[ 32 ) ihe Origin of the sudden blow can only be more or.less plausibly conjectured. Various conceivable causes may, ai different times and under different conditions, communicale a shock to the subterranean regions. Such are the falling in of the roof of a sublerranean cavily, the explosion of a volcanic orifice, or the sudden snap of deep-sealed rocks subjected lo prolonged and intense sirain. Each of these dislrubances no doubt from lime io time gives rise to earthquakes. (Geology by Sir Archibald Geikie, Vol. 1. Page 338). li seems sirange that a geologisi of the eminence of Sir Archibald should think of ihe fool-slops of birds and beasis as likely lo cause iremors on such a huge body as the earlh. The earth, as is well-known, is a great storehouse of electric energy. Indeed it is one of the besi conductors of electric current and serves as a huge and safe negative pole io most of our electric enterprises. This close connection of the earlh with electric energy will be evident io us, laymen, from the following facis. If a person louches a live clectric wire of ö sufficiently high voltage, he at once dies, while i} he does this, standing upon a rubber sheel, a piece of dry wood or upon any substance which is a non-conductor of electricity, nothing happens. Again, it has been seen that,
