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



expected that the faults would have been obliterated, or that both 

 sides would have been equally affected. 



At the hmestone quarry on the road to Crianlorich, previously de- 

 scribed, p. 166, where the limestone is foliated, we have the foliation 

 affected by faults and curved, and in one place a portion enclosed 

 between two faults had the foliation curved on both sides in a nearly 

 circular direction ; so that there is here also reason to believe that 

 the foliation took place subsequently to the faults, which otherwise 

 would not have retained the sharp and defined angles here seen. 



In submitting this opinion as to the temperature at which foliation 

 took place, it can be objected, however, with reason, that in the present 

 state of chemical science we have no right to assume that such che- 

 mical action and arrangement can take place in solid bodies without 

 external change of form. Chemists will no doubt admit that in 

 homogeneous bodies of one composition we may have a complete 

 change of molecular arrangement without any change of form ; — thus, 

 that a mass of bar-iron from being fibrous may become crystal- 

 line — 

 that sugar-candy may from an amorphous state become crystal- 

 line — 

 that large crystals of sulphur may change their structure, be- 

 coming an aggregate of small crystals belonging to a different 

 crystalline system — 

 that the sandstone bed of a blast furnace or the bricks of 

 kiln-walls may by the action of heat acquire a columnar or 

 basaltic structure. 

 But in all these cases we have no chemical action, no production of 

 other and totally distinct compounds as in foliated rocks, — we have 

 only the results of a molecular arranging force * . It is necessary, 

 therefore, before the view I have brought forward, with reference to 

 the production of foliated rocks at comparatively low temperatures, 

 can be securely established, that we have some data to prove that 

 such action and changes can really take place. I endeavoured, 

 therefore, to procure experimental proof of this with direct reference 

 to the rocks, but met with many difficulties. 



Thus, I often could not succeed in regulating the heat to sustain 

 such temperatures as seemed necessary, and found that, the instant a 

 pasty or semifluid state was induced, I could not obtain satisfactory 

 results. The action of the air in oxidizing the iron present as prot- 

 oxide to the state of peroxide also introduced a new element which 

 would have been gladly dispensed with. 



On taking, however, a rock like steatite, which we have in Norway 

 in such quantities as to use it as a building-material, — and which is at 

 once one of the most infusible of rocks, and nearly altogether free 

 from iron, — I was not annoyed by the above difficulties, but found 

 another obstacle in the way. 



The results, however, on prolonged treatment of this rock, were 

 so satisfactory as to be very encouraging as a beginning, and I found 

 that a slightly foliated structure was evidently being induced. The 



* See also Hausmann on Arsenikglas, &c., Quart. Journ. Geol. Soc. vol. vii. 

 part 2, page 2. 



