le in sandstone, marble, slate, etc., increase may reasonably be estimated at 2,500,000. Of course if fifteen feet per hour is easily bored. this canrot come from the anthracite mines. Our bituminous These facts, together with the simplicity and solidity of coal-fields must furnish the largest… … It may, or can take SINGLE DRILL TUNNEL MACHINE, the place of anthra- OPEN CUT OR QUARRY DRILL. cite in almost, if not every case, where fuel is required, but repairs incidental to percussion driJling, place these machines out the release gear, H, by sliding it up the feed-shaft, F, to anthracite…
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