On the occasion of the launching of the first balloon in Italy, a very interesting discussion was raised with regard to raising surfaces in the atmosphere and propelling them downwards — as to whether we experienced the same resistance. Professor Hergesell, of Strasburg, very kindly arranged for some experiments to be carried out. The apparatus was rigged up, and we tried spheres and discs of varying diameters; but with the spheres we were very much bothered, and I may say our chief trouble was with the vertical currents in the tower of the Cathedral. However, the experiments are still going on, and so far we have found that the spheres rise vertically quicker than they descend. It is rather difficult to understand this.