532 PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 
27. From the great bed of serpentine at Portsoy. 
In speaking of the change of augite into serpentine at this spot, it was 
mentioned that the augitic pseudomorphs which were analysed lay imbedded 
in what appears to be a hydrated asbestus. This substance is to be here seen 
of different appearances, which are all more or less perfected passages into 
serpentine. 
The mineral bears in general some resemblance to a soft nephrite. It is 
of a pale green colour, occasionally of a matted fibrous structure, and of great 
toughness ; its specific gravity is 2° 388. 
Three specimens, illustrating the progressive steps of the conversion, were 
selected ; the two first were only partially,—that in which the change seemed 
perfected was completely examined. The first was tough, close in structure, 
and harder than the others, being altogether less serpentinous-looking. 

First. Second. Third. 
On 1° grm. On 1°2 grm. On 1 °3 grm. 
Silica, r e : & 46-716 46 -923 
Alumina, . 5 ‘ ae * 625 * 633 
Ferric Oxide, . é oe * 007 - 007 
Ferrous Oxide, . ' a5 bei 1° 674 
Manganous Oxide, . ae ffi 769 
Lime, : ; : Ss not det. 9: 907 
Magnesia, . . : =i 25 + 758 25 + 846 
Potash, : : ae oT ah “DOr 
Soda, : é eo Ray oo - 582 
Water, : Wivigerd ie 12°84 
99-748 
Insoluble Silica, . 5 ae 2°32 2295 per cent. 
Loss in bath, . ot oh ses 3°2 3°2 if 
In this case the alkalies are retained during the change. 
Though I have said that the above substance appears to be a hydrated | 
asbestus, it is by no means improbable that it represents what was originally | 
the felspathic portion of the rock. As a general rule, the fibrous structure is | 
obscure, and two questions in this connection call for answer. . 
The first,—if the transmuted rock was primarily a gabbro, what now repre- | 
sents the felspar? 
The second,—if this pale green mineral was originally asbestus, then the 
rock must have consisted of a great mass of matted asbestus, holding augitic 
crystals in their meshes, and of little else. Such a compound is unknown. 
Now, one subsidiary bed of the serpentine here—that of which the portions 
we are considering are merely extremely well characterised illustrations—con- 
sists solely of the previously described red pseudomorphs of augite, set in or 

