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SOME PHENOMENA OF SOUND.

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Duane's experiments, and his own, some of which were made in company with Sir Frederick Arron and Captain Webb, Her Britannic Majesty's Navy, both of the British Light House Establishment, who were sent here to study and report on our fog signal system, formulated these abnormal phenomena. He said they consisted of

"1. The audibility of a sound at a distance and its inaudibility nearer the source of sound.

"2. The inaudibility of a sound at a given distance in one direction, while a lesser sound is heard at the same distance in another direction.

"3. The audibility at one time at a distance of several miles, while at another the sound can not be heard at more than a fifth of the same distance.

"4. While the sound is generally heard further with the wind than against it, in some instances the reverse is the case.

"5. The sudden loss of a sound in passing from one locality to another in the same vicinity, the distance from the source of the sound being the same."

In illustration of the foregoing the following is cited: "There are six steam fog whistles on the coast of Maine; these have been frequently heard at a distance of twenty miles, and as frequently can not be heard at the distance of two miles, and this with no perceptible difference in the state of the atmosphere.

"The signal is often heard at a great distance in one direction, while in another it will be scarcely audible at the distance of a mile. This is not the effect of wind, as the signal is frequently heard much farther against the wind than with it; for example, the whistle on Cape Eliza

beth can always be distinctly heard in Portland, a distance of nine miles, during a heavy north-east snow storm, the wind blowing a gale directly from Portland toward the whistle."*

In illustration of his sound-wave theory, Professor Henry states the following, as given in the same paper:

"It frequently happens on a vessel leaving a station that the sound (of the fog whistle) is suddenly lost at a point in its course, and, after remaining inaudible some time, is heard again at a greater distance, and then is gradually lost as the distance is further increased. This is attributed to the upward refraction of the sound-wave, which passes over the head of the observer, and continues an upward course until it nearly reaches the upper surface of the current of wind, when the refraction will be reversed, and the sound sent downward to the earth. Or the effect may be considered as due to a sound - shadow produced by refraction, which is gradually closed in at a distance by the lateral spread of the sound-wave near the earth on either side, in a direction which is not affected by the upper refraction. Another explanation may be found in the probable circumstance of the lower sheet of sound-beams being actually refracted into a serpentine or undulating course."

Upon this sound-wave theory, Mr. Johnson, also said: "This ricochetting of sound, these intervals of audibility, ought to be recognized by the mariner, who should now understand that in sailing toward or from a fog-signal

"Aberrations of Audibility of Fog Signals." A paper read before the Philosophical Society of Washington, October 22, 1881, by Arnold B. Johnson, Chief Clerk of the Light House Board.

OTHER EXAMPLES AND PRINCIPLES.

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in full blast, he might lose and pick up its sound several times though no apparent object might intervene. And the mariner now needed that science should deduce the law of this variation in audibility and bring out some instrument which should be to the ears what the mariner's compass is to the eyes, and also that variations of this instrument yet to be invented, be provided for and corrected as now are the variations of the mariner's compass. The speaker referred to the benefit the mariner had derived from the promulgation of Professor Henry's theory of the tilting of the sound-wave up or down by adverse or favorable winds, and said that by this the sailor had been led to go aloft in the one case and to get as near as possible to the surface of the water in the other, when trying to pick up the sound of a fog-signal."

Such are the explanations given of these phenomena by these eminent scientists. The facts are exceedingly interesting and are worthy of investigation.

CHAPTER XII.

GETTYSBURG, THE NATION'S SHRINE.

"On Fame's eternal camping ground
Their silent tents are spread,

And Glory guards, with solemn round,

The bivouac of the dead.”

S soon as the result of the series of engagements between the Federal and Confederate armies at Gettysburg was known throughout the country, people from all sections flocked to that place. In traversing the field of conflict the evidences of the tremendous struggle were visible in all directions. Disabled cannon, abandoned and captured arms, broken down fences, trampled and ruined fields of grass and grain, pools of blood, dead and wounded men, and the bloated and offensive carcasses of horses, were some of the visible results. The hearts of patriots were saddened and their feelings shocked to see the remains of the brave men who had yielded up their lives that the Nation might live, because of the necessary haste with which they were interred, in many instances but partially covered with earth. These partly covered bodies were scattered for miles over ground that would soon be cultivated. The graves which were marked were only temporarily so, and the marks would soon decay or be obliterated, and all traces of the sacred

ORIGIN OF GETTYSBURG CEMETERY.

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dust be entirely lost. Humanity shuddered at the sight, and patriotism revolted at such desecration. The idea then was suggested of purchasing a suitable piece of ground upon some elevated place, and gathering these men from all parts of the field and decently interring them side by side. Mr. David Wills, a citizen of Gettysburg, submitted a proposition to effect the purpose to his Excellency, Governor Andrew G. Curtin, in a letter dated July 24th, 1863; and the governor, with the promptness and zeal for the cause of the Union, and the welfare and comfort of the soldiers, which he had always shown, approved of the design, and appointed Mr. Wills as agent to carry out the project. Mr. Wills at once opened correspondence with the governors of other states, which had soldiers dead upon the field, and they all with great promptness responded and seconded the plan. About seventeen acres of ground on Cemetery Hill, at the apex of the triangular line of battle of the Union army, was purchased and the title made to the State of Pennsylvania. No more beautiful or appropriate place for the gallant heroes who died upon that field, could be found than the one selected. It is high and prominent. It was the center of the Federal position. Upon it were planted the batteries which thundered forth death and destruction to the foe; and it was there that the awful fire of Lee's one hundred and twenty guns was concentrated during that fearful two hours' artillery duel, which preceded Pickett's great, but wild and disastrous charge. Lots in this cemetery were gratuitously given to each State having dead on the field. It was arranged that the expenses for the removal and re-interment of the dead, the laying out, orna

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