With the completion of the shaft, scientific exploration began. Various scientists around the state summited projects they thought would be worth while. Dr. Christianson of Grinnell made an extensive study on insects and mold spores that might be found in the cave. The atmosphere and purity of the water was investigated. The temperatures were taken by barometric pressure. Even the slopes of rising and falling water were recorded. Some scientist took either two or three rock samples of all the formations found in the cave and analyzed them for age determination. As I recall the oldest one dated back about 80,000 years. However, there is no doubt that the age of the cave itself is considerably older then the formations. It is believed by many scientist, and myself, that the cave could go back several million years. Strong evidence suggests that the extensive mud banks lining the passageway maybe left over from the last glacial episode, here in Iowa. When the glaciers melted a considerable amount of water entered the cave and carried mud in with it, depositing the mud along the banks. As the water recede the mud was left there. Some of these ancient mud banks have been complete covered over with flow streams that are up to an inch thick. Therefore, the mud has been there at least the length of time it would take for each flow stream to be deposited, at least several thousand years.