SCIENCE.-SUPPLEMENT. 



FRIDAY, MAY 20, 1887. 



ABSTRACT OF THE RESULTS OF THE 

 INVESTIGATION OF THE CHARLESTON 

 EARTHQUAKE.' 



The amount of information now in possession 

 of tbe U. S. geological survey, relating to the 

 Charleston earthquake, is very much larger than 

 any of similar nature ever before collected relating 

 to any one earthquake. The number of localities 

 reported exceet^s sixteen hundred. The sources 

 of information are as follows : 1°, we are deeply 

 indebted to the U.S. signal service for furnishing 

 us the reports of their observers ; and, 2°, equally 

 so to the Lighthouse board, which has obtained 

 and forwarded to us the reports of keepers of all 

 lighthouses from Massachusetts to Louisiana and 

 upon the Great Lakes ; 3°, to the Western union 

 telegraph company, which instructed its division 

 superintendents to collate and transmit many val- 

 uable reports ; 4", to the Associated press, which 

 has given us access to the full despatches (with 

 transcripts thereof) which were sent over the wires 

 centring at Washington during the week follow- 

 ing the earthquake ; 5^, to geologists and weath- 

 er-bureaus of several states, who have kindly ex- 

 erted themselves in this matter, and collected 

 much important information ; 6°, to a considera- 

 ble number of scientific gentlemen who have 

 distributed for us our circular letters of inquiry in 

 special districts, notably. Profs. W. M. Davis, C. 

 G. Rockwood, J. P. Lesley, T. C. Mendenhall, and 

 Messrs. W. R. Barnes ©f Kentucky and Earle 

 Sloan of South Carolina ; 7**, to a large number of 

 postmasters in the eastern, central, and southern 

 states ; and, finally, to hundreds of miscellaneous 

 correspondents throughout the country. 



In collecting this information, a printed list of 

 questions was prepared. This practice has been 

 resorted to in Europe and in Japan with consider- 

 able success, and the questions which have been 

 devised for distribution in those countries have 

 been prepared with great skill by some of the 

 ablest investigators of earthquakes. Prof. C. G. 

 Rockwood of Princeton has also been in the habit 

 of distributing formal questions of this character 

 in this country whenever apprised by the news- 

 papers of a notable shock. Availing ourselves of 



1 Read before the National academy of sciences at 

 Washington, April 19, 1887. 



his advice and assistance, questions prepared by 

 him were printed and widely distributed. They 

 were much fewer and more simple than those em- 

 ployed in Europe, because European investigators 

 depend almost wholly upon the educated classes 

 to answer them, while in this country the unedu- 

 cated but intelligent and practical classes of the 

 people must be the main reliance. These ques- 

 tions were designed to elicit information, \°, as to 

 whether the earthquake was felt ; 2°, the time of 

 its occurrence ; 3*, how long it continued ; 4°, 

 whether accompanied by sounds ; 5°, the number 

 of shocks ; 6°, general characteristics which would 

 serve as a measure of its intensity, and indicate 

 the kind and direction of motion. 



It is to be observed that the only information 

 to be hoped for, which can have even a roughly 

 approximate accuracy, is the time of transit of 

 the shock. The degree of approximation in the 

 time data actually obtained will be adverted to 

 later. Special effort was made to obtain informa- 

 tion as to the relative intensity of the shocks in all 

 parts of the country. At the very outset a serious 

 difficulty presents itself. In the estimates of in- 

 tensities there is no absolute measure. What is 

 really desired is some reliable indication which 

 shall serve as a measure of the amount of energy 

 in any given portion of the wave of disturbance as 

 it passes each locality. The means of reaching 

 even a provisional judgment are very indirect, and 

 qualified by a considerable amount of uncertainty. 

 To estimate the force of a shock, we have no better 

 means than by examining its effects upon build- 

 ings, upon the soil, upon all kinds of loose objects, 

 and upon the fears, actions, and sensations of 

 people who feel it. In view of the precise meth- 

 ods which modern science brings to bear upon 

 other lines of physical research, all this seems 

 crude and barbarous to the last degree. But we 

 have no other resource. Even if it were possible 

 to obtain strictly comparative results from such 

 facts, and decide with confidence the relative 

 measure of intensity which should be assigned to 

 each locality, we should have gained measures 

 only of a series of local surface intensities, and 

 not of the real energy of the deeply seated wave 

 which is the proximate cause of the surface phe- 

 nomena. Notwithstanding the indirect bearing 

 of the facts upon the real quantities we seek to 

 ascertain, and their apparently confused and dis- 

 tantly related character, they give better results 

 than might have been supposed. When taken in 



