MR. JAMES B. LEWIS said, as one who had over 10 years' experience of the field, and who had been compelled to study it closely from a practical point of view, he had naturally formed some theories as to the origin of the tin formations. Having studied the literature on the subject-various Government and other reports-he found that the theories there propounded did not quite agree with the facts as he learned them. He found that the pegmatite seams usually accompanied the tin formations, overlying them at a flat angle; that the tin did not penetrate the altered granite to a great depth from these seams; that the granite over these seams was of a different character. The conclusion he came to was that fractures had occurred in the rock when cooling; that the solutions carrying the tin had come up through these passages, and had penetrated the still plastic rock on the one side, and that the fractures had subsequently been filled with pegmatite. That theory Mr. M. S. Moore had practically adopted. The facts so far stated agreed, however, just as well with the view taken by K. B. Lewis, viz.:- "The author of the article under consideration has gone to some trouble to try and explain the genesis of a somewhat unusual occurrence of tin ore. His theory, if correct, is very interesting, and deserves further investigation. Being well acquainted with his type area, I would like to point out that the deposit may be due to the good old-fashioned pneumatolysis of the margin of a granitic intrusion.