230 Prof. B. Silliman junior on the 



for a year, and it would not be difficult to arrange such a series, if 

 the question was esteemed to possess sufficient scientific interest to 

 warrant the expense. If the cave had two openings at different 

 levels, the temperature would not be uniform, and there would be 

 two currents discernible. 



There is no exception to the purity of the air in the Mammoth 

 Cave, in none of the deep pits or domes is it possible to find any 

 accumulation of carbonic acid, or other noxious gases, respiration 

 and combustion are perfect in all parts which have yet been visited. 

 The waters of the springs and rivers within it are all limpid and 

 potable ; and the avenues, with few exceptions, are dry at all seasons. 

 I thought it very remarkable that, in all its vast extent, there should 

 be no sources of sulphuretted hydrogen and of carbonic acid.* 



The phenomena of life within the cave are comparatively few, but 

 interesting. There are several insects, the largest of which is a 

 sort of cricket with enormously long antennae. Of this insect, 

 numerous specimens will be found among the specimens sent to 

 Professor Agassiz. There are several species of Coleoptera, mostly 

 burrowing in the nitre earth. There are some small water-in- 

 sects also, which I suppose are Crustacean. Unfortunately three 

 vials containing numerous specimens of these insects were lost 

 with my valise from the stage coach, and I fear will not be re- 

 covered. Of the first, there are two species, one of which has 

 been described by Dr Wyman in the American Journal of Science, 

 and which is entirely eyeless ;t some ten or twelve specimens 

 of the species were obtained. The second species of fish is not 

 colourless like the first, and it has external eyes, which, however, 

 are found to be quite blind. | The craw fish or small Crustacea in- 

 habiting the rivers with the fish are also eyeless and uncoloured, 

 but the larger eyed and coloured craw fish which are abundant with- 

 out the cave, are also common at some seasons in the subterranean 

 rivers, and so also it is said the fish of Green River are to be found 

 in times of flood in the rivers of the cave. Among the collections 

 are some of the larger eyed craw fish which were caught by us in 

 the cave. The only mammal except the bats observed in the cave 

 is a rat, which is very abundant, judging from the tracks which they 

 make, but so shy and secluded in their habits, that they are seldom 

 seen. We caught two of them, and fortunately male and female. 



The chief points of diiference from the common rat in external 

 characters, are in the colour, which is bluish ; the feet, and belly, 

 and throat, white ; the coat which is of soft fur, and the tail also 



* Near " Mary's Bower," there is a spring of bitter water, evidently con- 

 taining sulphate of magnesia, which salt is also abundantly found in some parts 

 of the cave. 



t See also Proceedings Brit. Soc. Nat. Hist., 1850, p. 349. 



X For a list of the animals found in the cave, as mentioned by Prof. Agassiz, 

 see this volume, p. 127. 



