282 
THE TROPICAL AGRICULTURIST. (October i, 1887. 
w hich overlies the granite. The igneous rock, 
a ecording to the received theory, pushed up the 
stratified rock, gneiss, from the ooean in which it 
had slowly formed, the gneiss in its turn pushing 
up beds of crystalline limestone (dolomite), 
which had formed, also in the ocean, over 
the surface of the gneiss. These are our three 
prinoipal and primitive rocks, gneiss being 
king of all. Indeed, some have held the view 
that true granite where in contact with its 
allied rock, has been compelled to enter on 
the metamorphic processes, which have given 
gneiss such protean shapes, colours and con- 
ditions. While granite is being metamorphosed 
into gneiss at one end of the scale, gneiss de- 
caying from the action of the atmosphere on 
superabundant felspar, is, at the ether forming 
new combinations, and giving us the valuable 
laterite locally known as cabook (sometimes 
called iron clay) ; good as blocks for building 
purposes, as gravel for road material, and as it 
is further acted on by the atmosphere and 
man's agency, the foundation of our most fertile 
soils. The characteristics of thit-: curious product 
of gneiss will be thoroughly discussed and settled 
before the discussion on its failure as a founda- 
tion for the Maligakanda reservoir closes. We 
may just notice in passing that while the red 
colour produced by peroxide of iron distinguishes 
some of our very richest soils, oxides of iron in 
Other shapes are charged with the strangely 
contrasted barrenness which distinguishes our 
upland patanas ^mountain prairies or savannahs) 
from the rich forests from which they are in 
most cases so sharply divided. The superabundant 
iron in Ceylon was formerly utilized by the natives, 
many furnaces and much slag being scattered over 
the land, but now the imported metal has put an 
end to all local manufacture. Felspar, besides 
leading to the decay of gneiss and its transmuta- 
tion into laterite, is the origin of the beds of 
kaolin or China clay, pretty common in our hill 
system, and also of the very pretty but not 
intrinsically valuable moonstone, with its semi- 
pearly lustre. The more kaolin in the rock, the 
more potash in the soil. When coffee was our 
great cultivation the quantity of lime contained 
in our gneiss-derived soils was deemed deficient 
either for fertilizing purposes or for keeping the 
clay soils mechanically free. But for tea cultiva- 
tion the stiffness of our clayey soils and the large 
proportion of ferruginous constituents in them are 
not disadvantageous. The strong taproot of the 
tea plant opens up the stiff clay subsoil, while 
the presence of iron in quantity not deemed 
beneficial for coffee, seems to suit tea admirably. 
The mineral constituents of our soils and the 
proportions of humus and other organic matter 
vary considerably, but of late years the tendency 
of opinion is that the fertility of our Ceylon soils, 
especially those of the mountain region (about 
one-sixth of the whole), has been considerably 
unde ( Btimated. Tea, at any rate, seems to grow 
Will in all local tics, where the rainfall exceeds 
70 irches per annum. The disintegrating and 
denuding effect of the tropical heat and violent 
monsoon rains t n our mountain gneiss formation 
is very marked, and the slow rise from below 
belived to be going on is quite necessary to 
preserve the equilibrium. Curiously enough the 
presence of garnets in our gneiss, and much of 
it is excessively garnetiferous, seems to promote 
decay as much as exefss of felspar does. Large 
nnd most beautiful bard specimens of rock spark- 
ling >'itli garntts were obtained from the centre 
of I he great slip which recently took place on 
railway. Ak b gem, the red garnet is not 
found so as to be of special value, but " ciDnamo 11 
stones" are amongst the common preciouB stones 
of the island. The fine blue sapphires for which 
Ceylon is so famous, rubies (the same stones 
ouly differently coloured) and most of our gems 
are derived from decomposed gneiss, being crys- 
tallized clay generally, but our second primitive 
rock, the crystalline limestone, is in some cases 
as at Matale and in Uva, bright with spinel sap- 
phires. The mountain limestone is generally too 
largely composed of magnesia to be of good 
quality for building or agricultural purposes, but 
in some places it exists as an almost pure car- 
bonate of lime, fit to be usefully polished into 
marble, and burnt into lime for whitewash and 
cement or as a soil fertilizer. Our harder forms 
of gneiss can also be beautifully polished ; frr 
instance that quarried at Mahara for the grand 
Colombo Breakwater. A polished column in the 
Museum, in which grey, black and green tints 
are harmoniously combined, is much and deservedly 
admired. Equally beautiful, when properly polished, 
are specimens of the red granite or granitic gneiss 
which is found a few miles distant from this 
quarry south of Henaratgoda. Swallow and bat 
oaves exist in the gneiss f jrmations, as well as 
in the limestone, but nitre forms chiefly in the 
limestone caves, we believe. The soils of the 
regions of outlying hills, standing in small ranges 
and detached masses, beyond, sometimes far distant 
from the limits of the mountain zone, differ 
essentially from very poor in some portions of 
the south-west to very rich in the north and east. 
Between the vast boulder of Dambulla for instance 
and the hill of Mihintale near Anuradhapura, the 
soil is rich to a degree, wanting only irrigation 
water to restore it to its ancient fertility. Ten- 
nent's theory is that Sigiri, Mihintale and other 
detached hills were " shot up " as they stand, 
when our mountain system, with the centre of 
activity near Adam's Peak, was upheaved. Mr. 
Campbell, in looking from Dambulla rock over 
the vast eastern and north-central pliin, imagined 
the action of an ancient ocean striking against 
the cave rock. But during a recent tour in this 
region we looked in vain for traces of marine 
remains, and our inclination is to regard Sigiri, 
Mihintale and the mysterious range of Ritigala 
as the surviving remnants of a mountain and hill 
system which once covered the larger portions of 
the island, the rich soil of Nuwarakalawiya being 
the result of the decomposition of the softer 
gneissic rocks. Our theory must be taken at what 
it may be deemed worth. Other theories, while 
questioning any closer junction with the Indian 
continent than now exists, represent Ceylon as 
having been part of a region which stretched to 
the Maldives on the one hand and to Sumatra 
on the other. Tradition on the other hand points 
to vast subsidences. Populous places which have 
left no trace are stated to have been submerged 
off the west coast of Ceylon, while the Basses 
Itouks, on the south-east coast of the island, are 
supposed, apparently with good reason, to be the 
remains of a greater Lanka then now exists. 
There is a sudden sinking of the sea bottom to 
great depths at Trincoiiiaiee on the east coast and 
also in the Gulf of Mannar, supposed to indicate 
ancient earthquake action and subsidence. There 
is, apparently, no evidence of recent volcanic action 
in Ceylon, and the hot wells which exist are said 
by some to be due to the chemical action of 
subterranean vegetation, rather than to any vol- 
canic products. But here we are on doubtful 
ground. Basalt seems certainly to exist in Ceylon, 
but in a very altered condition. We have already 
noticed the existence of veins of plumbago. It is 
