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[[tury]], also tables for size, capacity, &c., with instructions how to cut and build a Balloon. This book has been the means of dozens of ignorant mountebanks dubbing themselves Professors, and making local ascensions of a few thousand feet.

The great Air Ship "City of New York" has a capacity of 725,000 cubic feet of gas. Her weight and what she would have to support with the Car, Boat, and ten passengers, with baggage and provisions, would be less than three tons. Supposing she had only 500,000 cubic feet (the least she can carry,) of Carborated Hydrogen, (the heaviest, or having the lease ascensive power of any gas,) which has an elevating power of forty pounds to the thousand cubic feet, she would have a surplus acensive power of seven tons, which must be supplied with ballast-Where is it to be put? This question was put to (Prof.) Lowe one day before his contemplated departure last Fall, and no answer given--this probably had something to do not only with the sudden illness of Capt. Carr, who was to navigate the boat, but with the abandonment of the enterprise by Messrs. Gilbert, Ballon, Wood & Co.

Prof. Wise, with La Mountain, Gager, and a St. Louis Editor, travelled 1,100 miles in the "Atlantic," with only 58,000 cubic feet of gas, in 19 hours, and had there been but two in the car the voyage would have been made (or attempted at least) to Europe. Prof. Wise is not at work upon this his favorite subject, and investigating the merits of a new invention by Mr. Gage of 215 Fulton-st., which if found, as he hopes, will enable the Prof. to guide a baloon through the air against or with a current. And if Prof. Wise, with all his experience and education, cannot succeed, we surely need not look to the hero of ten local ascensions of a few hundred feet to succeed.

Atmospheric Electricity

The following condensed account of a lecture delivered by Professor Henry, of the Smithsonian Institution, on the 2d instant, during the sitting of the of the American Scientific Association at Newport, Rhode Island, furnishes the chief points of a discourse which, it is plain to see, was of great value and interest, as it was highly appreciated by the intelligent assembly that heard it. The conclusions as to the causes and accompanying phenomena of thunderstorms gratify by their simplicity and distinctness:

Professor Henry gave an exceedingly interesting lecture at Aquiduock Hall on atmospheric electricity. He first stated the many theories which from time to time had been given relating to the origin or source of the subtle fluid or element. It had been supposed to be produced by the friction of the currents of air in motion. It had also been attributed to growing vegetation; also, to evaporation. It was well known that boiling salt water produced electricity. Steam blown off from a locomotive was a source of electricity, but it was frictional. Upon the whole, the origin of atmospheric electricity was not conclusively ascertained. There is a theory that the atmosphere is not electrical per se, but only by induction; that the earth is electric, and the air was only electric under certain conditions. This was [[Paicher's?]] theory. It had been adopted by some European physicists, and he must say it had not received the attention it deserved. The late Dr. Hare, of Philadelphia, entertained a similar theory--that the earth was plus electrical and the air minus.

It was certain that the amount of electricity in the air varied with the amount of vapor presented. On clear, dry, cloudless days, there was but little electricity to be detected by the electronometers and it was only when we had masses of vapor in the form of clouds that there were electrical discharges. If a polished iron rod, two or three feet in length, with a polished brass or iron ball at both ends, be held horizontally, there will be no sign of electricity in the red, but if it be held vertically it instantly becomes electrical. The end nearest the earth will be plus electrical, and the upper end minus. If the rod be held near the ground, and then raised as high as a man can reach, the electronomoter indicates a change of electrical condition; when near the ground it is most electrical. The electronmeter at the Smithsonian Institute showed great changes in a few feet elevation. It had been demonstrated that the electricity was repelled by the atoms of matter composing the earth into the air. He used the word repelled as best expressing the idea. It had also been demonstrated that an [[en?]] atom of electricity at the surface of the globe acted in concert with the globe itself in repelling a second atom of electricity outside the first. The repelling power was inversely as the square of the distance. Prof. Henry then gave the phenomena of explosive atmospheric electricity.

No thunder storm can occur until there are two layers of clouds. The electricity is carried in to the air by the masses of vapor going up from the earth. Vapor rising from the earth always carries more or less electricity with it. He had ascertained these and other interesting facts from Mr. Wise, the balloonist, with whom he had been in correspondence, and who had undertaken experiments. Mr. Wise said that in passing through a thunder storm he was always first carried through a dense cloud into open space, with a second cloud hanging above him. Currents of air moved between the cloudy layers in direction frequently transverse to the current, below the lower cloud. He had repeatedly been carried along by this transverse current, and when upon coming down through the lower cloud, he had again been caught by the ascending current and whirled up again. Between the two clouds there were constant flashes of lightning from the upper to the lower. These flashes were not explosive. The heat lightning so often seen is the electricity of the upper cloud descending to the lower. The explosive discharges are always between the lower cloud and the earth. Between the two clouds hail is formed. The upper cloud is always less dense than the lower, and always less electrical.

A thunderstorm as it moved across the country was sometimes constantly renewed by the masses of vapor constantly ascending and carrying up electricity from the earth in diffused particles to be returned in explosive discharges. New vapor carried up new electricity. The French physicists thought that a thunder cloud might be disarmed by running up numerous prints; it might be disarmed or rendered harmless for a single [[totality?]], but as the clouds passed on new electricity would be sent up, so that to wholly disarm the thunder was impossible, for he had new resources always at command.

Mr. Wise had seen a water spout on one occasion that had no upper cloud, but was in the beginning of a single cloud of great density, which began to hang down in the centre, like a [[?]] hollowed into a whirlpool, carried round [[?]] tremendous rapidity, with discharges of lightning across it, and explosive discharges [[toward?]] earth.


The Daily Express
LANCASTER CITY, PA
SATURDAY EVENING, AUG. 11. 1860.

PROTECTION FROM ELECTRICITY.

We find in the current issue of that favorite journal, the Scientific American, an interesting paper from our townsman, John Wise, the interesting observations and practical suggestions of which will repay perusal. Mr. Wise's opinions in regard to the use of lightning rods conflict with the popular notions entertained on that question, but we have as yet seen no successful attempt by scientific men to dispute his theory. His observations in regard to the immunity of buildings covered with metallic roofs, when properly connected with the water-spouts, are undoubtedly correct ; and the best arrangement of this kind we have ever seen, is on the new railroad depot in this city. That building is covered entire with a metallic roof, from which several direct communications are made with the sewer, by means of the tin-spouting, and the iron pipes which convey the water from the roof into the sewer in the rear of the depot. Lightning would have no more effect in striking that building than it would have in coming in contact with a pond of water. It would be diffused over so large a surface, and so freely conducted off into the ground to the sewer, that one could be on the roof with perfect safety, when the bolt struck. It is on this principle that the lightning never does any damage in machine shops, press rooms, or other places where there is much iron, or on the railroad, where the electric fluid can be seen on a dark night during a thunder storm, dancing along the rails, and playing around the driving wheels of the locomotive, as harmlessly as so much phosphorescent matter shining in the dark.

We commend Prof. Wise's article to the careful perusal of all who feel an interest in this interesting topic:

THUNDER AND LIGHTNING

MESSRS. EDITORS: An article on "Atmospheric Electricity," published on page 73, of the present volume of the Scientific American, fully corroborates my own observations and experiments with electricity and lightning-rods. The theory of the lightning-rod is that it disarms the surcharged cloud which may hover over the building protected by the rod. Franklin and his contemporary electricians never claimed for the rod that it should receive thunderbolts. They claimed that the rod should carry lightning that the impending cloud to the earth silently. The rod is (theoretically) intended to draw the charge from the atmospheric magazine ; not to receive the red hot shot as fired from Jupiter's cannon. You are correct in saying that rods "do not cause a disruptive discharge when one would not have been made if the rod had not been erected." There should be no disruptive discharges upon a lightning rod that fulfills the office of its inventors, or else the experiment of the "thunder-house," as used to illustrate the nature and effects of atmospheric electricity in its silent as well as in its disruptive habitudes, means nothing. That the rod is a protection to an area of surface equal in diameter to four times the length of the rod's projection above the building is the practical truth of its efficacy, but not always, if at all, to thunderbolts ; it is only so when the surcharged thunder cloud comes within that distance of the point of the rod, that the electricity is silently conducted from the cloud to the earth. This does occasionally really happen. Mr. Daniel George, of Philadelphia (a practical manufacturer of electrical apparatus,) called my attention to the fact, one night, when a terrific thunder storm was raging over the city of Philadelphia. We went to the top of his building through a trapdoor ; the clouds were heavy, flying very low and surging violently around ; it was one of those thundergusts that inspire terror in those who are ignorant of electricity, and sublimity in the mind that contemplates it in an intelligent manner. The rod on this house had its point illuminated on that occasion. He informed me then that he only saw this illustration of the rod's efficacy when this kind of storms prevailed, and for that reason he invited me to the top of the building, knowing that I was always engaged in the construction of electrical apparatus at the time.

I have examined many lightning struck buildings that had lightning-rods on them erected as them erected as the theory of the rod directs. Now permit me to state, in all candor, the results of these observations. Some buildings were struck on the end of the roof or apex farthest from the end surmounted by the rod. The damage in these cases rather overbalanced the damage sustained in the cases where the rod received the bolt. In cases where the rod was struck, there was always a dispersion of the bold ; some run down the rod into the earth, rooting it up, and some of the bolts (electric fluid) would knock off shingles, shiver the end rafters of the building in others, knock off bricks from the top of the chimney, and sometimes knock to pieces the brick gable ends as though they had been struck by a cannon ball. Where it struck barns filled with grain and hay, the destruction by fire has been as fatal to the barns which receive the bolts on the rods, as the barns that received the bolts without the rods. In the latter case I have ever been confronted by the lightning-rod men with the allegation that the rod was not properly erected. In most cases I know that the rods were erected in accordance with the rule laid down, namely, the rod projecting above the building, contiguous in its length by screw joints, running into the earth six feet, with the lower points for distribution ; yet with all this the barn was burned down. A very small portion of disrupted lightning will set fire to a bar in the heat of summer, when a very heavy bolt will do no more to a dwelling-house than to knock off the shingles where it strikes, capsize the top of a brick chimney, knock in the gable apex of the wall and perform pranks through the interior of the house that puzzle all electrical and dynamical philosophy. Barns suffer the most, hereabouts, by thunderbolts. The reason is this. In warm weather, a barn stowed with hay or grain presents two favorable conditions for ignition and conflagration that do no exist in dwelling-houses and other building. The warm gases evolved from vegetable matter, like stacked and stored hay and grain, being both conducive and supportive to ignition and combustion, cause the greater fatality to barns. The hay or grain sometimes presents to the spark (sometimes intense scintillations of sparks from the exploded bolt) the same conditions presented in the knob of the "discharging rod" when cotton sprinkled with powdered resin, when we show the power of the electrical spark as drawn from the prime conductor of the electrical machine, in contradistinction to drawing the charge from it with a "pointed rod."

In the last case of my observations, only a few weeks ago, in this city, I made a close inspection of the dynamic character of the thunderbolt. In this case it struct a chimney (unsurmounted by a rod.) It was seen coming in an oblique direction. Its force upon the bricks, some two dozen of them, was similar to that in the case of any solid projectile coming in the same direction with an equal force. This indicated that a material body had struck the bricks, and struck them under the ordinary law of dynamical force.

My observations teach me that metallic-roofed houses are protected from injurious effects of lightning. In these, the greater security, I would advise a connection with the water conductor below, and the latter put into connection with a hydrant pipe or street gas pipe. Since our farmers are adopting the slate roof for barns, they also diminish the loss of barns by thunderbolt conflagrations. Upon slate roofs it glances off ; but upon shingled roofs there is a fuzz that is easy of ignition. Upon straw-covered (thatched) roofs there is, as it were, an invitation to Jupiter for a display of his pyrotechnics. And these conditions hold good, rod or no rod.

My observations on electricity, while sailing in and above the thunder cloud, corroborate the electrical theory of Professor Joseph Henry. When the rain drops come from a cloud, surcharged, as I know they are, with positive electricity, they are neutralized of their active electricity in two ways before they reach the earth, though they do sometimes 

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