452 PROFESSOR HEDDLE ON 
Lothian. It is jet black, strongly magnetic, and appears free from sand or 
impurity. 
It yielded, on 1 gramme— 
Titanic Acid, ; 4 4 : ‘ 1" 
Ferric Oxide, é ; : L x 39° 607 
Ferrous Oxide, . ; : ' ; 26° 742 
Manganous Oxide, : . : 5 "6 
Lime, . ; ; 5 : ' 5 6°% 
Silica, . ‘ ; ; ‘ : 8:4 
100 +049 
Being a composition very similar to that of the bu/é of the Granton mineral. 
Under the microscope this appeared as a powder of small grains, which were 
fragmentary, with cleavages which were not flat, but somewhat hackly. Only 
one crystal was seen; this had a truncation, the face of which was an isosceles 
triangle. Along with this, there is mixed a very small quantity of non-magnetic 
grains, which were much larger than the magnetic. All of these were rounded. 
They sometimes much resembled water-worn cassiterite ;—sometimes they were 
like worn bits of somewhat rusty iron. 
A highly-magnetic blue-black iron sand, of which the individual grains are 
for the most part perfect octahedra, occurs on the south shore of Macrahanish 
Bay, Cantyre, at a spot called the Geldrens. Though there is much igneous 
rock in the neighbourhood, yet this may have come from the gneiss, and be 
only magnetite. 
MAGNETITE. 
This mineral has been several times noted as occurring in Scotland, though 
I am not aware that any analysis of Scottish specimens have been anywhere 
published. 
In glancing over the quoted localities, I find that such as are associated 
with rocks of chlorite slate, or of serpentine may be set down as correct; but 
several mistakes have been committed regarding granitic localities. 
In the Transactions of the Geological Society, vol. ii. 1814, MaccuLLocu 
writes— I should scarcely have introduced any remarks on Rona, were it not 
for the purpose of mentioning that wolfram, hitherto unnoticed in this spot, 
is found in the granite veins that traverse the gneiss of which this island is 
principally formed.” 
That Hast Rona is here referred to, and not North Rona, as quoted by 
GreEG and LeETTSoM, is shown by a reference to Blue Bay. 
