Nov. II, 1886] 



NA TURE 



T' 



once or twice at intervals of two hours. The faikire of 

 Dr. Frisch, of Vienna, in experiments of this kind is due 

 to the slow process of vaccination adopted by him. Suc- 

 cess can be secured only by the rapid method here 

 described. The immunity conferred under such condi- 

 tions is the best proof of the e.Kcellence of this method. 



REPORT ON THE CHARLESTON 

 EARTH(2UAKE^ 



'HE earthquake of August 31, which, from the locality 

 in which its greatest power was displayed, will 

 generally be known as the" Charleston Earthquake," was, 

 perhaps,' the most notable disturbance occurring within 

 the limits of the United States of which we have any 

 knowledge. It is entitled to this rank both on account of 

 the wide area over which it was distinctly felt, and of 

 the magnitude of the disaster which it caused in the 

 immediate vicinity of the point of maximum intensity. 



The earthquake consisted of a series of seismic dis- 

 turbances which began in slight but distinctly noticeable 

 tremors occurring on August 27 and 28, at the town of 

 Summerville, about twenty-five miles north-west of 

 Chaileston, South Carolina. 



The shock of greatest violence occurred a little before 

 ten o'clock on the night of Tuesday, August 31. It was 

 followed by several of lesser magnitude on that night, and 

 during the succeeding three or four weeks. The great 

 shock began in the city of Charleston within a few 

 seconds of 9.51 p.m., 75th meridian time. The duration 

 of the vibratory motion of the earth at that point was 

 probably about forty seconds ; the motion at first 

 being moderate, but increasing with great rapidity during 

 the last ten or fifteen seconds. 



All of the loss of life and property during the whole 

 series of disturbances is to be attributed to this first 

 shock. Five minutes later another occurred, and ten 

 minutes later still another ; the latter being of con- 

 siderable violence, but neither alone would have done 

 any damage. The same may be affirmed of the succeed- 

 ing series of disturbances, which, with greatly diminished 

 intensity and at increasing intervals of time, continued to 

 maintain the conditions of alarm and terror into which 

 the people of the afflicted locality were naturally thrown 

 by the first disturbance. Although some injury to build- 

 ings resulted from these after shocks, it is tolerably cer- 

 tain that in all such cases displacement and fracture had 

 taken place in the great shock ; the lesser disturbances 

 simply finishing what had then been nearly completed. 



The origin of the disturbances, appears to have been 

 somewhere below a point fifteen or twenty miles north- 

 west of Charleston ; that is, in the neighbourhood of the 

 town of Summerville. A chart of provisional co-seismal 

 lines drawn by Mr. Hayden of the Geological Survey, 

 and published in Science for September 10, seems to 

 locate this centre somewhat further north than the point 

 indicated above. At the time of its construction, how- 

 ever, information from many points was lacking, and 

 that which was at hand was admittedly doubtful in some 

 degree. 



Reference is made later to the iso-seismal chart which 

 accompanies this Report, and which indicates that the 

 origin was near the point referred to above. Strong proof 

 of this is also furnished in the intensity and character of 

 the disturbance as shown by the effects which were still 

 visible when an examination was made a few days after the 

 principal shock. The appearance of the brick piers upon 

 which many houses in Summerville rest was such as to 

 justify the conclusion that the principal component of the 

 motion at that point was vertical, and it was evident that 

 the destruction of buildings was much less than would 

 have resulted from a horizontal movement equal to that 



' By Prof. T. C. Mendenhall, Assistant. Fro;n the Monthly IVeathcr 

 R€i':c-M, U.S. Signal Serv.ce, August i8S6. 



which had taken place in Charleston and elsewhere in 

 the neighbourhood. 



Another fact of importance is that in the vicinity of 

 Summerville the disturbances preceding that of August 31 

 took place, and here they have been most numerous and 

 most persistent. Indeed, at the present writing, nearly 

 a month after the first perceptible shock, they still occur 

 at irregular intervals varying from a few hours to a few 

 days. Only the most violent of these have been felt as 

 far as Charleston. 



Nearly all the movements in Summerville and vicinity 

 have been accompanied by, and, indeed, generally pre- 

 ceded by, a low rumbling sound, lasting one or two 

 seconds, and not unfrequently this sound, always un- 

 mistakable in its character, was neither accompanied nor 

 followed by a perceptible movement. This was a com- 

 mon occurrence at Summerville and in the immediate 

 vicinity, and it was found that among several observers 

 there would be no agreement upon the direction from 

 which the sound appeared to come. 



At a distance from ten to fifteen miles from Charleston 

 in the direction of Summerville some of the most curious 

 and interesting effects of the disturbance were to be seen. 

 These were the " sand craters" and crevices, out of which 

 extensive eruptions of sand and water had taken place 

 on the night of August 31. The craters thus formed 

 varied in size from an irregular oval, twenty-five feet long 

 by fifteen feet wide, to shallow cones not over an inch in 

 diameter and beautifully symmetrical in form. The area 

 surrounding these openings was generally flooded with 

 s'and, often acres in extent, to a depth varying from a 

 fraction of an inch to fifteen and eighteen inches. About 

 the larger cavities the average depth was probably not 

 less than six inches, and the area covered often an acre or 

 more. The flow of sand was unquestionably only an inci- 

 dent to the outflowing of vast quantities of water, the 

 greater part of which disappeared within a few hours after 

 its appearance. The few crevices or " cracks " in the 

 earth which were found were in character and origin 

 similar to the " craters," being long and narrow openings, 

 through which water with sand had been ejected. 



It was difficult, in fact quite impossible, to obtain reli- 



