To make a geological map, you need a topographical map as a base. In the 19th century, however, Canada’s topography was mostly uncharted. This meant early Geological Survey of Canada geologists had the extra work of making them. As William Logan noted, “In older countries the labours of topographers and geographers have preceded those of the geologist.” This added task slowed the portrayal of Canada’s geology and the discovery of its resources, but produced excellent maps and ultimately led to the establishment of systematic topographical mapping by surveyors.
These brass instruments were used on the prairies in the 19th century to plot the fixed locations on Earth’s surface needed to make the maps. The solar compass (top) uses the sun’s direction to locate positions. It was used from the mid-19th century until late-20th century, yielding very accurate results. The Wye level (bottom), with its telescope and magnetic north compass, was used to determine precise elevation differences and establish benchmarks.
Using these and other instruments for measuring distances, the early Survey geologists triangulated their way across the landscape – an arduous process compared to the convenience of today’s satellite-based global positioning systems.
Category: Maps
Decade: 1870s
References
The Surveyors Basic Tools: www.surveyhistory.org/the_surveyor's_basic_tools.htm
