On Metallic Minerals. 405 



resist the Meather equally well, or vice veisa, as there 

 is a great difference iu the modus operandi of these different 

 causes. Much depends upon the nature, particularly 

 as regards the structure of the stones, for instance 

 compact stones usually resist tlie weather well, but will fly 

 immediately in the fire as flint, quartz rock, &c. On the 

 contrary, rocks and stones of agranular and slaty structure 

 Mill often crumble away in the air, but which would 

 resist heat remarkably well. But it is ridiculous to 

 dwell upon so obvious a truth, which would not have been 

 done if an opinion were not prevalent that any stone which 

 will endure heat, will also endure what is so very different 

 the capricious changes of the atmosphere at all times,— the 

 combined action of heat and moisture, in the summer, and 

 the still more powerful combination of cold and moisture 

 in the winter. 



In corroboration of what I Iiave been saying, the sand- 

 stone in question is by no means extraordinary as a building 

 stone, but for the particular purposes of constructing the 

 furnaces and hearths stone, it is not easy to conceive a 

 better material. Upon exannning the sandstone with a 

 microscope, it appears to be composed of grey grains of 

 quartz, and a soniewhat powdery mineral of a white colour 

 which ajjpcars to be dccoujposed felspar. All parts of it 

 are infu>ib!e under the blow-pipe. 



Above this sandstone lies in conformable, that is parallel 

 order, and close contact, a dark grey wacke, averaging 

 twelve feet in thickness, immediately above which rises 

 at an angle of about 45« to the height of nearly one hundred' 

 feet, a mass of sandy alluvium. There is not the least 

 doubt that the limolone before mentioned overlies tlie grey 

 wacke; but whither other intervening strata ma) not occur 

 ii a qiK'Hlion 1 cantiut decide. 



