Transactions of the Royal Geological Society of Cornwall (Volume 11) (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: one particular day twenty-four were counted. Superintendent Charles Foreman told the author, when he visited Virginia city in 1882, that special observations were made to determine whether these shocks were felt as severely deep down as on the surface where they were on the verge of being destructive. The universal testimony of many observers was, that in most cases they were not felt at all underground, and when a shock was felt it was extremely feeble. At the Takashima Colliery, near Nagasaki, which is worked extensively under the sea, the earthquake shocks are seldom felt underground, but a good deal of gas is encountered in the workings, and as it appeared to escape several hours before any marked changes in the barometrical column, and as minute vibrations or earth tremors were deemed to accompany barometric depressions, it was thought important to establish a subterranean observatory, and to study the connection between such microscopic movements of the rock and the escape of gas. But the heavy settlements consequent on the working of three seams, with an aggregate thickness of 30 to 30 feet, entirely vitiated the record of minute tremors, and the observations by microphone and micro-seismometer are stated to have been "totally unreliable." Two chapters of this interesting work?the one on the Cause of Earthquakes, the second on Predictions and the giving of warnings of coming Earthquakes?are suggestive and in part very amusing, but I feel that the time and the results of observation are not yet sufficiently advanced to entitle me to lay before a general audience so much that is speculative, with not a little which has rather too fantastic an air. I must, however, say a word on one phase of the earthquakes which are accompanied by eruptions, and in a groat measure on...