THANKS to the indefatigable zeal of General de Nansouty and the engineer Vaussenat, a meteorological observatory has already been erected on the Pic du Midi. After visiting the place with the Director of the Higher Instruction on the occasion when this observatory was handed over to the State, Admiral Mouchez came to the conclusion that it might be possible to establish an unrivalled astronomical station on the summit, which is now perfectly habitable. In the month of August last he did us the honour of requesting us to study on the spot the advantages and possible drawbacks attending an installation made under such exceptional conditions. The details of our observations will form the subject of a special memoir far too extended for insertion in the Comptes Rendus. For the present our remarks must be limited to a simple communication of the more interesting results obtained by us from August 17 to September 22.