298 ■ Notices respectifig New Books. 



other. Whenever beds of sedimentary origin possess an anticlinal 

 or quaquaversal dip, at a higher angle than water could have depo- 

 sited them, they may be said, in a general sense, to form a " crater 

 of elevation." This crater may be either circular or elliptical ; or 

 the ellipse may be so long as to appear linear ; it may arise from the 

 direct outbreak of a volcano, or from those other causes of elevation 

 which probably exist ; it may have a symmetrical cavity in its cen- 

 tre, or it may be filled up by the elevated matter, and have no cavity 

 at all; — yet the mechanical elements of an elevation-crater remain 

 unaltered. We have plenty of such craters in our own land ; the 

 Weald of Kent (allowing for subsequent denudation) is an elevation - 

 crater ; so are the more symmetrical domes of limestone near Dud- 

 ley (one of which has a crateriform depression on its summit) ; and 

 so are the beautiful valleys of Woolhope in Herefordshire and of 

 Ashover near Matlock. Wherever the inclined beds are of aqueous 

 deposition (whether their ingredients are volcanic or not is immate- 

 rial), there is no difficulty in attributing their present arrangement 

 to elevatory forces. But when a crateriform cavity is surrounded by 

 inclined masses of lava, scoriae, or other purely igneous matter, the 

 problem is far more difficult, and becomes a fair question for contro- 

 versy. Whether the materials which form a volcanic cone are ele- 

 vated or erupted, they equally assume a quaquaversal inclination, 

 and it is often impossible to determine whether they have originally 

 formed a continuous stratum or have been outpoured at successive 

 epochs. Nor does the difficulty appear to us to be diminished by 

 the presence in a crater of a trachytic nucleus, which Dr. Daubeny 

 considers to be conclusive evidence of elevation ; for if the trachyte 

 has once been fluid, why may it not have been ejected up the funnel 

 of the volcano in a semi-liquid form ? In some countries, Asia Mi- 

 nor for instance, there are regular coulees of trachyte which have 

 flowed down the existing valleys, and we do not therefore see why 

 trachyte in a less perfect state of fluidity may not have blocked up 

 the mouths of volcanos, or even, when in an almost solid state, have 

 formed conical masses, like the Puy de Dome, on the surface of the 

 earth. 



It is nevertheless highly probal)le that nearly every volcanic cone 

 has a nucleus of elevated rocks. Before a volcano can commence at 

 a new point a vent must be made for it, either by pushing the in- 

 cumbent strata laterally, or, which is far easier, by bursting them 

 upwards. But in the majority of cases these rocks so elevated 

 would soon be buried far from human ken by the accumulations of 

 erupted matter. 



The author next treats of the subject of basaltic or trap rocks, 

 which he considers to be caused by volcanic eruptions taking place 

 under submarine pressure, instead of exploding into the atmosphere 

 like ordinary volcanos. It was hardly necessary at this time of day 

 to go into much detail to prove the connection between trap and 

 volcanic rocks ; we should rather go a step further, and assert the 

 actual identity of the operations which produce them. It appears 

 to us X^Sit pressure of any kind is sufficient to account for the dif- 



