which it was thus made to revolve, without the necessity of confining
it to the one level.

The rate of motion which the Balloon thus equipped is capable of
accomplishing varies according to the circumstances of its propulsion.
When the Archimedean Screw precedes, the velocity is less than when
it is made to follow, owing to the reaction of the air in the former
instance against the car, the under surface of the balloon, and other
obstacles, by which its progress is retarded. Again, when the cord
upon which it travels is most tense and free from vibration, the rate
is found to be considerably accelerated, compared with what it is when
the contrary conditions prevail. But chiefly is its speed affected
by the proper _ballasting_ of the machine itself, upon which,
depends the friction it encounters from the cord on which it travels.
Under ordinary circumstances it proceeds at a rate of about four miles
an hour, but when the conditions alluded to have been most favourable,
it has accomplished a velocity of not less than five; and there is no
doubt that were it altogether free from restraint, as it would be in
the open air, with a hand to guide it, its progress would be upwards
of six miles an hour.

Having now, I trust, sufficiently explained the principles exemplified
in the model here described, it may be expected that I should add a
few words regarding their reduction into practice upon a larger scale
and in the open air, with such difficulties to contend with as may be
expected to be encountered in the prosecution of such a design. In the
first place, however, it will be necessary to disabuse the public mind
of some very prevailing misconceptions with respect to the conditions
of a Balloon exposed to the action of the winds, pursuing its
course under the exercise of an inherent propulsive power. These