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   The change of dimension of the bulk of the inclosed gas by change of temperature between day and night, is to be compensated by a balance rope. When the sun increases the levitating power of the air float, it will soon find its equipoise in lifting from the surface of the sea, or the land its equivalent of the balance rope, and its loss by the coolness of the night by giving back to the land or water its equivalent of weight.
   I have practiced this current sailing for over thirty years, more or less, made over 400 voyages-from 100 to 1,000 miles in length-and never failed to find these trade-wind currents when an altitude of 5,000 to 12,000 feet was attained although at these times currents from opposite directions frequently prevailed on the surface of the earth. An air vessel of 100 feet diameter, two thirds filled with coal gas, would have a net carrying power of 9,000 pounds, and would be all sufficient for a practicing machine with a view to sound these currents across the ocean and to test the practicability of establishing an air line of mail and passenger conveyance from this country to Europe.  Pleasure seekers and invalids would find it a swift and easy voyage from America to Europe-no sea-sickness and less than three days to make the voyage. 
   This is certainly a feasible plan for the inauguration of trial trips, and is seriously worthy the attention and application of the enterprise and genius of the present day and in our own nation.  A little barometrical practice in scheme would soon teach us how to lay our lines for successful system of trans-Atlantic aerial navigation.

[New article clipping]
A Proposition to Navigate the Air.
   ROBERT BONNER, Esq.: Dear Sir-Although not personally acquainted with you, your general reputation opens me the door for an introduction, and without further preliminary to invite your attention to the following proposition: namely, to carry for you a New York Ledger mail package to England or France within the space of three days-say from the city of New York to any of the principal cities in England.
   I have been endeavoring, for the last twenty years, to get aid in giving practical utility to aerial navigation, but have thus far failed in enlisting sufficient capital for an experimental demonstration of the fact.  Not long ago I read a paper on the subject before the Franklin Institute, briefly explanatory of its practicability, a copy of which you will find in the New York Scientific American of January 8, 1870; and in November last, at the request of a friend desirous of learning the opinion of the Smithsonian Institution upon my "upper current" theory-I may say practice-I received from the following reply:
"SMITHSONIAN INSTITUTION, WASHINGTON, D.C., Nov. 20th, 1869.}
"DEAR SIR-In the absence of Prof. HENRY, who is at Macon, GA., I send you two copies of his Report for 1865, in which you will find his views relative to the constantly prevailing current of wind from the west, in the upper regions of the atmosphere.  The existence of these currents is an established fact of science, confirmed by every day's experience.  We take great interest in the success of your transatlantic voyage, and have no doubt that you are the very best person to undertake the enterprise.  Yours respectfully,
"WM. J. RHEES, Chief Clerk.
"JOHN WISE, Esp., 1217 N. 15th St., Philadelphia."

But with all this, I have not been enabled to secure the aid of eight or nine thousand dollars with which to build the Aerocraft, to put the experimental project through, and for the simple reason, that no one can see the money coming back, or, in other words, that it will not pay.  Cannot you make it pay?  I have one thousand dollars to put in it, and if you will furnish the balance, I will let yours come out first, and take mine out of the remainder, and then divide the balance.  I think the first mail carried over would pay--could be made to pay the cost of outfit.
Should you take sufficient interest in this proposition to allow me a personal interview, I feel assured that I could convince you of the feasibility and certainty of the enterprise, and within the limits of cost above mentioned.  Very respectfully yours,
JOHN WISE.
(We never invest in such enterprises; but we give Mr. Wise the benefit of the publication of his letter.--Ed. Ledger.)

Water as a Fulminate.
Messrs. Editors:--The active investigations going on at present concerning steam-boiler explosions seem to demand all the scientific knowledge and facts as far as known of the characteristics of water. I have examined it, and witnessed it, as a fulminate in two different conditions. In the one case, in the spherical state on a hot, metallic plate; in the other in a similar condition from a mixture of warm and cold air in a storm-cloud. In both cases it plays the part of a fulminate. When I drop water on a hot plate, below a red heat, it rolls about without making noise or steam. When the spheroid is rolled over the edge of the hot plate on to one of lower temperature it explodes. If, however, it be struck with a hammer while rolling about on the hot plate it goes off like a fulminate, resembling the crepitating noise of thunder, as heard by an observer immediately above the cloud in which it occurs.

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In the case of spheroidal water, as noted in "Silliman's Principles of Chemistry," the author says "Water passes into this condition at 340 [[degrees?]], and may attain it even at 288 [[degrees?]. A grain and a half of water in this state at 392 [[degrees?]] requires 3.30 minutes to evaporate." If you drop the water on a plate of low red-heat it oxidizes the plate, and necessarily deoxidizes the water, freeing its hydrogen. Now it is well known that water in a spheroidal condition is ensconced in an atmosphere of its own vapor, and this vapor being a non-conductor, chemists say its formation abstracts the sensible heat from water, and leaves the temperature of the fluid at 205 [[degrees?]]; and this would seem to be a correct statement, as I find my spheroid to leave no watery track as it floats on its vapory cushion over the hot plate undisturbed, but as soon as it is struck with a hammer the watery trace becomes visible on the plate and on the hammer. This envelope of the spheroid must be of considerable tenacity, as indicated by its bursting and fulmination when struck with the hammer. 

The book referred to says, "If a thick and heavy silver capsule is heated to full whiteness over the eolipile, it may by an adroit movement be filled entirely with water, and set upon a stand, some seconds before the heat declines to the point when contact can occur between the liquid and the metal. When this happens, the water, before quiet, bursts into steam with almost explosive violence, and is projected in all directions."

Now let us apply these known characteristics of water to its action in steam boilers, and see whether it can account for some of those terrific explosions too frequent of late. 

As soon then as a heat of 340 [[degrees?]] accumulates in the boiler plate it produces the spheroidal state in the water in contact with it, and as long as that temperature is maintained, the spheroidal condition continues, and if all that boiler surface covered with water attains that temperature, its inclosed water immediately becomes a spheroid inclosed in its fulminate shell, ready to burst explosively as the drop in the eolipile, as soon as the temperature falls to the maximum steam-generating heat. In a tubular boiler of comparative great water surface to a given capacity of water room, such high temperature of boiler shell is soon acquired upon a cessation of motion in the engine; and vice versa, when the furnace doors are suddenly thrown open allowing a rush of cold air to the boiler shell, causing this tenaciously bonded fulminate to give out suddenly its pent up power, as do the insidious granules of gunpowder in the bomb-shell, when they are touched by that mysterious agent, fire. 
The work referred to says "The quiescence of the spheroid of water, as it rolls to and fro over the heated plate, is due to the elastic force of its own vaporous atmosphere, as well as to the repulsive action of hot surfaces." This is not a lucid explanation to my comprehension. I suggested to a high authority of science that electricity played a conspicuous part in the phenomenon, but was told it did not. I hold that head, oxygen, fire, and galvanism, are only different forms or modes of that one mysterious element we dominate electricity, and that in the spheroid of heated water is positively-electrified repulsive power is balanced by the equally positively-electrified heated boiler shell; and that a change, or reduction of the electrical tension int he heated plate, rending it negative to the electrical tension in the spheroidal atmosphere of the water, will necessarily cause an explosion. 
But lay the electrical theory aside, and take the simple fact of water 'in a spheroidal state,' as explained by M. Boutigny--the water int eh capsule--the experiment of Perkins, and the water on the hot plate, and we have the evidence that water in a boiler may, and does, become spheroidal at a temperature of 340 [[degrees]], and must then float about upon its self-created atmosphere, exerting just as much repulsive pressure against the shell of the boiler, as does the heated boiler shell against the water, bringing the two forces into equilibrium; and that as soon as this balance of power is broken, by and of the causes always incident to such conditions, an explosion must follow. The atmosphere surrounding the spheroid suddenly expanding into a large volume of steam, while at the same instant its liberated heat converts the inclosed liquid into an additional volume of steam, and, unless such boiler is made with the same comparative power of resistance as a gun-barrel is made, it will burst; that is to say, if it has not a vent or opening like the gun-barrel, to let off the expanding force, and a sufficient resisting strength for the initial shock, an explosion must result.
Boiler explosions have always on examination appeared to me more like the explosion of a bomb-shell than one caused by the gradual augmentation of steam pressure over and above the resisting strength of the boiler. That steam boilers may explode from this simple cause of over-pressure, is not to be denied, but in all such case they must at best be but poor magazines of power.
My article being already long, I will omit from present the analogous fulminating characteristics of water spheroids as formed by the commixture of cold and warm air in the formation of a thunder cloud, and the electrical explosions they give rise to as they fall from the upper to lower cloud.
Lancaster, Pa.   John Wise