Interpreting the Collections
The Power of Visualization: Geological Maps
"Geological Map of Canada and the Adjacent Regions Including Part of Other British Provinces and of the United States," by William Logan and James Hall, 1869
Maps were the most striking product of nineteenth-century geological surveys.
Geological surveys coloured the land according to 30 or more divisions, promising
a completeness and certainty of knowledge that was instantly comprehensible. A
bureaucrat, investor, or settler had only to glance at a geological map to read
the economic future of any piece of land: was it suitable for agriculture, forestry, quarrying, or mining, or was it merely useless waste that needed to be avoided? Corresponding to its immense usefulness, however, constructing an accurate geological map was immensely difficult to do.
William Logan in his lab in Montreal
In Britain, geologists simply coloured existing trigonometrically surveyed
maps. Nineteenth-century Canada had no such mapping program, however, so a major
part of Logan's task was uniting and reconciling the many partial maps available
to him. His geological map of British North America was exhibited at Paris in
1855, and published in a small format, but he was dissatisfied with its lack of
geographical precision and later used telegraphic time signals to improve the
longitude determinations of Canadian cities. The improved map was published on
a very small scale (125 miles to the inch) in the 1865 Atlas, and the large
version (25 miles to the inch), with thousands of place names added, appeared
in 1869 (but was dated 1866). By British standards, this map was still very general, and useful mainly for the overall impression it gave of Canada and the surrounding territories.
Geological maps had only been invented around 1800 and were still an evolving
technology in Logan's era. Colour printing was a particular challenge: by mid-century, small maps could be produced by chromolithography, but large maps still had to be hand-coloured. Although Logan employed a British colour scheme for the 1865 map, it did not provide sufficient contrast between adjacent formations and was not used on the large map of 1869. Perhaps the most obvious feature of Canadian geology revealed by the map was the dominance of the enormous region of Laurentian rocks (later known as the Canadian Shield), covering much of Ontario and Quebec beyond settled areas, as well as the northwestern territories into which Canada would soon expand.