3 oo POPULAR LECTURES AND ADDRESSES. 



eruptions, we know that there is sometimes, and 

 that there may be always, some liquid in the 

 earth's interior. How much liquid there may 

 be how much it is necessary to assume in order 

 to account for the known phenomena of volcanic 

 eruptions cannot be estimated with any degree 

 of definitencss ; but I hope to be able to put before 

 you, this evening, arguments which will convince 

 you that we cannot admit that there is any great 

 liquid ocean under the earth's surface, and that we 

 are forced to look to local causes for the explan- 

 ation of volcanic eruptions. 



The main reason given for supposing the 

 interior of the earth to be fluid is not, however, the 

 existence of volcanic phenomena. From consider- 

 ations regarding underground temperature, many 

 geologists have been led to hold as a geological 

 truth that the interior of the earth is molten 

 throughout. 



The evidences of a high internal temperature 

 arc well known. It is found by observation that 

 passing downwards from the surface, we meet first 

 with a thin stratum in which variations of tempera- 



