At a recent meeting of the Boston Natural History Society, Professor Wm. B. Rogers stated that, a number of years since, he had made some experiments in the stalactite caverns of Virginia, for the purpose of obtaining data in regard to the age of these deposits. He placed vessels in an unfrequented part of the cave, beneath drippings of various dimensions, where they remained for a period of from five to seven years. He arrives at the conclusion, as the result of his observations, that the rate of accretion is one-tenth of an inch in five years, or an inch in fifty years. As there are several feet of accumulated deposit in some places, he thinks that the process must have been going on for at least five thousand years.