8 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



■white and black limestones, like snow-clouds drifting in a wintery sky. A rise of only 5 feet would completely 

 cover this sandy walk, and this is its Condition for fro'm four to eight months in every year. The streams are usually 

 low in summer, when there are also the most visitors ; a fortunate coincidence. 



The connection of the cave rivers with Green Eiver has been demonstrated by the simple experiment of throwing 

 chaff upon them, which comes to the surface in the upper and lower big springs — deep, bubbling pools, lying half a 

 mile apart, under cliffs bristling with hemlock and pine. When these pools are submerged by a freshet in Green 

 Eiver the streams in the cave are united into a continuous body of water. The rise is augmented by the torrents 

 emptied down through the sink-holes, and sometimes is so great as to touch the iron railing above the Dead Sea. 



The subsidence of so vast a body of water, although for some reason less rapid than of streams without, must be 

 with powerful suction, causing eddies and whirlpools. In order to save from destruction at such times the uncouth 

 little fleet, built' of planks and timbers, every piece of which was brought in through passes we had traversed with 

 difficulty empty-handed, the boats are securely fastened, when not in use, by long ropes of twisted grape-vines, that 

 let them swim with the flood. 



A further account of the water-system and its inhabitants by Mr. H. G-. Hubbard is copied 

 from the American Entomologist, iii., 1880. 



With this avenue the water system of the cave communicates at several points, forming pools known as Lake 

 Lethe, the Eiver Styx, and similar plutonic appellations. The floor of the avenue is of fine sand, and at high tide the 

 water rises from 40 to 50 feet, filling it nearly to the roof. When the Green Eiver rises above a certain height a sub- 

 marine connection is established between its waters and those of the so-called river of the cave, which then rises and 

 falls with the water outside. At the time of our visit the flood was at its usual summer ebb, and these Stygian pools 

 lay in motionless tranquillity, their crystal depths undimmed and their glassy surfaces unruffled by current or eddy. 



Arrived at the point where the Eiver Styx crosses the gallery, we found Charon's boat drawn up upon the sand, 

 and, depositing our burdens, we began a search alongshore for blind fish and crawfish. The forms of several were 

 soon seen floating like white phantoms in the almost invisible water, and we captured with an insect-net several 

 small specimens of both species of blind- fish, Amblyopsis and Typhlichthys, which resemble each other closely, but want 

 the ventral fin in the latter genus. We took also good specimens of the cave crawfish ( Cambarus pellucidus, Tellk.), and, 

 in addition, a gigantic female of Cambarus bartoni, the common crawfish of the Green Eiver, but which has quite often 

 been found in the cave waters. A very unexpected find however was a common frog. He was resting upon the sand 

 not far from the water, and was somewhat emaciated and apparently much discouraged. A fish with large and per- 

 fect eyes, probably a darter, showed itself in one of the large pools. It remained for some time motionless at the sur- 

 face of the water within easy reach, but "Pete" missed it with the net, and it vanished in a twinkling, not to appear 

 again. A single Anophthalmus, found running on the sand, was the only insect, except crickets, seen here. When, 

 therefore, the party arrived we decided to accompany them farther. We embarked 'with them in one of the boats, and 

 leaving the gallery on our left, pushed under a low, wide arch, and floated for half a mile in an aqueduct, like a mam- 

 moth sewer, over water 30 or 40 feet deep. The guides, standing up in the bows, propelled the boats by pushing 

 with their paddles against the low roof. At its end the river sinks beneath the wall of rock, but another great gal- 

 lery opens here at the side, and another system of halls and avenues begins, the farthest point of which, and the end 

 of the Long Eoute, is still a walk of 6 miles from the river. 



An avenue extends from Cascade Hall to Eoaring Eiver; a succession of shallow ripples and deep basins, 

 navigated by a canoe. 



During the time I was at Mammoth Cave, the last of April, 1874, the water was very high, and 

 it was impossible to collect either crayfish or blind-fish. It had been above the stairs leading down 

 to the Dead Sea. The water here rises 70 feet. Above the highest water-mark near the Dead Sea, 

 and again in River Hall, I found three species of Helix ; the shells were dead, and of course must 

 have been brought in from out of doors. On the damp sand banks above the water were the little 

 holes or burrows of Anophthalmus, showing that they had retained the burrowing habits of their 

 ancestors of the upper world of light. The Adelops was also frequent. Anthrobia and its egg- 

 sacks or cocoons, Phalangodes armata, Chthonius paclcardii, Campodea coolcei lived under stones in 

 the drier places, and Hadenoecus subterraneus, or the cave cricket, clung to the walls. In the 

 mud were the larvae of Chironomus and Sciara. 



That there is a free communication between the River Styx and the Green River, or streams 

 outside of the cave, is proved by the presence of large snail shells, besides the occurrence of speci- 

 mens of Cambarus bartoni, and of a frog, as well as eyed fishes said to be common in the waters 

 of the region overhead. 



Temperature of Mammoth Cave. — This has been elaborated by Mr. Hovey more completely 

 than by any one else. The mean temperature of the Carniolan caves is said by Dr. Joseph* to be 



* Dr. Joseph remarks that the temperature of the Carniolan caves depends on the equal pressure of the air, equal 

 elevation above the sea-level, and equal distance from the entrance. The air in those outer chambers which are 

 reached by daylight is somewhat lower in summer and higher in winter than the inner chambers. The air in the 



