text:  The subterranean passages under the Rock provided the sole available office space , and in them was located the signal equipment by which we expected to keep in touch with the commanders of the three assault forces . The eternal darkness of the tunnels was here and there partially pierced by feeble electric bulbs . <unk> , cold air in block @-@ long passages was heavy with stagnation and did not noticeably respond to the clattering efforts of electric fans . Through the arched ceilings came a constant drip , drip , drip of surface water that faithfully but drearily ticked off the seconds of the interminable , almost unendurable , wait which always occurs between completion of a military plan and the moment action begins . 
  