Nothing daunted, the inventor began the construction of _Santos-Dumont No. 6_ immediately, finishing it just twenty-eight days after the construction of _No. 5_. A peculiarity of this balloon was that it was barely self-sustaining except when forced through the air by the propeller. The long cigar-shaped gas-bag was relatively small, and was filled to its limit of capacity with gas, while the lifting power was counterbalanced by the operator, car, engine, and ballast, so that the entire structure weighed practically the same as the air it displaced. At the stern was a powerful propeller. Obviously, then, if the long spindle-shaped machine was tilted upward at the forward end, and the propeller started, it would be driven upward; while if the forward end was lowered the propeller would drive it downward. If it was balanced so as to be perfectly horizontal, it would be forced forward in a horizontal direction. Deflections to right and to left were obtained by the ordinary type of vertical rudder; and thus any direction could be taken. [Illustration: AN ENGLISH DIRIGIBLE BALLOON. The photograph here reproduced gives a very vivid impression of the cumbersome nature of balloons of this modern type, and suggests the difficulties to be met in housing them safely when not in use.] To obtain the desired angle of inclination, Santos-Dumont made use of a sliding weight, and with this he guided his balloon upward and downward by shifting its position. Thus, although this balloon was a veritable balloon rather than a "flying-machine" proper, it really lacked the one essential common to balloons: it would not rise until propelled by mechanical means. It lacked the requisite of the flying-machine, however, in that it was not "many times heavier than the air." After giving this new balloon several preliminary trials, which included such exciting incidents as collisions with a tree in the Bois du Boulogne, an official attempt was made on October 29th, 1800. Above the heads of the gaping thousands, who, to a man, wished the daring navigator success, the balloon rounded the tower, and in twenty-nine minutes and thirty seconds from the moment of starting--thirty seconds less than the prescribed time-limit--the trip was successfully terminated.