accessible, and thoroughly charming spot, has escaped their attention altogether, with a marvelous store of attractions which are both extremely old and wholly new.

Each of these regions has a peculiar geological history not repeated in any other portions of the earth's surface: each is blessed with its own peculiar style of beautiful scenery: and each vies with the other and all the world besides for the supremacy of its truly wonderful caves. Yet it should be well understood that the claims are not based on an unworthy spirit of rivalry, nor any desire to deny the greatness and beauty of already famous members of the Cave family. It is simply an announcement that the family is much larger than has been generally supposed, and the more recently presented members worthy of the full measure of distinguished honors.

The geological authorities of both states have for many years mentioned the beauty and importance of these regions, and urged their claims to public attention, but have been prevented, by the pressure of other duties, from giving to the caves such careful study and full reports as they deserve, as it would have been a pleasure to give, and as has been possible in states of less extent where the general work of the department is more advanced, and the volume of tourist travel created an early demand for scientific explanation.

Without any great difficulty we can understand the process of cave excavation by the action of percolating acidulated water on the limestone, and its subsequent removal as the volume of surface drainage diverted to the new channel gradually increased. But it is not so easy to offer a reason for the varied forms with which the caves are afterwards decorated. Why is it the charmed waters do not leave the evidence of their slow passage only in plain surfaces of varying widths, and the stalactites and stalagmites whose formation we can readily account for? And why do not the deposits take the same forms in all caves with only such variations as would naturally result from differences in topography? The law is written, but in unfamiliar characters that render our reading slow and uncertain. Yet it is conspicuously noticeable that those caves showing the most delicately fragile and wonderfully varied forms of decoration are those traversed by the most sweeping and changeable, or even reversible, currents of air; which might lead to the conclusion that the moisture is sprayed or converted into a light, misty vapor, and then deposited in exactly the same manner as the beautiful frost-work at Niagara: the direction and force of the current determining the location of the frail deposits.

Since the largest and most important caves occur in limestone, a little special attention to the cause of their occurrence there may serve to show that although speleology has only recently received its name and been elevated to the rank of a separate and independent science, it is one of the earth's ancient institutions.

Our geologists, who have unearthed many secrets not dreamed of even in Humboldt's "good phylosopy," have settled the question of how the different kinds of caves were formed, according to the character of rocks they are in, or their location and depth, and the natural agencies to whose action they show signs of having been subjected.

Dr. H. C. Hovey, in his "Celebrated American Caverns," says: "In visiting caves of large extent, one is at first inclined to regard the long halls, huge rifts, deep pits and lofty domes, as evidences of great convulsions of nature, whereby the earth has been violently rent asunder. But, while mechanical forces have had their share in the work, as has been shown, the main agent in every case has been the comparatively gentle, invisible gas known as carbonic acid. This is generated by the decay of animal and vegetable substances, and is to a considerable degree soluble in water. Under ordinary circumstances one measure of water will absorb one measure of carbonic acid; and the eye will detect no difference in its appearance. Under pressure the power of absorption is rapidly increased, until the water thus surcharged has an acid taste, and effervesces on flowing from the earth, as in Saratoga water.

"Rain-water, falling amid leaves and grass, and sinking into the soil, absorbs large quantities of carbonic acid. On reaching the underlying limestone, the latter is instantly attacked by the acidulated water in which it is dissolved and carried away.

"It is agreed among geologists, amazing as the statement may seem, that the immense caverns of Virginia, Kentucky and Indiana, including Mammoth Cave itself (the largest of all), were eaten out of the solid mass of limestone by the slow, patient, but irresistible action of acidulated water."

Professor N. S. Shaler says: "The existence of deep caverns is a sign that the region has long been above the sea."

Through the kindness of Professor C. J. Norwood, Chief Inspector and Curator of the Geological Department of Kentucky, it is possible to quote the first official report made on the caves of that state and published in 1856, in Volume I., Kentucky Geological Survey Reports. Dr. Norwood says: "Referring to the 'Subcarboniferous Limestone' (now known as the St. Louis group of the Mississippian series), Dr. Owen says: 'The southern belt of this formation is wonderfully cavernous, especially in its upper beds, which being more argillaceous, and impregnated with earths and alkalies, are disposed to produce salts, which oozing through the pores of the stone effloresce on its surface, and thus tend to disintegrate and scale off, independent of the solvent effects of the carbonated water. Beneath overhanging ledges of limestone, quantities of fine earthy rubbish can be seen, weathered off from such causes. In these I have detected sulphate of lime, sulphate of magnesia, nitrate of lime, and occasionally sulphate of soda. The tendency which some calcareous rocks have to produce nitrate of lime is, probably, one of the greatest causes of disintegration.'"

"Most extensive subterranean areas thus have been excavated or undermined in Edmonson, Hart, Grayson, Butler, Logan, Todd, Christian and Trig. In the vicinity of Green River, in the first of these counties, the known avenues of the Mammoth Cave amount to two hundred and twenty-three, the united length of the whole being estimated, by those best acquainted with the Cave, at one hundred and fifty miles; say that the average width and height of these passages amount to seven yards each way, which is perhaps near the truth; this would give upwards of twelve million cubic yards of cavernous space which has been excavated through the agency of calcareous waters and atmospheric vicissitudes."

Page 169: "On the south side of Green River the platform of limestone forming the descent into Mammoth Cave is two hundred and thirty-two feet above Green River."

"The entrance to the cave, being thirty-eight feet lower than this bed of limestone, is one hundred and ninety-four feet above Green River. In the above two hundred and thirty-two feet there are several heavy masses of sandstone, viz.: at one hundred and twenty-five, one hundred and forty-five, one hundred and fifty, one hundred and sixty and two hundred and fifteen feet, but it is probable that most of these have tumbled from higher positions in the hill, as no alterations of sandstone have been observed at these levels in the cave. From an elevation of from two hundred and forty to two hundred and fifty feet, the prevalent rock is sandstone without pebbles, which can be seen extending up to three hundred and twelve feet to the foundation of the Cave Hotel. The united thickness of the limestone beds on this part of Green River, is about two hundred and