Ballons and Diving-Bells
In the first place, an argument which necessarily rests on probability only, I think worth very little; but, granting this position, I conceive that the state of science, of knowledge, &c., of that age, will bear so little comparison with that of the present day, that the parallel must fall to the ground. Though he did not convince me, he surprised me, by telling me how much had been done latterly. By observations on the different currents of wind, with the power of ascending by increasing the quantity of gas, of descending by throwing out ballast, they have acquired some little power of directing the balloon.
But the most important discovery is one made by Sadler, which enables them to measure with tolerable accuracy the rate of their flight. A long log-line is thrown out, and by measuring with great accuracy, by means of a quadrant, the angle which this line makes, they can ascertain the velocity of their flight, and from observation of the compass may form a tolerable idea of their situation.
Nugent tells me that a young friend of his ascended with Graham a little time ago ; it was one of the lovely bright calm days which have been so frequent this summer ; still, in the elevated regions of the atmosphere, the cold was intense; but no peculiar sensation accompanied this cold. George (Lord N.) said he asked what was the appearance of the horizon of the earth: ' Cloud,' was the answer ; ' the view was always caught through clouds, which formed an irregular fringe or frame to the picture.'
The descent was very perilous: the young man—almost a boy—having asked Graham how high they were, and being told, I forget what, asked ' whether they could not ascend a little higher before they began their descent ?' Graham said. Certainly they could, but that he was averse to the idea of expending any more gas, because a small quantity in reserve might be essential to the safety of their descent. "When once the ballast is all thrown out and the descent begun, the only means of avoiding any dangerous spot on which the balloon might chance to fall, is by admitting a little more of the inflammable gas, rising, and trusting to the wind to convey the machine out of the dangerous neighbourhood. The young man still pressed for a farther ascent; Graham weakly consented; and the danger he had foreseen actually occurred.
As soon as the earth became visible through their glasses, it was evident that they had their choice of dangers only: they were coming down between the river and some lime-kilns. The kilns were certain destruction ; the moment the balloon approached them. The inflammable gas must have ignited, and they must have been burnt to death. The only alternative was to rise and trust to the wind for conveying them out of this dangerous neighbourhood. They had no gas left, and the only means of lightening the balloon was by cutting away the car—without the power (as George observed) of saying ' heads below'—-and trusting themselves to the ropes of the balloon itself, which of course rose, having a lighter weight, made still lighter by being close to it, instead of being attached at some distance. At last they fell into the river, and being both good swimmers, escaped.
I forgot to say that another of the modern contrivances is a pulley, by means of which the aeronaut can draw the car farther from or nearer to the balloon: by this means the ascent or descent may be checked, and more or less advantage may be taken of the current of wind in which they may happen to find themselves.
London, he says, appeared wonderfully regular at this great elevation: every smaller distinction of height disappeared ; every building appeared of equal height and of dazzling whiteness.
This conversation naturally led us to the diving-bell. I found George had been down in one, in Plymouth Sound. By his account, it must have been precisely similar to that which I saw at Bordeaux. He says, when under the water, you see in the diving-bell about as clearly as you would in a carriage, when the breath has been congealed on the glasses; though you see very little without, within you can see to read the smallest print.
He says, the first thing his companion did, was to direct his attention to the code of signals attached to the side of the bell, and explain them, that George might know what to do in the improbable event of his companion's being seized with a fit. The signals are given by so many strokes of the hammer against the side of the bell: the first, and most important of all, which is ' Hold fast where you are,' is given by one stroke; the second, which is, I should have thought, still more so, is ' Draw up the bell;' the others direct it to be drawn N., 8., E., or W.
His companion said, ' Now, you see that pointed rock: if we go on in our present course, the side of the bell must strike against it; it will be overset, and we shall inevitably be destroyed: but there is no hurry; we will go nearer and examine it.' When they approached he gave the signal to be drawn up higher; then directing the course so as to come immediately over the rock, he desired to be lowered again, and they found themselves with the point of the rock within the bell.
George describes the painful sensation in the ears exactly as the man at Bordeaux did; a buzzing and sense of pressure like that arising from a drop of water in the drum of the ear, only stronger. Cotton to deaden this sensation would be a very dangerous experiment: the compressed air would drive it in so far, it would not be got out again without some instrument.
He says, that altogether the sensation is so little disagreeable, that he conceives one might remain under water for any length of time. In returning to the air, there is a disagreeable sulphureous smell, for which it is not easy to account, but which is always observed. George did not know whether this smell was experienced returning from fresh water as well as from sea water.