Iron ores, salt and sandstones . d 2 millimeters in size is fed in thepath of specimen to act as an abrasive agent. At theend of 1,000 revolutions of the disc, the sample is taken outand its loss in weight is used in determining the hardnessof the specimen by the following formula: W where H is the hardness, and W the loss in grams per 1,000revolutions. The following maximum and minimum results of testsmade by the Bureau of Good Roads are given for illustra-tion : 3S tested. Kind of rock. HardnessMax. Min. 246 Limestone 62 Sandstone 84 Granite The hardness of stone
Iron ores, salt and sandstones . d 2 millimeters in size is fed in thepath of specimen to act as an abrasive agent. At theend of 1,000 revolutions of the disc, the sample is taken outand its loss in weight is used in determining the hardnessof the specimen by the following formula: W where H is the hardness, and W the loss in grams per 1,000revolutions. The following maximum and minimum results of testsmade by the Bureau of Good Roads are given for illustra-tion : 3S tested. Kind of rock. HardnessMax. Min. 246 Limestone 62 Sandstone 84 Granite The hardness of stone in its relation to resistance towear or abrasion is an important quality to be considered inthe use for steps, and walks. Soft stone soon wears, be-coming uneven and lasts but a short time. A method of testing the abrasion or per cent, of wear onroad materials has been in use in Paris since 1878, and fora number of years in this country. The following descrip-tion of the method is taken from the Maryland GeologicalSurvey Plate XV.—A.—Marietta Sandstone at the Cleveland GrindstoneQuarry, Briscoe, Wood County
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Keywords: ., bookcentury1900, bookdecade1900, bookpublishermo, booksubjectsalt
