304 Horner's Geological Address. 



mass of solid pure malachite was found, of a bulk estimated 

 at upwards of half a million of pounds weight, presenting in 

 its interior the wavy radiations and silky structure of that 

 beautiful mineral ; almost identical in structure with many 

 calcareous semi-crystalline minerals, of whose aqueous origin 

 no doubt exists. 



All the best iron of Russia is brought from the Ural chain 

 and its flanks. It is found in veins in greenstones, and in- 

 termixed with the mass of erupted rocks of that class, often 

 in great abundance at the junction of the igneous and strati- 

 fied rocks, these last being in a metamorphic state. Mag- 

 netic iron ore is the chief form in which the metal is found, 

 and it constitutes vast masses, sometimes^worked in an open 

 quarry. 



Changes in the Relative Level of Sea and Land. 



You are well aware that proofs of changes in the relative 

 level of the sea and land along certain shores, particularly 

 in the Baltic and Mediterranean, since our continents and 

 adjacent islands were bounded by their present lines of coast, 

 had attracted the attention of some of the earlier geologists ; 

 but it is only within a comparatively recent period that the 

 discovery, in numerous instances, of the action of the sea at 

 elevations far above its present level, in what have been 

 termed raised beaches, has excited due attention to this most 

 important class of geological phenomena ; changes which 

 may almost be said to come within the range of our expe- 

 rience, and which appear to afford a key to the right solution 

 of many analogous changes during periods long antecedent. 

 We have for some time known that eroded rocks, and long 

 lines of level beds or terraces of shingle, sand and clay, 

 mixed with broken shells like what we now find at the sea- 

 shore, are met with along the coasts of Sweden, and in Nor- 

 way and the islands adjacent, from the Naze to the North 

 Cape, and even to Spitzbergen. These beds of detritus, 

 which have been found at elevations of 600 feet, and are 

 sometimes above 160 feet in thickness, usually rest on the 

 solid rock, and frequently contain shells in a perfect state of 



