David Thompson was born in London, England, on April 30, 1770. His parents were Welsh, and of little means. His father died when he was two, and at the tender age of seven, he was enrolled by his mother in the historic 'Grey Coat' charity school near Westminster Abbey.
Having shown an aptitude for mathematics, his education was oriented towards preparing him for life as a midshipman in the Royal Navy. His studies included algebra, trigonometry, geography, and navigation using 'practical astronomy'.
Over the years, the Hudson's Bay Company (HBC) made periodic requests to the school for students to be apprenticed to the North American fur trade. Many of these students would later receive training from Philip Turnor, the HBC's first chief surveyor. Among these pupils were Joseph Hansom, George Hudson, John Hodgson, and George Donald.
As Thompson neared the end of his education, the Hudson's Bay Company asked for four more apprentices. Only two were eligible at that time ; one of them was the fourteen-year-old David Thompson. In May 1784, he set sail for Hudson's Bay aboard the Prince Rupert. He never saw his mother or England again.
It is not known what duties he may have performed during the voyage, but he owned a Hadley's quadrant when he left England, presented to him when he finished school. The Hadley's quadrant was a double-mirrored navigational instrument which could measure angles up to ninety degrees. In 1785, he had to leave this quadrant behind at Churchill when he was transferred to York Factory, expecting it to be forwarded to him eventually. He apparently never used it again, since in 1790 it was requisitioned by Joseph Colen for use aboard the York Factory sloop. Thompson's early work in America did not include surveying. He later wrote '[in 1789] I regained my mathematical education...', suggesting he had become quite rusty (Glover, 55).
In 1786 Thompson journeyed inland along the North Saskatchewan River to Manchester House (northwest of today's North Battleford), where he spent the winter. In 1787 he traveled across country to spend the winter with a band of Peigans encamped along the Bow River in the Calgary area, returning to Manchester House in the spring of 1788. Thompson did not make surveys of these travels.
On December 23, 1788, about a mile from Manchester House, the eighteen-year-old Thompson fell down a bank and broke his leg. The break was serious, and the injury life-threatening. William Tomison, who ran Manchester House at that time, bound the leg, and a 24 hour vigil was kept for three weeks before it was deemed safe for Thompson to be alone at night.
Thompson's condition remained grave. Four months after the accident, Tomison noted in his journal that he was afraid Thompson could die. On May 1, 1789 he wrote 'David Thompson's leg I am afraid will turn out to be a mortification as the joint of his ancle has never lowered of the swelling' (Glover, xxiii).
Tomison decided to send Thompson to York Factory that same spring, presumably in an attempt to remove Thompson to better medical care. However, the brigade was forced to leave him at Cumberland House, about two weeks' travel dowriver from Manchester House. It was another two months before Thompson was again able to sit up in a chair (August 10, 1789). By the end of August, he was taking his first feeble steps with the help of crutches. It took him a full year to recover, but he would limp for the rest of his life.
It was at Cumberland House that Thompson's life would take a new path. In October, 1789, Philip Turnor arrived to plan a surveying expedition to the Athabasca country with the man in charge of Cumberland House, Malchom Ross. The study group included Turnor, Ross, George Hudson, and the young Peter Fidler. The invalid Thompson was invited to join in Turnor's lessons. He later wrote with remembered pride & pleasure that 'during the winter [I] became his only assistant and thus learned practical astronomy under an excellent master of the science' (Glover, 55).
By 1789, Philip Turnor had been the HBC's official surveyor for over ten years. His work had been included in the nautical almanacs, which seems to have impressed and possibly inspired Thompson. Turnor may also have influenced another great explorer. He bumped into Alexander Mackenzie shortly after the North West Company (NWC) explorer returned from his journey to the Arctic Ocean, and it seems that Turnor's skeptical reception caused Mackenzie to return to England and brush up on his navigational skills before he made his journey to the Pacific (Lamb, 18-19).
On February 1, 1790, Thompson recorded his first navigational measurement. It was a lunar distance measurement for the longitude of Cumberland House. Over the next four months, Thompson made thirty-four such measurements, and six observations for latitude. His final results placed Cumberland House at latitude 53° 56' 44" N by 102° 13' W. This position is only 1.5 miles south and 2.7 miles east of the modern value.
In the letter to the London Committee of the HBC that year, Philip Turnor wrote
'I have inserted some Observations which were made and worked by Your Honors' unfortunate apprentice, David Thompson. I am fully convinced they are genuine, and should he ever recover his strength far enough to be capable of undertaking expeditions I think Your Honors may rely on his reports of the situation of any place he may visit.' (Nisbet, 35)
During his navigational training that winter, Thompson became blind in his right eye, probably due to observing the sun without proper eye protection. (See 'A Theory on the Cause of David Thompson's Blindness', Northwest Journal Vol. II, pp. 23-26) In the spring of 1790, Thompson was still too weak to accompany Ross, Turnor & Fidler on the Athabasca journey. Instead, Thompson was ordered to accompany a brigade to York Factory. They departed Cumberland House on June 9. He surveyed this route as he traveled, using a sextant and watch borrowed from Philip Turnor. After a short stay at York Factory, Thompson returned to spend the winter at Cumberland House, where he returned Turnor's instruments.
It was in 1790 that York's Governor, Joseph Colen, requisitioned Thompson's quadrant, possibly after discussing it with Thompson. By then, Thompson would have known that a quadrant was an impractical instrument for land navigation since it did not measure sufficiently large angles.
Thompson's apprenticeship was due to end in 1791. HBC apprentices were usually given a suit of clothes when they completed their apprenticeship. Thompson appealed to the company to provide him with surveying instruments instead, and to charge any excess against his future pay. That August, Thompson ordered 'a Brass Sextant of not less than 10 Inches Radius, the Index Glass, part blacked, part Quicksilvered, with two pair of Red, and one pair of Green Shades, the Shades to be fixed to the Instrument. (as the shades to slide in, are frequently inconvenient when their clouds are flying).' from Peter Dolland, of St. Paul's Churchyard, London (Smyth, 5). He also ordered an artificial horizon, a device that land navigators use to replace a sea horizon, which was described as 'a pair of Parallel Glasses, 3½ Inches by 3½ Inches of the foldings to have Brass Hinges, in a neat Shagreen Case.' (Smyth, 6).
The following year, Thompson received the fine sextant he had requested, which was accurate to 15 seconds of arc. He also received the artificial horizon and a new suit of clothes. Everything was at the Company's expense.
In the summer of 1791, Thompson again traveled to York Factory, where he spent the winter. (This is presumably where he took possession of his new instruments.)
That September, he ordered 'a brass compass as per boats, cut shoal for taking azimuths for variation', 'a Fahrenheit's Thermometer for correcting the refraction on the celestial Bodies, which is very erronious in the Winter occasioned by the great density of the air,' various drawing instruments, and the latest two volume set of Robertson's Elements of Navigation, the standard text of the time (Smyth, 6,7). All of these items arrived during the summer of 1792. During this time, Thompson also received two watches, but the type and maker are unknown.
In September 1792, equipped with his new instruments, Thompson left York Factory under orders to find a newer, shorter route to the fur-rich Athabasca country by way of the Churchill River. Joseph Colen, the governor of York Factory, had hoped Thompson would be able to winter at Reindeer Lake, but instead Thompson spent the winter at a trading house that he and his men built at Sipiwesk Lake. There they were often short of supplies.
