Casteret's seventh book on speleology flashes both go ahead signals and danger signals for underground exploration. On the one hand the teacher in him warns ""make haste slowly""- and with forethought. On the other, a return to a cave he'd discovered twenty four years earlier inspires description of the joys of pot- holing to the daughters accompanying him. He launches into a chilling martyrology which points out in its victims the perils of speleology, whether from carelessness or ignorance on the part of the explorer or from natural dangers, the most common one-flooding. Hair-raising episodes abound:- the drowning of six entymologists at Blamont in the Pyrenees, siphon misadventures, a honeymooners' wedding night spent desperately lost underground, and so on. Plenty here to tell and plenty to teach! Those who read and enjoyed Tazieff's Caves of Adventure (also set in the Pyrenees) will certainly appreciate this wary approach to underground delights and perils.