Show A Ticklish Bit of Tunneling A it v very Interesting bit of tunneling was as rece rec recently ly done on n the Fourteenth street tube under the river East New NewY Y York The heading beading was being run In rock rock and at one point test holes showed showed show ed a av thickness of only eight Inches of sound dry rock above the line along which the top of the tunnel was to run As the tunnel was being driven without the the- use of compressed air it was decided to drop the upper headIng head head- Ing lag four feet until this thin cover of rock was passed The cast Iron lining was set In place at at- each side of this section and the rock was removed very carefully by using using-a a great many holes each loaded with about one- one eighth of a n stick st o of dynamite As each each bit of rock w was s r removed moved the arch of the tunnel lining was set In place By this means the dangerous section vas was tunneled without br Breaking g- g through gh the thin shell |