Finding that the cords with which his dirigible balloon cars were suspended offered almost as much resistance to the air as did the balloon itself, Santos-Dumont substituted piano wire and found that the alteration constituted greater progress than many a more showy device. He altered the shape and size of his No. 4 to a certain extent and fitted a motor of 12 horse-power. Gravity was controlled by shifting weights worked by a cord; rudder and propeller were both placed at the stern. In Santos-Dumont's book there is a certain amount of confusion between the No. 4 and No. 5 airships, until he explains that 'No. 5' is the reconstructed 'No. 4.' It was with No. 5 that he won the Encouragement Prize presented by the Scientific Commission of the Paris Aero Club. This he devoted to the first aeronaut who between May and October of 1900 should start from St Cloud, round the Eiffel Tower, and return. If not won in that year, the prize was to remain open the following year from May 1st to October 1st, and so on annually until won. This was a simplification of the conditions of the Deutsch Prize itself, the winning of which involved a journey of 11 kilometres in 30 minutes.