 | J.D. Dana - 1855 - 440 Seiten
...fine grained argillaceous variety, commonly of a dark dull blue or bluish-black color, or somewhat purplish. To be a good material for roofing, it should...thing that can undergo decomposition on exposure. In the United States, a good material is obtained in Maine at Barnard, Piscataquies, Kennebec, Bingham... | |
 | Tennessee. Geological Survey, James Merrill Safford - 1856 - 178 Seiten
...for roofing is generally of a dark-bluish or purplish color. The color is not, however, important. " To be a good material for roofing, it should split...immersion for a while in water. It should also be free from pyrites, and every thing that can undergo decomposition on exposure."* 273. 4th. Flagging-Stones.—When... | |
 | James Dwight Dana - 1859 - 236 Seiten
...fine grained argillaceous variety, commonly of a dark dull blue or bluish-black colour, or somewhat purplish, To be a good material for roofing, it should...in water. It should also be pure from pyrites and everything that can undergo decomposition on exposure. Roofing slates occur in England, in Cornwall,... | |
 | James Merrill Safford - 1869 - 604 Seiten
...for roofing is generally of a dark-bluish or purplish color. The color is not, however, important. "To be a good material for roofing, it should split...immersion for a while in water. It should also be free from pyrites, and every thing that can undergo decomposition on exposure."* FLAGSTONES. (17.)... | |
 | James Merrill Safford - 1869 - 604 Seiten
...for roofing is generally of a dark-bluish or purplish color. The color is not, however, important. "To be a good material for roofing, it should split...immersion for a while in water. It should also be free from pyrites, and every thing that can undergo decomposition on exposure.''* FLAGSTONES. (17.)... | |
 | James Merrill Safford - 1869 - 598 Seiten
...roofing is generally pf, a dark-bluish or purplish color. The color is not, however, important. u Tp.be a good material for roofing, it should split easily...may be tested by weighing, after .immersion; for a wjnle in wa,t@r. It should also be free from pyrites, and every thing that can undergo decomposition... | |
 | Junius Brutus Wheeler - 1876 - 504 Seiten
...is a .stratified rock of great hardness and density, commonly of a dark dull bine or purplish color. To be a good material for roofing, it should split...slates, and admit of being pierced for nails without being fractured. It should be free from everything that can on exposure undergo decomposition. The... | |
 | Junius Brutus Wheeler - 1876 - 502 Seiten
...is a stratified rock of great hardness and density, commonly of a dark dull blue or purplish color. To be a good material for roofing, it should split...slates, and admit of being pierced for nails without being fractured. It should be free from everything that can on exposure undergo decomposition. The... | |
 | Junius Brutus Wheeler - 1876 - 504 Seiten
...is a stratified rock of great hardness and density, commonly of a dark dull blue or purplish color. To be a good material for roofing, it should split...slates, and admit of being pierced for nails without being fractured. It should be free from everything that can on exposure undergo decomposition. The... | |
 | Junius Brutus Wheeler - 1876 - 506 Seiten
...is a stratified rock of great hardness and density, commonly of a dark dull blue or purplish color. To be a good material for roofing, it should split...slates, and admit of being pierced for nails without being fractured. It should be free from everything that can on exposure undergo decomposition. The... | |
| |
To be a good material for roofing, it should split easily into even slates, and admit of being pierced for nails without fracturing, Moreover, it should not be absorbent of water, either by the surface or edges, which may be tested by weighing, after... 