Many attempts have been made to improve the top valve of the balloon. In connection with these attempts it will be sufficient to mention the names of Messrs. Giffard and Lefébre. I have myself proposed a valve pipe in the interior of the balloon, and which, by its more or less elevation, should permit a regulated escape of gas. (Aëronaute, May 1st, 1872.) As neither of these plans have been practically applied I am unable to say how far they would realize their theoretical promise. But it has since occurred to me that there remains a means yet more simple for attaining the same result, which is to do away with the valve, entirely, and to raise the apparatus in the interior of the balloon by means of a cord and pulley.