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battleships and cruisers for the existing steam boilers and engines, the saving in cost of coal would not be less than $1,000,000 per annum, or, what would be of far greater importance, the distance traversed by each ship without recoaling would be more than doubled.”

Referring to the question of ship propulsion, we find that for gas engines the weight and space employed is much less; service of men in hot, stilling, damp engine and fire rooms is avoided; the number of men is greatly reduced and their physical stamina kept at the highest point; they burn far less fuel and do away with smoke by day and sparks by night.

Commander A. B. Willetts, United States Navy, summarizes the advantages as follows:

No boilers
No pipe lines under pressure
No smoke
No ashes
No coaling-ship distresses
No stoking furnaces
No condensers to keep tight
No forced-draft blowers
No fuel cost or delay in getting up steam
No fuel cost for keeping fires for "standing by"

Before touching upon the future, the humanitarian side of the gas versus steam engine merits notice: The physical tax upon the workers who must stoke, handle ashes, oil, and look out for the integrity of boilers and long lines of pipes under pressure, with the accompaniment of heat and dirt, saps their vitality and shortens their lives. Such conditions being absent from the gas-engine plant, the men are always in condition to render intelligent and useful service.

A visit to the basement world of one of our large cities presents an inferno only to be painted by a modern Dante. Accidents are constantly occurring with steam, especially as the competition of modern life demands greater service on lesser margins. Disastrous accidents that can not be hidden are made known, but think of the unchronicled happenings.

The United States uses about 100,000,000 tons of coal in its manufactures. The saving of half of this vast coal pile will not only benefit every calling, profession and trade in the cost of production, but will cheapen the cost of the remaining 300,000,000 tons used.

According to the Census the United States now uses about 15,000,000 horse-power, and this will in all probability be doubled in the next ten years. Fully one-third of this increase will be in the form of gas engines. Blast furnace owners, realizing the power thrown away, will begin to utilize them far more universally than at present.

Gas-producer engines and oil engines may now be seen by the hundreds in Palestine, replacing the water-wheels that have been used there for centuries, and orders are being given for such engines throughout the world generally.

The waning strength and stiffening joints of advancing years of farmers, fishermen and mechanics will find in the simple and adaptable gas engine a means to prolong earning power and life itself.

For large pumping or generating plants for lighting or traffic, the gas engine, using gas from coal or crude oil, will be used.

For the multifarious uses of modern needs, requiring handy portable motors, liquid primary fuels will be used, such as gasolene and alcohol.

The extreme South will find a new field of profit, rivaling that of cotton, in the raising of cassava for alcohol, just as soon as the people demand true "free manufacture" of alcohol.

For suburban railways the simple-unit, independent car, gaspropelled, will drive out all others.

As a conclusion, I predict that soon all towns using in the aggregate 2000 horse-power will have central gas-power plants furnishing power for municipal and private use at a minimum of cost, because for such power, and upward, the by-products recovered will enable gas to be delivered to the engine free of cost.

I regret that my engagements are not such as to permit me to be present so that I could advance perhaps more radical ideas and be prepared to sustain them, but send this message to the electricians assembled:

Link electricity with the gas engine and you will produce a new chariot of world-wide conquest, whose victories in the next decade will cause the great achievements of the past ten years to fade into insignificance.

THE PRESIDENT: There is no subject before the industry at this time that is of more interest than the subject of gas engines. I suggest that a vote of thanks be passed to Mr. Bibbins and Mr. Nixon for their very interesting papers. Mr. Nixon is not a member of the association, and he has spent a great deal of time in preparing this paper.

MR. BURNETT: I make a motion to that effect, Mr. Chair

man.

(The motion was seconded and carried.)

THE PRESIDENT: We shall now have the honor and pleasure of listening to an address by Dr. Steinmetz, on Lightning and Lightning Protection.

Dr. Steinmetz then delivered the following address :

LIGHTNING AND LIGHTNING PROTECTION

LIGHTNING PHENOMENA IN THE CLOUDS

The first man who attacked the problem of lightning and lightning protection, a century and a half ago, was our great citizen Benjamin Franklin. He gave us the lightning rod, which is now universally recognized as the most effective and only protective device for isolated points, as steeples, chimneys, and so forth. The next step in advance was made by Faraday. He showed that in the interior of a perfectly conducting body no electric disturbances can be produced by outside electric forces. This led to the most effective protection possible against lightning or electric disturbances, the use of a grounded metal cage —“Faraday's cage"-enclosing the structure to be protected, whether a building against lightning, or a delicate instrument against electric fields.

In its simplest form, Faraday's cage, applied to a transmission line, is the ground wire above the line, and the protection afforded by it is the more complete, the more the overhead ground wires represent the condition of an enclosing cage of perfect conductivity. That is, a system of wires above and on the sides of a transmission line is superior to a single wire, a wire of high conductivity superior to a small iron wire. Here I specially desire to draw attention to the second requirement of the Faraday cage, high conductivity. It is not sufficient merely to have any kind of overhead grounded wire regardless how small, but high conductivity of the grounded conductor is essential in many cases of atmospheric disturbances.

In the last ten years, transmission voltages have crept higher and higher, transformers have been built, of considerable size, of still higher voltages, so that exact data on the action of voltages up to 300,000 are now available, and approximate data for potentials above a million volts. It was found that air has a definite and fixed breakdown strength; that is, just as a beam breaks mechanically as soon as the stress in it exceeds a definite value, the breaking strength of the material, so air breaks down by a disruptive spark as soon as the electric stress in the air, or the potential gradient, exceeds a certain value, which is about 100,000 volts per inch. The disruptive strength of air is, over a wide range, proportional to the pressure; that is, at two atmosphere pressures it is twice as high, or 200,000 volts per inch, at one-quarter atmosphere it is one-quarter, or 25,000 volts per inch.*

The striking distance in air between needle points has been investigated up to 300,000 volts, and found that for high voltages it is very nearly 10,000 volts per inch, that is, a discharge of 30-inch length between needle points requires 300,000 volts. If between two needle points the potential difference is gradually increased, already at relatively low voltages, the disri ive strength of the air at the needle points is exceeded, the air at the points breaks down and becomes conducting and luminous, as "brush discharge," so that the terminals are not needle points any more, but the whole space, of approximately spherical shape, that is covered by the brush discharge. As result thereof, for high voltage, no appreciable difference exists in the striking distance between needle points and between spheres the centres of which approximately coincide with the needle points, so long as the diameter of the spheres is small compared with their distance. With increasing potential difference between needle points, the brush discharges spread out against each other until only about 40 per cent of the space between the needle points is free, and then a disruptive spark passes.

Naturally, as soon as determinations of spark voltages became available, attempts were made to estimate the voltage of a lightning flash. Consider in a lightning flash the discharge as that in an ununiform field, similar to that between needle points, and so requiring about 10,000 volts per inch. In this case, a lightning flash of two miles, or about 10,000 feet in length, would require a potential difference of about 1200 million volts. The existence of such voltages in the clouds does not appear possible: a potential difference of 1000 million volts would produce a brush discharge of about one-half mile in length before the final lightning flash occurred. In the brush discharge the air is electrically broken down, and conducting.

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*Only at very low pressures, where the distances between air molecules becomie appreciable, this law ceases, and the disruptive strength increases again, and seems to become infinitely great in a perfect vacuum.

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