1886.] NEW YORK ACADEMY OF SCIENCES. 19t 



quakes/' which one correspondent seriously gives me, 1 ac- 

 knowledge it as apart of my duty to satisfy, as far as I am able, 

 the demand which has been made by the public. I shall, there- 

 fore, present a brief review of what is known and believed in 

 regard to the phenomena and causes of earthquakes, by those 

 whose opinions on this subject are most worthy of confidence. 



There is something particularly unsettling and terrifying in 

 the upheavals and undulations of what we call terra firina, be- 

 cause it has been accepted as the type of stability. To men of 

 all countries and ages, civilized and savage, the earthquake has 

 been a peculiar terror and mystery. Even the most stoical and 

 reasonable have lost their self-possession when they have felt 

 the solid earth heaving and groaning beneath them; and in the 

 countries where earthquakes are most common, the horror and 

 dread they inspire are never lessened by familiarity, but every 

 new shock produces fresh and increased alarm. It is not sur- 

 prising, then, that in a region like Eastern North America, 

 which has been supposed to be exempt from serious catastrophes 

 of this kind, the occurrence of such an event as that which re- 

 cently took place at Charleston, has produced a profound and 

 widespread sensation. It has not only called out strong ex- 

 pressions of sympathy with the sufferers, but has excited the 

 keenest desire to know all that can be known of this and similar 

 phenomena. It has been the common subject of conversation 

 throughout the land. The journals have been full of descrip- 

 tive details. Scientists of all kinds have been interviewed, and 

 been made to give their views, if they had any; if not, they 

 have been supplied to them. As a consequence, many wild and 

 contradictory statements have been made, and so many theories 

 advanced, that the public has hardly known what to believe. 



Yet earthquakes are neither novel nor mysterious, but are 

 among the most common and simple of terrestrial phenomena; 

 they have certainly recurred at frequent intervals throughout 

 all geological time of which we have any record, and it is prob- 

 able that now, not an hoar, perhaps not a minute, passes, but 

 more or less violent vibrations take place somewhere on the 

 earth's surface. In later years, earthquakes have been carefully 

 studied in many countries by geologists and physicists, and the 

 conclusions reached have been so generally harmonious that 

 there is now very little difference of opinion as to their cause, 

 and the manner in which this cause operates. 



Briefly told, an earthquake, is a movement caused by a shrink- 

 ing from the loss of heat, of the heated interior of the earth, and 

 the crushing together and disijlacement of the rigid exterior as it 

 accommodates itself to the contracting nucleus. 



I cannot, in the limited space now at my disposal, give any- 



