210 Sir A. Crichton on the [March, 



analogy between the igneous phenomena of Duida and volca- 

 nos, but merely to justify the assertion concerning the deep 

 fissures of granitic peaks, and the heat derived from their foun- 

 dations : where it may be supposed there is a vicinity to the 

 still hot nucleus of the earth. 



The softening, elevation, and rupture, of the first formed gra- 

 nitic mountains, and the action of the agitated ocean, would pro- 

 duce the separation of an infinite number of minute grains of 

 the nevvly-fcu-med crystalline substances, many of which would 

 be suspended mechanically for a longer or shorter time accord- 

 ing to their respective gravity on the one hand, and the greater 

 or lesser agitation of the waters on the other. 



Some earthy oxides, such as the argillaceous oxide or clay, 

 which have a kind of mechanical attraction for water, which is 

 not perfectly understood, would be longer suspended than the 

 minute crystals of mica, amphibole, quartz, or feldspar, and 

 would be precipitated, all other things being alike, at a later 

 period, and hence in the generality of cases gneiss hes under 

 the argillaceous beds and rocks where these are found. 



The presence of anthracite in the fissures of pripiitive rocks 

 demonstrates that carbon was an elementary ingredient in the 

 nucleus of the elementary globe ; and it is therefore reasonable 

 to conclude that, during the state of ignition, it would attract 

 oxygen from the decomposition of the water, and form carbonic 

 acid, which, after combining with the waters, would render it a 

 solvent for all such metallic oxides as have a powerful attraction 

 for it, and which are rendered more soluble through its agency, 

 such as lime (oxide of calcium), and magnesia (oxide of magne- 

 sium). 



The precipitation of such carbonated oxides (limestone and 

 magnesian rocks) would dejend chiefly on the agency of three 

 well known causes ; Jirst, the continued formation of more 

 oxides than the waters could dissolve ; secondly, the diminution 

 of temperature ; and tinrdlij, the effects of evaporation. 



These few principles throw much light on the formation of 

 jaspers and serpentines of aqueous origin, and of the limestone 

 rocks, esjiecially if (o such causes be added the heat of the sub- 

 jacent rock on which they fell, and the pressure of the strata 

 which were precipitated after them : and the same principles 

 lead to an explanation of the various anomalies we meet with in 

 the forms and relative positions of the primitive rocks. 



All the formations from the granite to the deposits on which 

 the diluvian boulder stones and gravel lie, demonstrate, by their 

 organic remains, that there has been a gradual diminution of 

 temperature from the earliest times till the earth was fitted for 

 the creation of rnan, and the present race of animals, at which 

 period it appears to have been entirely under solar influence and 

 seasons. 



