1867.] Louis Figuier. 169 



that probably there is an ether, and those, of the eminent spectro- 

 scopic observers of the nebulae, Huggins and Miller, which point 

 to the existence of still unformed systems, his readers would 

 have had sound scientific facts to guide them, and would have 

 been able to compare them with the well-established data of 

 astronomers. 



As the matter stands at present, the arguments of M. Figuier 

 or his translator are based to a large extent on hypotheses, which 

 operate like a double-edged sword. 



For example, the central heat of the earth inferred from the 

 existence of volcanoes and hot springs* in so many parts of the 

 globe, and from the increase in the temperature of 1° Fht. for 

 every 60 feet descent, is a very plausible argument in favour of 

 the original state of igneous fusion, of which these phenomena 

 seem to be but traces, but it is no proof. Although this 

 increase in temperature as we descend is stoutly denied by some, 

 yet it seems to be generally admitted; but the question still 

 remains, could this state of fluidity exist at the centre consonant 

 with the undoubted immense pressure of the circumference ? Sir 

 Charles Lyell* says : — " This theory seems wholly inconsistent 

 with the laws which regulate the circulation of heat through fluid 

 bodies; for if the central heat were as intense as is represented, 

 there must be a circulation of currents tending to equalize the 

 temperature of the resulting fluids, and the solid crust itself would 

 be melted. Instead of an original central heat, we may, perhaps, 

 refer the heat of the interior to chemical changes constantly going 

 on in the earth's crust ; for the general effects of chemical combina- 

 tion is the evolution of heat and electricity, which, in their turn, 

 become sources of new chemical changes." 



When Sir Humphry Davy succeeded in isolating the metals 

 potassium and sodium, it was supposed that immense quantities 

 of unoxidized metals might exist at great depths ; and when water 

 percolating through the rocks gained access to these masses, 

 oxidation of the metals took place with the evolution of intense 

 heat sufficient to melt neighbouring rocks, the hydrogen of the 

 water would escape in the direction of least resistance, carrying 

 with it molten lava, and producing the ordinary volcanic pheno- 

 mena. Dr. Daubeny also supports this view, and there can be no 

 doubt that chemical operation going on in the interior of the earth 

 is sufficient to produce volcanic action of any degree of intensity. 



With regard to the origin of life on our globe, M. Figuier does 

 not dogmatize : — " Did plants precede animals, we cannot tell, but 

 such would appear to have been the order of creation." Our globe, 

 he thinks, during the Cambrian and Silurian periods was not yet 

 mature enough for the existence of the higher organisms. " A 

 * ' Principles/ 9th edition, p. 545. 



