of Edinburgh, Session 1881-82. 
549 
3. Chapters on the Mineralogy of Scotland. Chapter VII. 
By Dr. Heddle. 
In the present chapter Dr. Heddle considers the ores of man- 
ganese, iron, chromium, and titanium. 
He finds that almost all the manganese in Scotland occurs in the 
form of an ore of little value — -psilomelane. 
Iron, he has observed in minute laminable specks, in the free or 
metallic condition, at two localities, hut sheathed in both cases in 
magnetite. The quantity was too small for determining the presence 
or absence of nickel, but he conjectures that these specks may have 
been minute meteorites, which had fallen into the ocean in which 
the rock was being formed. 
He has found two ores of iron new to Britain, — turgite and mar- 
iite , — the one near Oban, the other in Bute. 
A series of analyses of ilmenites and of iserines or “ titanic iron 
sands ” are given ; and, as a result of a consideration of the modes 
of occurrence, and of the microscopic features of these minerals, Dr. 
Heddle concludes that they are specifically distinct; the former 
being of chance occurrence in metamorphosed rocks, while the 
latter is an almost invariable constituent of igneous rocks. 
Ilmenite he finds to be very common in Scotland, but to be, for 
the most part, confined to chloritic and quartzose bands of meta- 
morphic rocks. 
He finds that magnetic “black sands” are not unfrequently 
chromiferous, and that to a considerable extent. 
4. On the Dimensions of Cast Iron at various Temperatures, 
with more especial reference to the Phenomena of the 
Solid floating on the Molten Metal. By W. J. Millar, 
C.E., Secretary, Inst. Engineers and Shipbuilders in 
Scotland. 
1. In experimenting from time to time on the floating of solid 
metal on molten metal, the author has observed various phenomena, 
of which the present paper is descriptive, and this more especially 
with regard to cast iron and the well-known property of the solid 
