Aufi. 1, 1900.] 
THE TROnCAL AGRICULTURIST. 
ON CEYLON ROCKS AND GKAPHITES * 
BY A. K. C005IARA SWASIY, F.G.S. 
Ceylon is surrounded by raised beaches, and lias 
been elevated in recent geological time'* ; fluvia.- 
tile deposits also occur ; the gems for which 
Ceylon is famous are obtained from gravels in the 
Katnaimra district. With the exception of these 
recent deposits, the island probably consists en- 
tirely of ancient crystalline rocks. Pyroxene- 
j,'ran"ulites are recorded from several localities ; 
they are dark in colour and greasy in lustre. Filia- 
tion is not evident, bat it may appeiir in thin 
slices. The minerals most frequently present are 
augite or hvperstheue, or both, plagioclase 
(u-:ually labradori'.e), orthoclase-microphorite, 
garnet, quartz, nmphibole, magnetite, a;iatite, 
zircon, and hiotite— the pyroxene and felspar 
alone being essential constituents. Varieties 
approach gabbro and eclogite. Tlie texture is 
granulitic or granular. Centric structures are 
very characteristic, probably resulting fro ii the 
corrosion of c'arnets. Normal granulites are white 
or grey and "usually contain red garnets. The 
minerals are quartz, orthoclase, and microline- 
microperthite, plagioclase, and garnet ; hiotite, 
magnetite, ilmenite, apatite, and zircon are often 
present ; and the texture is granulitic. Micro- 
cline-gneiss, sometimes with hornblende, occurs in 
conical hills originating the term domoid gneiss 
employed by Prof. Walther. The minerals in- 
clude ' orthoclase and microcline-niicroperthite, 
quartz, plagioclase, biotite, pyroxene, amphibole, 
pvrile, magnetite, apatite, anil zircon. Anorthosite- 
gneiss, gneissic granite, arid pegmatite are also de- 
scribed Darkdiorites(containing amphibole, plagio- 
clase, quartz pyroxene, biotite, magnetite, apatite, 
and zircon), dolerite, hornblende-gabbro, andophitic 
quartz norite are also present. The white, crys- 
talline limestones usually contain pale mica and 
blue apatite ; sometimes also colourless pyroxene. 
Barded scapolite and woUastonite bearing ro^lcs 
are found at Galle. Certain rocks, apparently 
vein products are also described, which contain 
quartz and calcite niicrographically intcrgrown. 
Graphite occurs chiefly in branching veins in 
igneous rocks, which at Ragedara are "ranulites 
and pyroxene graiiulites. The relations to the 
matrix' are described, aiul are held to favour the 
id,-a of the deposition of the mineral as a sub- 
limation product (Walther), or from the decom- 
position of liquid hydrocarbons (Diersche). Ana- 
lyses of several of the minerals, including man- 
ganhedenbergite, are given, and a bibliography 
of the geology of the island is appended. 
DISCUSSION. 
Professor Bonney expressed his sense of the 
importance of this paper, on which he knew 
that the author had expended great labour. It 
was interesting to find so great a mass of aueic.t 
crystalline rocks pi actically unaffeeled by pressure. 
The relations oi" the garnets, felspar, anci pyioxciio 
were most interesting and suggestive, and su, 
too, was the mode of occurrence of the graphite- 
He thought the paper was very valuable as 
illustrating the formation of a root-like graphic 
structure, wdiich he thought implied crystallisation 
under obstruction, wh.ile the ordinary rectilinear 
"graphic" structure (to which the name was 
originally given) implied that one of the two 
minerals w is not resisted by the other. 
Dr. J. W. Evans referred to the resemblance 
between the rocks described in the paper and 
* Paper read before the Geological Society of London. 
those of Southern India, of which Ceylon was 
geologically an integral part. Towards the south 
of the Indian peninsula the ancient sedimentary 
rocks' disappeared, though the extensive <.'ranitoia 
gneiss still continued. The most remarkable fact, 
however, was the extraordinary development of 
tlie cliamochite series of Mr. Holland, which 
appeared to be identical with the present au- 
tlior's pyroxene-granulities. These formed the 
lofty mountain masses of the Nilgris and Anna- 
malais, and were, it seemed, the chief feature 
of the most elevated rrgious of Ceylon. Graphite 
also occurred in Soutiiern India, not only in 
dykes in Tavancore, but in flakes in holocrys- 
talline igneous rocks both in Mysore and in 
liriiish India. 
The PRESIDEXT also spoke. 
The Author stated, in reply to Dr. Evans, 
that small flakes of disseminated graphite occurred 
in several of the igneous rocks of Ceylon, He 
distinguished between the graphite occurring thus 
as a subordinate rock-fornung mineral, and the 
vein graphite which had been deposited after 
the consolidation of the rocks in which it was 
founa. In conclusion, he heartily thanked the 
Fellows tor the very kind way in which they 
had received his paper. — Mininfj Jownal, Jure 23. 
-® 
PRODUCE AND PLANTING. 
Ar.TFCii^ Japanese. — -Japanese tea dealers:-, with the 
object of securing good prices, have been diligently 
spreading reports this season of a shortage of 15 to 
20 per cent., in the first crop. It is now said to have 
been ascertained that the crop is fully np to the 
average, and even shows an excess as regards the yield 
of fine teas, considerable stocks of which are being 
held up-country. Adverse reports were also being 
circulated respecting the second picking, but here 
as;ain it is positively asserted, in contradictions of 
these reports that the conditions have been ex- 
tremely favourable to increased supplies this year, 
and that the third and fourth crops will also be 
abundant. 
The World's Rubber Supply. — The total world's sup- 
ply of rubber today is about 120,000,000 to 130,000,tlUO 
lb, vaUied at about £15,000,000. At the present time 
lactiferous plants yielding •' caoutchouc," or "rubber," 
are being worked for couimercial piu-poses in Brazil, 
Bolivia, Central America, East and West Africa whence 
coma the chief supplies, whilst Guiana, the Eastern 
Archipelago, Madagascar, India, and Ceyiou contribute 
a small quantity to the general stock. More than half 
the total supply is exported from the Amazon district. 
Owing to the recuperative power of the tree it is im- 
probable that the available supply of rubber from the 
Amazon valley will be exhausted in the near future. 
Also the enormous area over which the estates extend 
makes it unlikely that unexpected events should oc- 
cur by which the industry as a whole would be 
damaged. For the same reason, and owing to the 
sc arcity of labour, it is improbable that any very 
suuden increase or decrease of the annual production 
will occur. The tendency is at present for a slight 
increase of the total production each year. — H, and C. 
Mail, July 13. 
o . 
Cacao Fermentation.— A report as to experi- 
ments on the fermentation of cacao in Grenada 
forwarded by the Secretary of the Grenada Agri- 
cultural Society was referred to the Trinidad 
Cacao Committee with a view to local experi- 
ments of the same nature. They reported that 
there is no appreciable difi'erence in the ultimate 
weight of cured cacao by reason of a short or long 
period of fermentation. — Trinidad Agricnltural 
Journal. 
