158 THE ARCTURUS ADVENTURE 



beach was faced by a sheer high wall. And in this 

 wall was a low-arched opening, as black within as 

 without. Not daring to hope that it would be any- 

 thing more than the merest recess worn by the 

 waves, we entered. To our delight ( for what could 

 be more satisfactory than an unexplored cave on 

 a desert island) it was a narrow passage that turned 

 sharply from the entrance and seemed to continue 

 for some distance. At first we could stand erect 

 and walk over a thick strewing of round pebbles, 

 but presently in growing darkness the roof came 

 down so low that we took to all fours and crept 

 along a tunnel, dimly lighted now and then 

 through fissures in the rock wall, opening at the 

 level of the sea outside. A flickering greenish light, 

 cast by the reflection of the sun on shallow water, 

 made our crepuscular worming even more eerie 

 than it would have seemed in total darkness. The 

 silken sound of the wavelets slipping over stones 

 inspired us simultaneously with the thought of the 

 tide, and in involuntary whispers we discovered 

 that we did not know whether it was rising or fall- 

 ing. Somewhat reassured by the recollection that 

 this was no Bay of Fundy or Mont St. Michel, and 

 that we should probably have sufficient warning to 

 escape from these confined quarters, we crawled 

 on. Presently the roof sloped up again, so that 

 we could thankfully rise from bruised knees. It 

 was very dark now, but stretching up and to both 

 sides, no walls or roof could be reached. We turned 

 round a slight angle and came suddenly into a 

 large chamber, where at the further end a mys- 



