169 



Transformation of lias into saccharoid limestone seen in the Py- 

 renees. I tliink it unnecessary to detail to you the descriptions 

 which Mr. Murchison has given of the Change of structure, or 

 even of substance that take place at the Malvern Hills and at sundry 

 other places in Wales, and on the confines of Wales frequently, 

 though not always, in the vicinity of trap and sienite, because they 

 are in general the same as have been observed repeatedly in other 

 districts. The phsenoraena at Old Radnor the author remarks are 

 very analogous to those of the Val di Fassa in the Tyrol. It may, 

 however, be proper to mention, not as a novelty, but as a circum- 

 stance the frequent occurrence of which is little attended to, that in 

 Carmarthenshire the line of altered rock produced by the proximity, 

 or as it is called the protrusion of a mass of porphyritic trap, is pa- 

 rallel to the strike of the grauwacke so altered. At Caer Caradoc, 

 the Wrekin, the Stiperstones, and elsewhere, a stratified sandstone 

 is at its junction with trap, converted into quartz rock. One other 

 circumstance deserves to be noticed; the range of the Stiperstones, 

 along which these Plutonic appearances present themselves, is 

 flanked on either side by metalliferous deposits, but not of the same 

 kind, the copper ores being all found on one side of the range, the 

 lead ores on the other. An analogous case will be seen in Hum- 

 boldt's account of the country situate between the Oural and Altaic 

 chains. A fault or fissure is there traceable through not less than 

 16° of longitude, forming a crest or water-shed; the rocks are nearly 

 the same as those of Shropshire ; they comprehend a granite (uncon- 

 nected with gneiss,) clay-slate, grauwacke-slate, augitic porphyry, 

 and transition limestone, once compact but now granular. Ma- 

 lachite and red Copper ore are found on one side of the ridge, argen- 

 tiferous galena on both. 



Such are the Plutonic phaenomena, for an explanation of which 

 we rely chiefly on the assistance of chemistry; but there is another 

 train of phaenomena which renders a close and intimate alliance be- 

 tween this science and our own, no less desirable. The spontaneous 

 generation, shall I call it ? of agate, of chert, of hornstone, of flint, in 

 the midst of sedimentary calcareous deposits, apparently through 

 the instrumentality of animal or vegetable matter, in which little or 

 no silex is to be met with, is one of those mysterious operations of 

 nature which can nowhere be satisfactorily accounted for unless 

 in the laboratory. The coralline agates of Antigua, the entrochal 

 cherts of Derbyshire, the siliceous shells ofBlackdown or Fontaine- 

 bleau, the chalcedonic alcyonia of Pewsey, pieces of fossil wood 

 either imbedded in strata or loosely scattered over sandy deserts, 

 the flinty casts of echini and other substances in the midst of our 

 chalk, all these suggest a course of experimental investigation which 

 we are entitled to hope, if undertaken in earnest, would not be un- 

 dertaken in vain. 



Gentlemen, I have great satisfaction in announcing to you, that 

 at the opening of the present Session of the Royal Society, one of 

 the Royal Medals was awarded to our Foreign Secretary as the au- 



