The PRESIDENT. The Chair sees upon the floor to-day, as the guest of this Conference, one of the most distinguished scientists, who was invited to be present at our meetings, Sir WILLIAM THOMSON, whose name is known the world over in connection with subjects kindred to this we are now discussing. If it be the pleasure of the Conference to ask Sir WILLIAM THOMSON briefly to express his views, the Chair would be very happy to make the invitation. The Chair, hearing no dissent, takes pleasure in introducing Sir WILLIAM THOMSON. Sir WILLIAM THOMSON. Mr. President and Gentlemen, I thank you for permitting me to be present on this occasion, and I thank you also for giving me the opportunity of expressing myself in reference to the subject under discussion. I only wish that the permission which you have so kindly given me may conduce to the objects of this Conference more than I can hope any words of mine can do. The question immediately under discussion is, I understand, the proposal that the meridian passing through the centre of the instrument at the Observatory of Greenwich shall be adopted as the initial meridian of longitude, and it does seem to me that this is a practical question; that this resolution expresses a practical conclusion that it is expected by the world the present Conference may reach. It is expected that the resolutions adopted will be for the general convenience, and not for the decision of a scientific question. It is the settlement of a question which is a matter of business arrangement. The question is, what will be most convenient, on the whole, for the whole world. It cannot be said that one meridian is more scientific than another, but it can be said that one meridian is more convenient for practical purposes than another, and I think that this may be said pre-eminently of the meridian of Greenwich. I do most sincerely and fervently hope that the Delegates from France and from the other nations who voted for the preceding resolution will see their way to adopt the resolution that is now before the Conference. It does seem to me that it is a question of sacrifice, and I do trust that the honorable Delegate from France who spoke last, Mr. LEFAIVRE, will see that France is not being asked to make any sacrifice that it was not prepared to make. In the admirable and interesting addresses which Mr. JANSSEN has given to this Conference, (which I had not the pleasure or satisfaction of hearing, but which I have read with great interest,) the readiness of France to make a much greater sacrifice than that which is now proposed was announced. The amount of sacrifice involved in making any change from an existing usage must always be more or less great, because it cannot be said that it is a matter of no trouble to make such a change; but what I may be allowed to suggest is that the sacrifice which France was ready to make would be very much greater than that which would be made by adopting the resolution now pending.