
522 PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 
1 +3 grammes yielded— 

Silica, 5 , °658 
From Alumina, . OTA 
* 669 = 51° 461 
Alumina, . ‘ ° - 2:°968 
Ferric Oxide, . . s 2°45) 
Ferrous Oxide, . ‘ , 9 o61 
Manganous Oxide, , » iL 076 
Lime, ° 5 $ med073 
Magnesia, . : § ») 20=461 
Potash, . : \ § * 683 
Soda, : : : Jt .10'305 
Water, . ; . . *683 
100 * 822 
Probable impurity, a trace of the felspar. 
From Igneous Rocks. 
17. In speaking under Augite of its vitreous allomorph, which is to be found 
at Elie, Kinkell, &c., the associated occurrence of glossy black hornblende at 
both of these localities was noticed. This hornblende is found at Elie, rarely 
in the tuff, and more commonly in the injected dykes which cut it, to the east 
of the town. 
The appearances which it presents are well marked and peculiar. It 
occurs in cleavable masses of the size of beans to that of small eggs; the 
cleavages give the angle 124° 19’. The colour is black, with a shade of green; 
it is highly lustrous. 
It is not easy to form an opinion as to whether these masses are imbedded, 
worn fragments; or crystalline infiltrations filling pre-existent cavities which 
had a rounded outline. 
The argument for the former view is that crystals of sanidine, which might 
be held to be water or sand worn, are found imbedded in the same rock, at no 
great distance. An argument which points in the opposite direction is, that 
the cleavages of a newly detached mass invariably pass over its whole surface 
uninterruptedly, abutting against the containing rock, without exhibiting, near 
the surfaces of the fragment, any internal fractures, bruise, or perceptible 
paling of the colour; all of which we should expect to find in a rolled and 
fractured fragment. 
On the whole, the appearances are most favourable to formation in situ; 
though it must be admitted that the single broad cleavage is altogether anoma- 

