Prof. JANSSEN, Delegate of France. My honorable colleague, General STRACHEY, thinks that longitude is longitude, and that there is not an astronomical longitude and a geographical longitude. I answer, that this is, nevertheless, what the nature of things indicates. The longitude of observatories, or rather the difference of longitude between those establishments, must be fixed with an accuracy which is never sufficiently great. In the Bureau of Longitude of France we are occupied with the differences of longitude of European observatories, and we adopt for these calculations all the latest scientific improvements, and especially the employment of electricity. Geography, especially for general purposes, does not require this great accuracy, which could not be expressed on maps. All geographers agree upon that subject. A statement of the longitude is like the statement of a weight, of a measure, or of anything, and its precision must vary according to the purpose to which it is applied. Is not a weighing necessary to determine a chemical equivalent of an entirely different kind from that of a commercial weighing? Yet it is still a weight. Is it necessary to insist on this further? It is entirely a secondary question. If General STRACHEY, whom I had the pleasure of meeting in India, demands that the prime meridian should be connected with observatories with rigorous accuracy, this can be done if it be desired; the astronomical and electrical methods at our disposal will permit of it. Prof. ABBE, Delegate of the United States, said that he was quite interested in the determination, if possible, of what is a neutral meridian. We are precisely in the condition in which we were years ago, when the French Institute determined that the basis of the metric system should be the one ten-millionth of the quadrant of the globe. Having settled upon that ideal basis, they spent years of labor, and finally legalized a standard metre, which is still preserved at Paris. We have now the same problem to solve. We have before us the idea of a neutral meridian, and, if it be adopted, we must see that there be embodied in the system the distance of certain other important places with reference to it. The only suggestion given as to the location of this neutral meridian is Behring's Strait. This is said to be a neutral meridian, because it lies between Russia and America; but how long will it remain so? Perhaps a year or two, or perhaps fifty years. Who knows when Russia will step over and reconquer the country on this side of Behring's Strait? Who knows when America will step over and purchase half of Siberia? At any rate, that point is not cosmopolitan; something must be found which is fixed, either within the sphere of the earth or in the stars above the earth--something that is above all human considerations--otherwise we shall fail in securing a neutral meridian.