636 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



On the other handjLj^ell shows very beautifully, how the grad- 

 ual upheaval and depression of the land could have produced, and 

 is producinjT, very great changes in climate, making some portions 

 of the earth cooler and others warmer. Hence the changes in 

 climate which have taken place in some portions of the earth, are 

 uo proof that the earth is a cooling body. 



That the phenomena of earthquakes, volcanic eruptions, gey- 

 sers and hot springs, are local, observation has conclusively shown. 

 That they cannot be attributed to a molten mass underlying the 

 whole surface of the earth, is almost a necessary conclusion there- 

 from. 



Lyell believes, that the substances emitted from volcanoes, 

 geysers and hot spings, exist in large subterranean masses, and 

 that earthquakes are caused by their movements. 



Man}' districts, such as southern France, are filled with extinct 

 volcanoes. If the earth's interior is a molten mass, from which 

 the substances emitted from volcanoes are drawn, Avhy has any 

 volcano ever become extinct ? Upon Lyell's theory, the explana- 

 tion is, that the sea or lake from which they were supplied, has 

 been exhausted. 



The idea that granite and other pi u tonic rocks are the oldest 

 <reoloo-ical formations, and were therefore the first solid surface of 

 the earth, is a strong support to La Place's theory, but Hutton 

 and Lyell have shown that these rocks vary in age, and are in 

 many cases of a much later formation than the rocks and strata 

 underlying them. They have shown that these rocks, 'like all 

 others, are continually forming, and are in all probability never 

 produced except under, and, therefore, after, the formation of 

 overlying strata; since wherever plutonic rocks are found, the 

 adjoining and overlying strata are greatly disturbed; some are 

 converted into metamorphic rocks, and in many cases veins and 

 runners are found projecting from the mass of the rock into the 

 gurroundinnf strata. 



The -cause of earthquakes, volcanic eruptions, geysers, and the 

 formation of plutonic rocks, cannot be given until sufKcient data 

 have been obtained for its explanation. Simply as an hypothesis 

 submitted to the test of observation, I suggest that the depression 

 which certain districts of the earth is undergoing is the cause of 

 these movements; that not only are volcanic eruptions and the 

 formation of plutonic rocks due to the same cause and the same 

 masses of liquid matter, but that when plutonic rocks are formed 



