182 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 31, 



and here and there we observe small aggregations, evidently arising 

 from foreign matters present in the original soapstone, which have 

 separated themselves. 



In repeating this experiment with a view to the economical use of 

 soapstone for the bottom of furnaces, I found that the metal had 

 broken through the protecting lining (which in this case was not so 

 thick), and had gone right through the substance of the soapstone 

 blocks, which had acted as a filter. The blocks themselves retained 

 their form completely, and were perfect at the joints ; but below 

 them was found a large mass of metal which had percolated through 

 them ; and the blocks themselves were converted into heavy semi- 

 metallic masses, much resembling in appearance the magnesian rocks 

 impregnated with metallic ores found in the veins of this district. It 

 was also easy to see that an arranging force had likewise come into 

 play, as the sulphurets of the various metals previously existing in 

 the matte as a homogeneous compound, were here separated and 

 showed themselves distinctly crystalline. 



Many other experiments of a similar character were made ; but, 

 as they were principally connected with the formation of minerals, 

 they are not so immediately related to this subject. 



The above facts are, however, I think, sufficiently conclusive to 

 show that we may have an altered chemical, as well as molecular, 

 arrangement at temperatures below that at which softening is pro- 

 duced. 



That we may, however, sometimes have an arrangement analogous 

 to foliated structure in rocks generally considered as of igneous 

 origin, and which have been fluid, must be admitted. The structure 

 of graphic granite illustrates this well ; and Sedgwick mentions that 

 the granite of St. Austell in Cornwall has a grain. Keilhau men- 

 tions*, that in a granitic rock at a place called Salmelic, in Norway, 

 he found a parallel structure, sufficiently distinct to determine a strike 

 and dip, induced by the presence of crystals of flesh-coloured ortho- 

 klase. 



This arrangement cannot, however, I think, have anything in 

 common with that found sometimes in volcanic rocks, and which is 

 often seen in slags and glass, produced artificially, and which seem 

 probably due to similar causes as those producing the ribboned 

 structure of glacial ice. In the specimen of glass here produced we 

 have an arrangement evidently due to this cause and to a subsequent 

 crystallization superadded, in which the crystalline arrangement has 

 followed the strise of the glass, previously invisible. Some rocks 

 certainly igneous may have been formed in a similar manner ; but 

 here, in the case of the glass, we do not have the chemical action as in 

 the production of foliated rocks ; since the glass is only to be regarded 

 as a homogeneous body, modified by crystalline forces, according to 

 pre-existing lines. 



It will be found that many minerals apparently possess in them- 

 selves a certain independent arranging power. Minerals do not only 



* Noiske Mag. f. Natuiv. vol. ii. p. 372. 



