32 



NA TURE 



\^Nov. II, iS86 



able information concerning the nature of this pheno- 

 menon at the moment of its occurrence. The locality in 

 which it was principally exhibited is near a station on the 

 South Carolina Railway, between Charleston and Summer- 

 ville, known as " Ten-mile Hill." It is thinly populated, 

 and almost entirely by negroes. Several persons who pre- 

 tended to have been eye-witnesses of the outburst gave 

 widely different testimony as to its character. According 

 to one account, the water and sand from one of the 

 " geysers " spouted to a height greater than that of a tele- 

 graph pole and continued to flow for four or five hours. 

 Another, and apparently an equally credible witness, de- 

 clared that the stream reached a height of six or eight 

 feet, and that the flow continued four or five minutes. 

 The latter statement is probably nearer the truth than 

 the former. 



A few instances of sand eruptions were found in the 

 city of Charleston, and a few also at Summerville, and at 

 the latter place water continued to flow from one of the 

 openings for several days after the first shock. 



It is important to observe that in no case was it found 

 that the water thus issuing from the earth was hot or 

 noticeably above the temperature of water in shallow wells 

 in the neighbourhood. Reports of boiling water having 

 been thrown up were very numerous, but no evidence that 

 the water was really hot appeared. The use of the word 

 " boiling " doubtless grew out of the appearance of the 

 water as it issued from the openings, and was probably 

 used by eye-witnesses to describe this appearance with no 

 reference whatever to temperature. 



There were also reports of the appearance of blue 

 flames in the neighbourhood of these eruptions, but no 

 reliable testimony to their existence could be obtained. 

 There was also a report that was circulated extensively 

 through the medium of the press of the country that two 

 or three showers of hot stones had fallen upon and near 

 the office of the CItarleston News and CouriiT. An ex- 

 amination of some of these shortly after they had fallen 

 forced the conviction that the public was being made the 

 victim of a practical joke. 



In the city of Charleston about forty lives were lost. 

 The greater number of casualties resulted from injuries 

 sustained by persons who were either in the street at the 

 time of the shock or who rushed out and were caught by 

 the falling deljris. No adequate description of the injury 

 to property can be gi\en in this place, and, indeed, the 

 results of this earthquke ha\e been so thoroughly con- 

 sidered in the public press that note is unnecessary. 



While there was probably not a single house in the city 

 which was not in some degree affected by the shock of 

 August 3r, there was naturally great diversity as to the 

 extent uf the damage in different localities. Some parts 

 of the city are built upon what is called " made land," 

 resulting in many cases from the filling up of old creek 

 bottoms and from other extensive levelling and grading. A 

 more careful study of these peculiarities and their distri- 

 bution may lead to the discovery of some relation between 

 local differences in structure and the areas of greatest 

 destruction. 



Unquestionably much is to be attributed to the difter- 

 ence in the character of the buildings themselves, and to 

 the relation of their lines of greatest or least strength to 

 the direction of the wave front. As was to be expected, 

 buildings constructed of wood suffered much less than 

 those of brick. The interior of wooden buildings, how- 

 ever, would often exhibit a scene of total destruction, 

 furniture, book-cases, &c., having evidently been moved 

 with great violence. A very brief examination of injured 

 buildings sufficed to establish, in a general way, the 

 principal direction of the movement, which was probably 

 in a north-west and south-east line. 



The probability of the destruction of a building depends 

 so largely on conditions other than the amplitude or direc- 

 tion of the vibration of the earth particle that the study 



of destroyed or damaged structures can yield little exact 

 information concerning these elements. The displace- 

 ment of bodies of simple form and structure, lying near to 

 or upon the surface of the earth itself, is a vastly more 

 reliable index of the direction and intensity of the dis- 

 turbance. In the churchyards of Charleston many 

 instances of displacement and overturned monuments, 

 columns, urns, &c., were found. These were examined 

 with some care, and a careful study of the results may 

 bring out some information concerning the dynamics of 

 the earthquake. A cemetery containing many pyramidal 

 or cylindrical shafts resting upon flat stone bases is toler- 

 ably certain, when disturbed by an earthquake, to exhibit 

 not only displacement but also instances of twisting about 

 a vertical axis ; cases of this kind were numerous at 

 Charleston. Such rotations by no means imply a similar 

 gyratory motion of the earth, as it is well known that they 

 may result, and doubtless]always do, from vibratory motions 

 in a single plane. It was not at all uncommon to find 

 two columns, very near to each other, twisted in opposite 

 directions. 



A table was given containing a rJsumJ of information 

 received at the office of the Chief Signal Officer from 

 regular observers of the Service and from a number of 

 voluntary observers. The place, time, supposed direction, 

 duration, and estimated intensity were given. Much dis- 

 crepancy is observable in the records of time. Con- 

 fusion is especially great in a few portions of the country in 

 which so-called " local time " is still adhered to. When- 

 ever "standard time" is known to have been used reduc- 

 tion has been made to that of the 75th meridian. In a 

 few cases, however, no reasonable supposition can explain 

 the discrepancies. Such records must be erroneous. 



A study of this column will show the great importance, 

 in making such observations, of determining the error of 

 the clock or watch at the earliest possible moment by 

 comparison with the time of some known meridian. It 

 must be said, however, that the extended use of standard 

 time has rendered these results vastly more accurate than 

 they otherwise would have been. Telegraphic time- 

 signals are now within the reach of most people, and 

 during the past two or three years a great improvement 

 in the accuracy of time-keeping among the people has 

 taken place. 



The direction of the movement recorded against each 

 station is that given by the observer. As it is based in 

 many instances on the motions of swinging objects, or 

 easily movable objects, it is of necessity often erroneous. 

 In the absence of correct instrumental records, however, 

 such observations are of value. The numbers expressing 

 the intensity of the disturbance were applied at this office, 

 from descriptions furnished by observers, according to a 

 scale adopted by the Director of the Geological Survey. 



This scale is as follows : — 



No. I. Very light. Noticed by a few persons ; not 

 generally felt. 



No. 2. Light. Felt by the majority of persons ; rattling 

 windows and crockery. 



No. 3. Moderate. Sufficient to set suspended 

 objects, chandeliers. iS:c., swinging, or to overthrow light 

 objects. 



No. 4. Strong. Sufficient to crack the plaster in 

 houses, or to throw down some bricks from chimneys. 



No. 5. Severe. Overthrowing chimneys and injuring 

 the walls of houses. 



With these intensity numbers an attempt has been 

 made to plot a chart of iso-seismal lines, or lines of equal 

 intensity. The result is shown in the chart. Nothing 

 short of the use of well-constructed seismographs can 

 furnish satisfactory measures of the amplitude of vibra- 

 tions of the earth particle or the maximum velocity of the 

 same, but in the absence of records of such instruments, 

 this chart, or a more perfect one constructed upon the 

 same plan, will afford opportunity for study. 



