Dr Hlbbert on the Distrihuticyn 
a bed of porcelain earth is produced. This occurs on the estate 
of Arthur Nicholson, Esq. and may probably be an object of 
commercial notice. 
Distribution of the Serpentine^ Dlallage cmd Strata of Unst, 
In the adjoining island of Unst, to the north of Fetlar, is 
another central mass of serpentine, in almost every respect like 
that of the central mass of Fetlar. This rock may be traced 
from the west of Gallowhill^ near Belmont, bending in a north- 
easterly direction to the line of coast between Norwich Bay and 
the north of Balta Island. It is about ten miles in length, 
while its breadth gradually increases from one to three miles^ 
This mass of serpentine is particularly distinguished by the 
very abundant occurrence in it of the chromate of iron, chiefly 
observable in the neighbourhood of Balta Sound. I was first 
led to a search after tliis ore, by observing innumerable frag- 
ments of it strewed about the hill, and even employed for the 
purpose of fortifying the fences of the country. It is observed, 
first, in the form of imbedded masses, as at Buness, close to the 
house of the proprietor, Thomas Edmonstone, Esq, The ex- 
tent of the greatest mass is not, however, apparent, as it is on 
one side concealed by the sea, and on the other by the deep 
soil of a meadow. It was traced 3 feet in breadth, and 15 feet in 
length. At Hagdale, near Haroldswick, the chromate of iron oc- 
curs in the form of numerous thin ramifying veins, 2 to 3 inches 
in breadth, but sometimes increasing to the breadth of 5 or 
6 inches. Many masses are elsewhere observable, extending a 
few feet, and then losing themselves in a genei'al dissemination 
throughout the whole mass. The chromate of iron is also in 
some hills diffused generally in granular particles, of the colour 
and size of gunpowder. Asbestus, amianthus and talc occur in 
many places, particularly at Swinaness, near Balta Island. 
To the east of the central mass is the Diallage rock, of w'hich 
the Vord Hill of Unst is formed, and which may be traced in 
a direction of N. E. by N. to Balta Island. It is seven miles in 
length, and two miles in breadth. In the diallage pf Balta 
Island may be found beautiful specimens of asbestus, To the 
east of the diallage, from Wya Sound to Mouness, and in the 
Island of Wya, ai'e strata of chlorite-slate associated with small 
hisulated masses of diallage and serpentine ; serpentine 'alsp 
pccqrs at the Island of Half Grunie off Mouness, 
