274 M. L. Cordier, on the Temperature of 



may receive from the solar rays. The latter opinion at length 

 became the prevailing one. It owed its success in a great mea- 

 sure to the influence of the celebrated geological system pro- 

 duced about the middle of the last century, of which Pallas, 

 Saussure and Werner were the principal promoters, and which 

 for a long time met with no opposition. This system supposes 

 that the original fluidity of the globe took place through the 

 medium of water, that the whole mass was consolidated, stratum 

 after stratum, from the centre to the circumference, by aqueous 

 crystallization ; and that the volcanic phenomena are mere local 

 effects. 



The opinion on this subject has undergone a great change 

 within these few years. This change, which has been extremely 

 slow in its progress, so great were existing prejudices, commen- 

 ced at the end of the last century. It is to be chiefly attributed 

 to the following circumstances : Important discoveries have been 

 made in geology ; the relative position of the materials compos- 

 ing the oldest formations of the crust of the globe, has been found 

 to be different from what had been formerly asserted ; it has 

 been proved that the volcanic agents reside under the primitive 

 rocks ; the true nature of lavas, and their identity in all parts of 

 the earth, have been discovered ; the analogy of a multitude of 

 strata of all ages to lavas has been demonstrated ; the facility 

 with which all these originally fluid and incandescent matters 

 have crystallized by mere cooling, has been proved and under- 

 stood ; and the theory of aqueous crystallizations has become 

 perplexed. On the other hand, accurate and numerous facts 

 relating to the motion of radiant heat, and of the heat which is 

 propagated in bodies from one molecule to another, have been 

 made known by satisfactory experiments. These facts have been 

 connected by mathematical theories of the most general nature. 

 Ingenious observations have placed beyond doubt the continual 

 radiation of the superficial heac of the earth into celestial space. 

 The ideas which have been long entertained in regard to the 

 inconsiderable depths to which the horary, daily, monthly and 

 annual variations of temperature reach in the soil or strata of 

 diff*erent countries, and the level at which a fixed temperature 

 commences, have been carefully verified. Lastly, new experi-. 

 ments have been undertaken regarding the temperature of deep 

 places accessible to us, and that of the waters coming from them. 



