This was the end of the cave so far as the brewery was concerned. It terminated here with a masonry wall. To see where it went beyond, Mr. Hess had the wall broken down with a hydraulic jack and was disconcerted to find that although the cave does, indeed, continue, it was almost completely filled by a deposit of stiff, wet clay. This made it impassable for anything much larger than a rat. He had workmen dig a narrow passage in the clay, following the ancient channel of the cave. Within 20 feet from the wall it turned to the left, northward, and had, at the time of our visit, been followed in that direction for some 200 feet farther, with no sign of ending, or of coming out to the surface, or of joining another, adjacent old brewery cave (the Minnehaha Cave) with which Hess hopes eventually to make a connection. The point where the cave turns is almost under the porch of the De Menil house, where we used to relax at lunch or in the evening, 40 or 50 feet straight above our diggings.
A more talented and imaginative writer might contrast these superposed scenes in a sort of allegory. In the upper world it is spring. The air is warm and balmy, and the sun is shining. The grass is green and sprinkled with violets. Bushes and trees are in bloom, and innumerable birds are setting about their seasonal loves and labors. The caretaker’s pretty baby girl toddles about, learning to walk. The world of life is developing its future in a scene just old enough to be leisurely and pleasantly mellowed.
In the lower world there are no seasons. The motionless air is always cool but never cold. The humidity is always near 100% and nothing is ever quite dry. The white limestone ceiling is dewey as if perspiring quietly, and water drips slowly from the tips of the scattered stalactites. The water is limpid but it carries in solution minute quantities of lime, the slow, imperceptible precipitation of which through the ages has formed the stalactites, stalagmites, and cave onyx, all forms of what has appropriately been called dripstone. Yellow lights illumine a scene that has never known the sun and make temporary islands of light in a sea of absolute darkness that has been lightless for hundreds of thousands of years. Smeared from head to foot with yellow mud, workmen slide along the narrow passage, digging out the sticky clay, penetrating still farther into the mysterious entrails of the earth where man has never been before. In spite of this rash intrusion, the strange scene seems as ancient and timeless as a tomb. And it is a tomb, a place of mass burial, sealed away as a monument of the dead past, before the first Indian ever hunted a deer along the top of the hill inside which it lies.
That filling of clay is an exasperating and expensive nuisance to the men who want to reopen the old cave channel, but it is a delight to the bone-digger. It was in this clay that the workmen found the bones that brought us to St. Louis, and we began finding more bones as soon as we dug into it for ourselves. In the week that we were there, we found too many bones to count, but we guess that we excavated between 2,000 and 3,000 of them, some almost too small to see while others were large, complete skulls.
As we dug bones, we began our detective work. What the bones are is perhaps the least part of the mystery, and their identification had to be done back in New York, anyway, where we could study and compare the bones at our leisure. Here the problem was how the bones came to be here, in the core of Arsenal Hill under the De Menil house. Some clues are still missing and a more fortunate detective than I may prove someday that I am wrong, but we did soon find enough clues for a tentative solution of the mystery.
As Clue No. 1, there is the cave itself. By that I mean the long, branched, channel-like cavity in the limestone, regardless of the fact that it is or has been nearly filled up with clay. It averages 20 to 25 feet wide, with solid limestone walls and ceiling. We do not know how long it is, where it comes from, or where it goes to: important missing clues. We do not even know how deep it is or what the floor is like, because as deep as anyone has yet dug (12 to 15 feet in places), the bottom of the clay has not been reached.