« AnteriorContinuar »
which our newspapers have been teeming for many weeks pasi. We remained on the summit for some time, hoping for an opportunity to determine whether the explosions came from the east or west side of the mountain, or from the ground under our feet. As nothing occurred to settle this question, we descended the western slope to Mrs. Murphy's saw-mill, about eight miles from the head of Broad River. A portion of our party, who had passed two miles around the base of the moun. tain, heard three loud explosions, and felt two distinct shocks proceeding directly from the peak which we had left but one hour before. This I did not hear or feel, as I was engaged at the time in taking notes of the testimony of Mr. T. J. Dalton, amid the rumbling of machinery and the roar of the mill-dam.
It is unnecessary to give, in detail, all the testimony which we collected from the people while passing along the eastern and western side of this mountain, including a distance of eighteen miles. They all concurred in the following summary: That there were certain days marked by loud reports and severe shakes; that from fifty to seventy-five shocks have been felt since the 10th of February; that the noise begins with an explosion like a quarry-blast, followed by a rumbling sound, lasting only a few seconds; that the shocks are simultaneous, or almost so, with the reports, and seem to follow the direction of the rumbling sound, with this exception, that those near the top of the mountain assert they appear to be under and all around them ; that the reports all came from the Stone and Bald Mountain Ridge, those living on the east side pointing to the west, and those on the west pointing to the east for the direction of sounds; that these reports occur as often during the night as the day, in fair weather as in foul; that the effects are felt five miles on each side of the mountain-ridge, and extend from Broad River on the southwest to Catawba on the north, a distance of twenty-five miles; that houses shake, trees with their dead leaves tremble, glasses and crockery rattle, s havings in their workshops shake and "quaver," as one expressed it.
This testimony was collected from thirty or forty men and women of different degrees of intelligence, and their remarkable concurrence in the above statement places the facts beyond the possibility of doubt.
Several hypotheses have been proposed to explain these facts. One is, that the blasting of rock about the inouutains will account for all of them. Upon this point we made particular inquiry. There is certainly no operation going on about Stone Mountain, and as the work upon the tunnels in Swannanoah Gap has ceased for more than twelve months, there is no occasion for blasting anywhere else, as fine stones for building purposes, of every form and size, are scattered over all these regions. Besides, any one acquainted with the law of sound knows that the vibratory motion communicated to the matter in the crust of the earth by a blast (supposing it capable of extending to a great distance) will be felt much sooner than the undulations of the atmosphere, which transmit A person, therefore, standing a thousand yards from a quarry feels the trembling of the earth some time before he hears the sound of the blast. But in all these convulsions of the mountain the concurrent testimony is that the sounds and shocks are either simultaneous or nearly so. The blasting of rock, therefore, cannot account for this important fact.
Another hypothesis is, that these effects may be the result of electricity escaping from the mountain to the cloud, or descending from the cload to the mountain. There is nothing in the known operations of electricity to produce effects of this kind. Furthermore, these sounds and shocks occur as often in fair as foul weather; and the sounds are altogether different, as we had an opportunity of comparing them during our first night's stay upon the mountain. Electricity never explodes unless it meets with a bad conductor, and as the mountain affords it an easy transit, the explosion must take place somewhere between the summit and the cloud, or along the line of its pathway. The explosion, therefore, being in the air, must be subject to the same laws of sound as the blast of the quarry, and the same method of reasoning will apply in this case as in the other.
The simultaneousness of the shocks and explosions proves that the sound has not far to travel through the air to reach the observer; and while the primary cause of the explosions may be deeply seated in the earth, yet the immediate cause of the sounds may be at or near the surface. It is known that the loudness and intensity of sounds depend upon the amplitude of the sound-wave. Suppose, then, that the cause of these explosions be deeply seated in the crust of the earth, the force acting and reacting upon the superincumbent strata will impart its vibrations to them and transmit through them its impulsions to the atmosphere above.* I am inclined, therefore, to the opinion that most of the noises accompanying earthquakes are the results of vibratory movemeuts in the earth's crust, or are the secondary effects of a force acting at great depths beneath. This opinion seems to be sustained by the evidence of the witnesses upon the summit as well as five miles from the base of Stone Mountain, all of whom concur as to the simultaneousness of the shocks and explosions. To this it may be objected that earthquake-shocks are often unaccompanied with noises, or that the former may precede the latter by several minutes. In reply, I will state that the crust of the earth is composed of different strata, some capable of transmitting vibrations that are audible and others that are not, as a string may be made to vibrate and yet produce no audible sound. Now, suppose our observer to be standing upon a section of the earth's crust which is incapable of receiving or imparting sound vibra
* This explanation is undoubtedly correct; the velocity of the sound-wave in the earth is the same as that of the wave of percussion; or, in other words, the two are identical. An car, therefore, placed at the surface of the grourd would at any point hear a sound simul. taneously with the shock. J. H.
tions, he may feel the earthquake-shocks and yet bear no noise; or, if sounds should reach him after an interval of time, they may come from a distant section capable of producing them, but which must be transmitted to his ear through the intervening atmosphere.
This discussion leads me to the conclusion that the phenomena connected with the agitation of Stone Mountain must be referred to that general volcanic or earthquake force, which seems as necessary to the economy of nature as light, heat, or electricity. I am not bold enough to venture a theory sufficiently broad to explain these peculiar phenom. ena. I cannot penetrate the earth to examine the configuration of its inner surface. There may be broad and high arches under which the earthquake-ware may move without disturbing, the crust above; or there may be deep depressions presenting walls, against which the molten tide may beat and break and send up its thundering vibrations to the summit of the loftiest mountain. All this is hypothetical and unsatisfactory. But although we are not sufliciently acquainted with the nature of this force, its modes of action and the laws which govern it, to suggest a theory capable of explaining all the phenomena, yet we may examine the facts with reference to the probability of Stone Mountain becoming an eruptive volcano. While the explosive character of the sounds, simultaneousness of sounds and shocks, and the limited area of agitation seem to indicate some local cause, yet the general rule which regulates the distribution of volcanoes on continents seems to militate against such a conclusion. Volcanoes are arranged along the border regions of continents, as between the Pacific and Rocky Mountains, on islands of the coast, or oceanic islands. They are generally confined to the borders of larger oceans and are seldom found in the interior of continents. There are none in America east of the Andes and Rocky Mountains, and no remains of volcanic action have ever been found along the Appalachian range. These are important facts, indi. cating no chance results, but pointing to a natural law which regulated their geographical distribution. And when we consider, too, that volcanoes, with but few exceptions, are only a few miles from the sea or lake; that the Blue Ridge, of which Stone Mountain is only an append. age, is two hundred and fifty miles from the Atlantic, and presents no inarks of former eruptive action, we cannot believe that in these latter days it will behave itself unseemly and do violence to that natural law which planted it in the garden-spot of the South, and gave to the Carolinas the grandest, loveliest scenery on the Appalachian range.
(The following suggestions may be considered as a possible solution of the phenomena in question : It is a well-established fact in geology that the surface of the earth has undergone and is undergoing changes. The highest mountain-chains have been in past geological periods beneath the surface of the sea, as is evident from the marine shells which are found in their strata. It is also well established that some portions of the earth's surface are at present gradually rising and others slowly falling. Now, if we assume that the region around Stone Mountain is undergoing a very gradual elevation or depression, then it will follow that the rocky strata will be brought into a condition of stretching or tension which will go on until the limit of elastic cohesion is reached, when a rupture or crack will suddenly take place which must be attended with a jar, and, in some cases, with an audible sound. If the rocky strata is of the same material from the surface down into the interior; for example, granite, and the mountain being in the process of depression, the crack will take place deep in the interior. If, on the other hand, the mountain is being elevated, the crack will be at the surface. If, however, the upper strata are more extensible than the deeper seated, the crack may be in the interior in the case of an elevation as well as in that of a depression.
It has of late years been suspected, from the discrepancy in later and older measurements of points on the Andes, that this mountain system is in a state of very slow subsidence.
If the foregoing views are correct there is no indication of a volcanic outburst; and whatever moral effect the disturbances may have on the character of the inhabitants of the region, there is little danger as to any physical changes taking place of sufficient intensity to endanger life.-J. H.)
REPORT ON THE TRANSACTIONS OF THE SOCIETY OF PHYSICS
AND NATURAL HISTORY, OF GENEVA, FROM JUNE, 1872, TO JUNE, 1873.
By PROF. A. DE LA Rive, PRESIDENT.
[Translated for the Smithsonian Institution. ] GENTLEMEN : Called a second time, through your kindness, to preside over you, again I have the honor to present the annual report of such of your transactions as your president has considered it desirable to register. Happily, this year, that part of the report appropriated to biographical notices is extremely brief. The society, after the great losses it sustained during last year, has not this year been called to mourn a single one of its ordinary regular members. But of its honorary members two have been taken away, Madame Somerville and Arnold Escher de la Linth.
I have little to say of Madame Somerville, who has made for herself a brilliant reputation, during the last fifty years, by her mathematical works, and especially by her translation into English of the Mécanique céleste of Laplace. She was in full sympathy with the different branches of science, and well informed as to their progress.
She had for several years resided in Florence, where she died at an advanced age.
Arnold Escher de la Linth was a son of the celebrated Courad Escher, surnamed de la Linth on account of the great service he rendered to the valley of that name, by directing the river Linth into Lake Wallenstadt, in order to protect the valley from inundations; an admirable work, managed with great talent and perseverance.
Arnold Escher acquired at an early age, under his father's tuition, love for the natural sciences. Conrad Escher was in fact one of the most eminent naturalists of his time; his observations in regard to the dispersion of erratic bowlders, and their distribution over the Swiss plains, are especially remarkable.
The son, during the frequent excursions made with his father into the mountains of Glaris, formed the conception of a geological map of Switzerland, which he afterward executed and published, in concert with M. Studer, the eminent geologist of Berne, after twenty years of labor and innumerable journeys. He examined the Alps in every detail, and the precision and justice of his judgment, the accuracy of his observations, and the quickness of his comprehension permitted him to accumulate more abundant material for study than unfortunately he could make use cf.
The desirable qualities we have mentioned inspired confidence, and he was frequently consulted ; his answers were always characterized by