Bulletin . DESCKIPTIONS OF VARIOUS TYPES OF STOPPINGS. 21 CONCRETE STOPPINGS. In many mines, concrete is the most suitable material for use inthe construction of efficient stoppings in the crosscuts between mainair passageways. Concrete stoppings may be constructed at reason-able first cost, they have low maintenance charges, they are durable,

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Keywords: ., bookcentury1900, bookdecade1910, booksubjectminesandmineralresou