but we did let one large notebook go. If worst came to worst, we could resort to rock chipping—and, of course, it would be possible, even in case of really lost direction, to work up to full daylight by one channel or another if granted sufficient time for plentiful trial and error. So, at last, we set off eagerly in the indicated direction of the nearest tunnel.
According to the carvings from which we had made our map, the desired tunnel mouth could not be much more than a quarter of a mile from where we stood; the intervening space showing solid-looking buildings quite likely to be penetrable still at a subglacial level. The opening itself would be in the basement—on the angle nearest the foothills—of a vast five-pointed structure of evidently public and perhaps ceremonial nature, which we tried to identify from our aerial survey of the ruins.
No such structure came to our minds as we recalled our flight, hence we concluded that its upper parts had been greatly damaged, or that it had been totally shattered in an ice rift we had noticed. In the latter case the tunnel would probably turn out to be choked, so that we would have to try the next nearest one—the one less than a mile to the north.
The intervening river course prevented our trying any of the more southern tunnels on this trip; and indeed, if both of the neighboring ones were choked it was doubtful whether our batteries would warrant an attempt on the next northerly one—about a mile beyond our second choice.
As we threaded our dim way through the labyrinth with the aid of map and compass—traversing rooms and corridors in every stage of ruin or preservation, clambering up ramps, crossing upper floors and bridges and clambering down again, encountering choked doorways and piles of debris, hastening now and then along finely preserved and uncannily immaculate stretches, taking false leads and retracing our way (in such cases removing the blind paper trail we had left), and once in a while