Contained within the 3rd Edition (1957) of the Atlas of Canada is a map that shows the electrical generating network in Western Canada circa 1954. Generating plants are shown as either developed waterpower sites (in other words, hydro plants), or as fuel electric plants (thermal plants). The plants are portrayed on the basis of their capacity, measured in horsepower. The map also shows transmission lines of 60 000 volts or higher. Note that in a number of cases, cartographic considerations require that two or more side-by-side transmission lines be shown as a single line on the map. An interesting feature of the map is that it shows the location of potential hydro sites. Each of these is shown by a proportional circle measuring its potential capacity. There is an inset with two pie charts showing the distribution of net generating capability of facilities in 1954. Net Generating Capability estimates are based on actual operating experience assuming all equipment is available at the time of annual peak demand. These estimates make no allowance for the effect of unfavourable water or ice conditions. However, the estimates do allow for needs of the station and so deduct station services.