success, sent out Anthony Henday to win back some ground with the help of Native guides whose survival skills on the land ensured his safe travel. Henday over-wintered in the foothills of central Alberta before making it all the way to the Rocky Mountains, where the French had not yet gone. In the same year, 1754, Britain and France went to war in North America, and two years later the hostilities expanded to a worldwide conflict, generally referred to as the Seven Years’ War, involving the colonial powers of Europe. In North America, the tide turned in favour of the British, and New France fell in 1760. Britain claimed control of Canada through the Treaty of Paris in 1763, and French traders lost control of the St. Lawrence. Little changed in the fur trade, however, as it did not take long for English-speaking independent traders operating from Montreal to take up the slack.
Among those independent Montreal traders pushing westwards in competition with the HBC was Peter Pond. In 1778 he discovered a significant portage—Methy Portage—connecting the Churchill River system with a stream flowing westwards into the Athabasca River. Pond’s report on the rich fur resources of Lake Athabasca, along with a number of his maps—the first of the western interior of Canada— soon had the attention of the HBC. Pond, however, used a compass and guestimates to establish longitude. His estimates placed Lake Athabasca less than a hundred miles from the Pacific! When the HBC compared Pond’s claims with results determined from longitude established on the charts of Captain James Cook, who had mapped the Pacific coast of Canada, the dilemma was clear. Was Pond incorrect or had he found a short route to the west coast that would give Britain access to Asia?
The dilemma awakened the Hudson’s Bay Company to the value of accurate maps of the North-West based on astronomical observations. The company hired British practical astronomer Philip Turnor, compiler of the Nautical Almanac issued by the Royal Greenwich Observatory, as its surveyor. His job included the training of others within the company to make astronomical observations, before he finally travelled to Lake Athabasca to establish its coordinates in 1790. Peter Fidler, one of his two most famous students, went with him. However, David Thompson, Turnor’s second student, ultimately proved to have a greater impact on the history of surveying in Alberta.
David Thompson—Alberta’s Legendary Exploratory Surveyor
“In the month of May 1784 at the Port of London, I embarked in the ship Prince Rupert belonging to the Hudson’s Bay Company, as apprentice and clerk to the said company, bound for Churchill Factory, on the west side of the bay.” So began the adventure that would last a lifetime for fourteen-year-old David Thompson, who had shone at mathematics at London’s charity Grey Coat School near Westminster Abbey. By September he found himself at Churchill Factory in a world of approaching winter. In fall 1785 Thompson was summoned to York Factory, some 150 miles south, to depart on exploratory travels to expand the fur trade into the country that would later be part of Alberta. The HBC had renewed concerns about rivalry when the independent Montreal traders amalgamated their interests to form the North West Company in 1784. By 1787 Thompson had paddled upstream along the North Saskatchewan River, travelling overland southwest to the Bow River in 1788.
A leg injury caused David Thompson to spend the winter of 1789–90 at Cumberland House on the North Saskatchewan River, in present-day eastern Saskatchewan. At the beginning of October 1789, Philip Turnor, the Hudson’s Bay Company’s surveyor, arrived by canoe. “This was a fortunate arrival for me,” Thompson recalled. “Under him I regained my mathematical education, and during the winter became his only assistant.” Thompson eagerly devoted himself to making astronomical observations to establish the exact location of Cumberland House. He had caught the surveying bug, but he was unable to accompany Turnor on his travels to Lake Athabasca in spring 1790 due to a severe inflammation of his right eye, which he blamed on “too much attention to calculations in the night.” Peter Fidler, who had also been training at Cumberland House under Philip Turnor, took Thompson's place. By the next year, Thompson had recovered his health, and his apprenticeship in the trade was complete.
Thompson was sent west to establish trade relations with Native trappers. The HBC informed Thompson that any information that “can tend to form a good Survey and Map of the Country Inland (sic) will always be particularly acceptable to us.” The company presented him with a compass, a thermometer, and a case of instruments, and by 1794 gave him a raise—at his own request—of 400 percent! He was charged with the task of finding an efficient route from Hudson Bay to Lake Athabasca. Nevertheless, in 1797 Peter Fidler was appointed chief surveyor and mapmaker to the HBC. Thompson left the HBC abruptly, despite an excellent salary and approval of his performance as trader and surveyor, to join the rival North West Company. Thompson and Fidler bore a lifelong hostility as they pursued their jobs as surveyors to rival companies that would not merge until 1821. Personality issues and money aside, Thompson must have thought the North West Company offered more freedom to survey new routes.
The North West Company was happy to have a surveyor and generously supplied Thompson with canoes, horses, men, and supplies. In 1799 Thompson’s explorations again took him through territory now within Alberta, this time with trading as well as surveying objectives—a measure of his rising importance within the company. He set out with a small group of Métis employees to locate, survey, and map the routes between North West Company posts. Along the way, Thompson met Charlotte Small, a Métis woman who became his wife and paddled his canoe alongside him. By 1807 Thompson had covered thousands of miles, through Alberta and over the great divide of the Rocky Mountains into British Columbia, where he established trade with the Kootenay Indians.
David Thompson’s method of surveying was based on what he learned from Philip Turnor: the determination of longitude through lunar observation. With three hours and a telescope in hand, he could establish Greenwich time by observing the moment of eclipse of one of the moons of Jupiter. Alternately, calculations could also be made in relation to the moon’s movement around the planet earth, which moves approximately 13º each day in relation to the fixed stars. By observing the angle between the moon and two fixed stars, Greenwich time – and hence longitude – could be calculated with reference to the astronomical tables in the Nautical Almanac.
Thompson made a track survey of his route using a magnetic compass for bearings and estimated distances between points. He took astronomical observations for latitude and longitude as a check, averaging out errors in the compass survey between the fixed points. “My instruments for practical astronomy, were a brass Sextant of ten inches radius, an achromatic telescope of high power for observing the satellites of Jupiter and other phenomena, one of the same construction for common use, Parallel glasses and quicksilver horizon for double altitudes (artificial horizons for using the sextant); Compass; Thermometer, and other requisite instruments, which I was in the constant practice of using in clear weather for observations on the Sun, Moon, Planets and Stars; to determine the positions of Rivers, Lakes, Mountains and other parts of the country I surveyed from Hudson Bay to the Pacific Ocean.” Thompson noted that John Dolland of London made his instruments. Dolland developed the achromatic lens after 1757, which was an improvement on the refracting lens in telescopes available to that time. Achromatic lenses produced better telescopic images than were previously possible, and revealed fainter objects, producing more accurate results.
Surveyors and historians alike have taken a good deal of interest in the level of accuracy that Thompson was able to achieve. By all accounts, the location of Thompson’s astronomical observation was usually within a mile or so of the true location. Historian William Stewart concluded that Thompson’s location of latitude was within a mile of correct, his longitude within two miles. Stewart noted that Thompson’s magnetic bearings contained “inconsistent and irregular errors” and that he recorded distances only to the nearest quarter mile. Thompson was unaware of problems associated with the earth’s magnetic field that would challenge surveyors who came after him. “It is a fact then,” Stewart warned, “ . . . that the latitudes and longitudes given in Thompson’s notes cannot, in general, be accepted as defining the position of old trading posts or other points of interest.” Thompson kept meteorological observations as well as field notes in his journals, recording the temperatures he encountered over a number of years. He was quite determined to know how cold it could be in the North-West. Thompson became suspicious of the accuracy of his first thermometers: “one of Spirits, and one Quicksilver; each divided to forty-two degrees below Zero, being seventy four degrees below freezing point.” The mercury froze, and it appeared to Thompson that, as the spirit approached the bulb, it seemed to take two or three degrees of cold to correspond with a drop of one degree registering on the thermometer. He wrote to Mr. Dolland in London requesting a thermometer divided “to upwards of one hundred degrees below zero.” By the winter of 1795, from halfway round the world, came “a thermometer of red coloured spirits of wine, divided to 110 degrees below zero, or 142 degrees below the freezing point.” Thompson tested it out at Bedford House on Reindeer Lake. On December 18, he confirmed his suspicions. The new thermometer read fifty-six degrees below zero while the older small spirit one would not descend beyond forty-one degrees below zero. Thompson experienced a good deal of difficulty establishing altitudes and requested a “mountain barometer” for his work in the Rocky Mountains. Twice a barometer arrived broken, so he gave up and resorted to the boiling water method—the lower the temperature of the boiling point, the greater the altitude—and making the necessary calculations, which proved to be quite inaccurate.
Thompson’s surveying career in western Canada concluded with travels through southeastern British Columbia. In 1811 he set out with a canoe party to find where the Columbia River led, and arrived at Astoria on the Pacific coast just weeks after the American Pacific Fur Company established a fort there. By 1812 Thompson was ready to retire from the North West Company, and he settled in Quebec. He then began work on a series of remarkable maps of the Canadian North-West based on his many surveys. In 1813, in completion of his contract with the North West Company, he delivered his Map of the North-West Territory of the Province of Canada from actual survey during the years 1792 to 1812. The map passed to the HBC on the merger of the two companies in 1821 and the rights to the map were sold to the Arrowsmith mapping firm in Britain. Arrrowsmith continued to incorporate Thompson’s work in the ongoing editions of its map of North America, which would not be supplanted until the Dominion Land Survey produced maps based on its surveys begun in the 1870s.
In 1816 David Thompson began a new phase of his career. He was appointed astronomer and surveyor by the British Foreign Office for the international boundary between Canada and the United States of America, established through the Treaty of Ghent at the end of the War of 1812. He worked on the section west from St. Regis on the St. Lawrence River. In 1824 his survey party reached the northwest shore of the Lake of the Woods, where Thompson left a monument to mark the location of the western termination point of the international boundary. Thompson then continued to perfect his maps. He provided a set for the British government in 1826 and then a final set in 1843.
In the early 1840s, Thompson used his maps to urge Britain to make a claim to the Oregon country where the North West Company bought out American interests at Fort Astoria, and which had become a bone of contention between Britain and America. The territorial dispute was eventually resolved in favour of the claims of the United States of America. A huge potential Canadian territory of three hundred thousand square miles was lost through the Oregon Treaty of 1846, when the forty-ninth parallel west from the Rocky Mountains to the Pacific was declared as the international boundary. This was a continuation of the forty-ninth parallel as the international boundary west from the Lake of the Woods to the Rocky Mountains, previously agreed on in 1818.
Although Thompson was well versed and involved in the political questions of territorial expansion of nineteenth-century Canada, he was not well known to his contemporaries. In 1843 a now impoverished David Thompson returned to his detailed survey journals of earlier days and sat down to write up an account of his travels and work. He died in 1857 and the manuscript languished unpublished for over half a century. David Thompson was virtually forgotten. Finally, in 1916, David Thompson’s Narrative of his Explorations in North America was published on the instigation of geologist Joseph Burr Tyrrell. Tyrrell, impressed by the accuracy of the map of the North-West still used by the Dominion Government of Canada in the 1880s, was curious to know more about Thompson. Hailed as a masterpiece of geographical writing, Thompson’s Narrative grabbed the imagination of men involved in the contemporary surveying of western Canada.
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