They walked for two hours without running into any tunnels branching off from the main one.
The Alleghany Plateau consists of nearly horizontal beds of limestone, sandstone and shales, including important seams of coal; inclines slightly toward the north-west, and is intricately dissected by extensively branching streams into a maze of narrow canyons and steep-sided hills.
Similarly the giant cells are produced at their periphery into a number of branching processes which bear similar end-organs on their surface and in some cases terminate in them.
To overcome these difficulties the " branching multiple " was introduced.
With the " branching multiple " the " selfrestoring drop " was introduced.