I6 THE WORLD. 



glomerate. Occasionally nails, or other pieces of iron, are found 

 in the centre of a hard nodule of sandstone, formed by this pro- 

 cess. The engraving, from Dr. Mantell's " Wonders of Geolo- 

 gy," is a very" interesting- specimen, it is a conglomerate of glass 

 beads, knives, and sand, cemented together by an infiltration of 

 iron, derived from the oxidation of the blades. It contains two 

 silver pennies of Edward I, and was dug up at a depth of ten 

 feet in the river Dove in Derbyshire. The coins are presumed 

 to have been a part of the treasures contained in the military chest 

 of the Earl of Lancaster, which was lost in crossing the river in 

 the dark ; more than five centuries must therefore have elapsed 

 since its submersion. The ore called bog-iron, is formed by the 

 infiltration of water impregnated with iron, and various kinds of 

 wood are colored black by the same cause. Iron, it is well known 

 is one of the chief ingredients in many celebrated mineral wa- 

 ters, frequently in the shape of a carbonate. The consolidation 

 of sand and other loose materials by the agency of mineral wa- 

 ters, is everywhere going on, and in much greater extent than 

 can be easily comprehended ; small and apparently simple as are 

 the means employed, yet the effects are magnificent. 



The detritus borne down by the mountain streams falls at last, 

 quietly into the ocean, or is deposited upon the rich soil of some 

 delta, after a certain time the mass is cemented together by other 

 mineral ingredients dissolved in the water, and beds of compact 

 stone, in which are entombed the remains of animate and inani- 

 mate existence, are formed slowly but surely, for ihe use of most 

 distant generations. The twigs and leaves, and insects, which 

 fall into the petrifying springs are incrusted with a coating of 

 stone, or are slowly transmuted into mineral substance for the 

 inspection and admiration of a future race. Thus the change 

 continually goes on. The frost, the storm, and the stream, and 

 in many volcanic districts the carbonic acid, continually given off, 

 as for example, in the neighborhood of the extinct volcanoes of 

 Auvergne in France, cause even the granite rocks to crumble 

 and fall away; but in a thousand other places the process of re- 

 union is going on, and different kinds of stone are being formed 

 from the ruins of the old. Besides the springs to which we have 



