opening the swallet, where a tiny brook ran away through small crevices in a Limestone ravine. A far-extending cave was thus disclosed, full of intricate ramifications, that explain in a graphic manner how new galleries are formed and old ones left dry and deserted, as the result of floods and partial chokes. We have, in the longest route discovered in this complicated system, reached a distance of 2000 feet from the entrance and a depth below the surface of 500 feet. At this point no absolutely impassable barrier has been met with. There is reason to hope that we may still advance farther into the mysterious region between it and Wookey Hole. But the formidable difficulties of the journey hither have set a limit to endurance. Hundreds of feet of creeping through steep, narrow, and contorted passages, compared with which a series of drain-pipes would afford luxurious travelling; perpendicular drops of 50 and 90 feet, with no convenient ledges at the top for letting men down; and, in addition, the necessity of transporting great quantities of tackle to the bitter end of it, have made a twelve hours' day underground as much as we could stand. The difficulty may perhaps be got over by means of a subterranean bivouac. Unfortunately, it would not do to leave the apparatus in position for long beforehand, as it would deteriorate so rapidly. In Wookey Hole itself, we have not yet succeeded in reaching a farther distance than 600 feet from the cave mouth; there a submerged tunnel has stood in the way. But Mr. Balch has thoroughly explored the upper passages that honeycomb the rock above the known caves; he has discovered a number of promising galleries, which are being slowly cleared of débris; and, among them, a series of the most beautiful incrusted grottoes in Britain. A season of drought may reveal an opening up the river-course.