Some of the things described in this book are little known to the average reader, while others are well known; but all possess the fascination of whatever is strange, marvellous, obscure, or mysterious magnified, in this case, by the portentous scale of the phenomena. The idea of the author is to tell about these things in plain language, but with as much scientific accuracy as plain language will permit, showing the wonder that is in them without getting away from the facts.