326 



EECEEATIVE SCIENCE. 



veins, but these traps and dykes can be 

 traced downwards to the igneous series, and 

 be proved to have been ejected through and 

 over the sedimentary matter they have dis- 

 turbed, after that sedimentary matter had 

 been accumulated in the beds of seas and 

 lakes, and hardened into rock. Familiar as 

 this fact is to every student of geology, in- 

 deed, without a recognition of the chrono- 

 logical order of the strata of the earth's 

 crust, there is no science in G-eology at all, 

 yet it needs here to be enforced as the leading 

 link in the chain of evidence by which the 

 theory of the internal heat of the earth is to 



Order of Strata, forming the lower portion of the 

 earth's crust. — 1 , Plutonic focks ; 2, gneiss ; 3, mica- 

 schist ; 4, clay-slate ; 5, Silurian ; 6, old red sand- 

 stone. 



be established. It matters not under what 

 form the igneous rocks present themselves, 

 whether as granite, porphyry, basalt, chlorite, 

 or serpentine, they aU agree in their general 

 characteristics as the crystalline products of 

 simple fusion, and when we arrive in our 

 upward course upon the gneiss and mica- 

 schist, we find stratification by the agency of 

 Water, and crystallization through the de- 

 posit having been made upon the heated 

 granite bed. Thus the lowest of the series 

 of rocks forming the earth's crust, as far as 



we are acquainted with them, were originally 

 in a state of fluidity by heat, and, in cooling, 

 the constituent materials assumed either the 

 crystalline confusion observable in granite, 

 or the columnar form seen in basalt, and 

 sometimes in porphyry. These lowest beds 

 also rise to the highest altitudes upon the 

 earth's surface ; the granite of the Alps only 

 dips under the tertiary of Vienna, to rise 

 again on the western end of the Carpathians, 

 the eastern half of which consists of secondary, 

 greatly modified by the heat of the granite, 

 on the shoulders of which it was originally 

 heaved to the surface. The peaks of the 

 Caucasus, the Grampians, the hills of 

 Auvergne, the Pyrenees, the north of Wales, 

 and the south of Ireland, and the belt of 

 country from the Ural chain to the western 

 coast of Scandinavia, claim kindred as to their 

 origin with the tuff and pumice of Sicily and 

 Naples, Auvergne and Dresden. Unless the 

 heat had been sufficient to upheave and break 

 through the first-formed crust of igneous 

 matter, and to have continued even till now 

 to disturb the uppermost layers of water- 

 formed rock, the earth must have remained 

 a sightless and unfruitful level plain — a plain 

 submerged, perhaps, under a thin, continuous 

 fibn of water. But the struggle of the heat 

 for escape has caused the protrusion of traps 

 that have scorched the rocks through w^hich 

 they passed on their way to the cool surface. 

 It has converted beds of coal into anthracite, 

 brought within man's reach veins of useful 

 metals, beds of useful coal, and, in many 

 places, exposed to view for his instruction 

 the order of superposition, and the relative 

 places in time of the several sedimentary for- 

 mations. To the earthquake and the volcanic 

 throe he is indebted for the sparkling stream 

 that is fed for ever from the mountain snows, 

 indebted for the rounded hills that feed his 

 flocks, and the table-lands that wave with corn, 

 and for the fertile valleys wherein the soaring 

 bird and the soaring heart sing together to 

 the praise of God. If we leave Europe, and 



