60 



ever the size, and whatever the amount of Rise, are founded chiefly 

 on the following circumstances: 1. The height of sedimentary beds 

 and marine bodies, whether corresponding or not to those of ad- 

 jacent seas, or of the actual globe. 2. The height of terraces re- 

 sembling sea beaches. 3. The height of ripple marks. 4. The 

 change of posture which horizontal strata undergo in the neigh- 

 bourhood of " unstratified rocks." 5. The various heights at which 

 the same rocks occur in different parts of their course. 6. The an- 

 ticlinical posture of strata frequent in, though not confined to, 

 mountain chains. 7. The arched or domed configuration of some 

 strata. 8. The occurrence of coral, apparently recent, high above 

 the present surface of the sea. 9. The position of ancient buildings, 

 viz. the temple of Serapis at Puzzoli, &c. I have not time to con- 

 sider these arguments in detail; each deserves to form the subject 

 of a separate treatise. Some of them prove not Elevation, but only 

 change of level, which Subsidence would explain equally well. Some 

 prove local disturbance, whereby one portion may have been thrown 

 up, the other down. Some again aftbrd a fair presumption of real 

 local Elevation or Ascent. Most of them are good to a certain point : 

 all are continually overstrained; and I am frequently astonished to 

 observe how prodigious the weight, how slender the sti'ing that 

 supports it. 



The assigned Causes of Elevation are exceedingly various. One 

 author raises the bottom of the sea by earthquakes ; another, by sub- 

 terranean fire ; another, by aqueous vapour ; another, by the contact 

 of water with the metallic bases of the earth and alkalis. Heim 

 ascribes it to gas ; Playfair, to expansive force acting from beneath ; 

 Necker de Saussure connects it with magnetism ; Wrede, with a slow 

 continuous change in the position of the axis <ii the earth ; Leslie 

 figured to himself a stratum of concentrated atmospheric air under 

 the ocean, to be applied, I suppose, to the same purpose. 



It is impossible within the narrow limits of this discourse, that I 

 can enter into the merits of these and other hypotheses seriatim. I 

 must therefore throw them into two classes, the first of explosive 

 forces, the second of sustaining forces; they are one and the same in 

 Plutonic language, but still it will be convenient to separate them. 



That explosive forces exist, or may exist, under the surface, no one 

 can denv; but I cannot adopt the opinion (however high the autho- 

 rity from which it comes,) that " in volcanic eruptions v/e find a power 

 " competent to raise Continents out of the ocean." The force we find in 

 volcanic eruptions is limited in time, place and action ; it fuses bodies 

 of easy fusibility ; it tosses up those that are refractory, and thus 

 forms either a current of lava or a shower of stones, scoriae and ashes. 

 What resemblance is there between this operation and the rise of a 

 continent r With more propriety might it have been said that in a mole- 

 hill we behold the action of a cause competent to raise mountains. 



If by Continent is meant a whole Continent, and nothing but a 

 Continent, its rise, provided this happened only once, would seem 

 difficult to understand ; but to me still more incomprehensible is 

 the confident assurance we continually receive from writers of high 



