The application by Dr. Johnston-Lavis of the theory of the secular straining of the Earth, with which my name and Mr. Davison's is connected, to an explanation of the deeper phenomena of volcanic action, is ingenious and suggestive. It will, therefore, I trust, be of some use if I am allowed to discuss and criticize the principles and propositions that appear to me to be necessarily involved in the views put forth by Dr. Johnston-Lavis. Before doing this, I feel it incumbent upon me to point out that Mr. O. Fisher's position with regard to the question seems to have been misunderstood. So far from occupying an antagonistic position, he has done much to mathematically develop the theory; and it is only when we come to its practical application to the explanation of geological phenomena, that he, myself and Mr. Davison differ.