... Report on the building and ornamental stones of Canada, vol. I-V (1912)
Parks, W. A. (William Arthur), 1868-1936, Canada. Mines Branch · Ottawa : Government printing bureau · leaf 162
y. The surface, after being divestedof debris and soil, is at once attacked by channeling machines and the excava-tion carried down vertically 4 to 8 feet. The opening is then enlargedby directing the channels outwards on all four sides at an angle of about 25° 99 from the vertical. This is… … Fig. 6. Method of opening a quarry in the form of truncated pyramids connectedby tunnel. At the base of this opening, on the two sides facing the strike of the beds,tunnels are driven through the poorer upper material, by the careful use ofmild explosives. These tunnels may extend along the strike…
Building stones
Internet Archive · California Digital Library · Public Domain Mark 1.0. Free to use for anything.
