emanation employed can fit in the finest capillary glass tubing and the hairlike tubes can in turn be placed in fine exploring needles. There is comparatively little inconvenience to the patient in inserting these needles, and there is the most perfect control of the dosage in the number and strength of these tubes and the duration of exposure.[1] The first Radium Institute in Ireland has already done good work for the relief of human suffering. It will have, I hope, a great future before it, for I venture, with diffidence, to hold the opinion, that with increased study the applications and claims of radioactive treatment will increase. [1] For particulars of the new technique and of some of the work already accomplished, see papers, by Dr. Walter C. Stevenson, _British Medical Journal_, July 4th, 1914, and March 20th, 1915. 259 SKATING [1] IT is now many years ago since, as a student, I was present at a college lecture delivered by a certain learned professor on the subject of friction. At this lecture a discussion arose out of a question addressed to our teacher: "How is it we can skate on ice and on no other substance?" The answer came back without hesitation: "Because the ice is so smooth." It was at once objected: "But you can skate on ice which is not smooth." This put the professor in a difficulty. Obviously it is not on account of the smoothness of the ice. A piece of polished plate glass is far smoother than a surface of ice after the latter is cut up by a day's skating. Nevertheless, on the scratched and torn ice-surface skating is still quite possible; on the smooth plate glass we know we could not skate. Some little time after this discussion, the connection between skating and a somewhat abstruse fact in physical science occurred to me. As the fact itself is one which has played a part in the geological history of the earth, [1] A lecture delivered before the Royal Dublin Society in 1905. 260 and a part of no little importance, the subject of skating, whereby it is perhaps best brought home to every one, is deserving of our careful attention. Let not, then, the title of this lecture mislead the reader as to the importance of its subject matter.