One of the implications of other roofers entering the slating business was that the importance of experience passed-down from one roof company to another was reduced while the technical direction of trade journals and building product suppliers, that is the slate quarries, was correspondingly enhanced. This evolution in the slating trade meant that Canadian slating practice, which started with British and some French influences, ended with almost exclusive dependence on the methodology of its American suppliers. At the outset of roofing slate production and use in Canada and the United States, both countries showed a strong and natural reliance on British know-how in slate extraction and application. Welsh quarry men initially operated the Quebec, Vermont, New York and Pennsylvania slate quarries. The architects and tradesmen of the 1860-80s period had direct experience of homeland work and these techniques were popularized both by example and the North American publication and distribution of British builders’ encyclopedias by Peter Nicholson, Joseph Gwilt, and J.C. Loudon.5 Canadian and American professional periodicals also printed extracts on slating from the National Builder and Planat’s Encyclope’die de’architecture etde la construction. By the late 1890s, however, American-generated advice on slating became increasingly evident in the Canadian Architect and Builder and was reinforced by the guides and leaflets produced by the American slate industry, the source of most slate used in Canada after 1900.