284 M. L. Cordier ow the Temperature of 



\y into the solid state ; or if it is decomposed, so as to furnish 

 solid parts and gaseous parts. There is nothing improbable in 

 the latter idea ; in fact, the consolidation of lavas daily presents 

 a very striking example of the production of gas by refrigera- 

 tion. If we admit this supposition, we can account for the ori- 

 gin of the first matter of earthquakes in a very natural manner. 

 An excessive temperature keeps this first matter in the gaseous 

 state, notwithstanding the enormous pressure which it experien- 

 ces at these great depths. The capricious nature of the pheno- 

 mena of earthquakes would also be accounted for by the ex- 

 treme inequality of the internal surface of the crust of the 

 earth. 



20. The preceding data lead to an entirely new explanation 

 of volcanic phenomena ; an explanation which will perhaps ap- 

 pear more satisfactory, at least to the very small number of per- 

 sons who have a just and complete idea of the elements of the 

 question, than any that has hitherto been proposed. These 

 phenomena appear to us a simple and natural result of the in- 

 ternal refrigeration of the globe, a purely thermometrical effect. 

 The internal fluid mass is submitted to an increasing pressure, 

 which is occasioned by two forces whose power is immense, al- 

 though their effects may be slow and not very perceptible. On 

 the one hand, the solid crust contracts more and more in pro- 

 portion as its temperature diminishes, and this contraction is ne- 

 cessarily greater than that which the central mass experiences in 

 the same time ; on the other hand, this same envelope, in con- 

 sequence of the insensible acceleration of the rotatory motion, 

 loses its internal capacity in proportion as it recedes more from 

 the spherical form. The internal fluid matters are forced out- 

 wards, under the form of lavas, by those habitual vents which 

 are named volcanoes, and with the circumstances which the pre- 

 vious accumulation of gaseous matters, which are naturally pro- 

 duced in the interior, give to eruptions. This hypothesis needs 

 not excite astonishment, for I can demonstrate its probability by 

 a very simple calculation. 



In 1803 I cubed in TenerifFe, as nearly as it was possible, 

 the matters ejected by the eruptions of 1705 and 1798. I per- 

 formed the same operation with regard to the products of two 

 eruptions still more perfectly isolated, which exist in the extinct 



