144 



GEOLOGY OF THE LOTHIANS. 



tificially fused mass of lava. " Besides all other properties/ 4 

 he remarks, " it possesses the fusibility of the glasses, since 

 it softens completely at 18, that is 14 or 15 degrees below 

 the softening point of any of the stony lavas. Being ex- 

 posed to the process of regulated cooling, it gave the same 

 result as all the other lava glasses. In the lower points it 

 yielded a liver crystallite infusible under 30, and in the 

 higher a stony substance like a common lava or whin, 

 and fusible only at 35." 



We here extract from Sir James HalFs paper the Table of 

 the fusibilities of the traps and lavas which he examined, 

 and from it " it may be observed that the original whins 

 soften in a range from 38 to 55, the glasses from 15 to 24, 

 and the artificial crystallite from 32 to 45.'" 



Substances. 



Original 

 softened. 



Glass 

 softened. 



Crystallite 

 softened. 



Whin (Greenstone) of Bell's Mills 

 Quarry, 



Whin (Basaltic Clinkstone) of 

 Castle Rock, 



Whin of basaltic column, Arthur's 

 Seat, .... 



Whin (Basalt) near Duddingston 

 Loch, .... 



Whin (Greenstone) of Salisbury 

 Crags, .... 



Whin (Syenitic Greenstone) Wa- 

 ter of Leith, . 



Whin (Basalt) of Staffa, 



Lava of Catania, . 



Lava of Sta. Venere, Piedmont, 



Lava of La Motta, 



Lava ? of Iceland, 



Lava of Torre del Grecco, 



Lava of Vesuvius, 1785, 



) 



\ 

 \ 



\ 



40 

 45 

 55 

 53 

 55 



35 



38 

 33 

 32 

 36 

 35 

 40 



18 



15 

 22 

 18 

 24 

 24 



16 



144 



18 



18 



18 



15 



18 



18 



32 



35 



35 



38 



38 



37 

 35 

 38 

 36 

 36 

 45 

 28 

 35 



The other discoveries of Sir James Hall we need not here 

 notice in detail. His experiments on limestone and coal are 



