ion of sparkling coruscations." Green, in his
stormy ascent from Newbury, England, witnessed a thunderstorm below
him, as will be remembered, while an upper cloud stratum lay at his
own level. It was then that Green observed that "at every discharge of
thunder all the detached pillars of clouds within the distance of a mile
around became attracted."

The author will have occasion, in due place, to give personal
experiences of an encounter with a thunderstorm which will compare with
the foregoing description.

CHAPTER IX. EARLY METHODS AND IDEAS.

Before proceeding to introduce the chief actors and their achievements
in the period next before us, it will be instructive to glance at some
of the principal ideas and methods in favour with aeronauts up to the
date now reached. It will be seen that Wise in America, contrary to the
practice of Green in our own country, had a strong attachment to the
antique mode of inflation with hydrogen prepared by the vitriolic
process; and his balloons were specially made and varnished for the use
of this gas. The advantage which he thus bought at the expense of much
trouble and the providing of cumbersome equipment was obvious enough,
and may be well expressed by a formula which holds good to-day, namely,
that whereas 1,000 cubic feet of hydrogen is capable of lifting 7 lbs.,
the same quantity of coal gas of ordinary quality will raise but 35 lbs.
The lighter gas came into all Wise's calculations for bolder schemes.
Thus, when he discusses the possibility of using a metal balloon, his
figures work out as follows: If a balloon of 200 feet diameter were
constructed out of copper, weighing one pound to the square foot;
if, moreover, some six tons were allowed for the weight of car and
fastenings, an available lifting power would remain capable of raising
45 tons to an altitude of two miles. This calculation may appear
somewhat startling, yet it is not only substantially correct, but Wise
entertained no doubt as to the practicability of such a machine. For its
inflation he suggests inserting a muslin balloon filled with air within
the copper globe, and then passing hydrogen gas between the muslin and
copper surfaces, which would exclude the inner balloon as the copper one
filled up.

His method of preparing hydrogen was practically that still adopted
in the field, and seems in his hands to have been seldom attended with
difficulty. With eight common 130-gallon rum puncheons he could