760 
THE TROPICAL AGRICUf.rURIST. |May 1, 1902. 
syenites of Alno have suggested to Prof. Hogbom 
that perhaps the limestone may liave been a pro 
duct of the nepheline-syenite ma^jjina there. 
The author feels sure that the crystalline lime- 
stones of Ceylon have not arisen by the alteration of 
the basic lime-silicates of the pyroxene granulites, 
although Prof. Judd lias advanced this theory in 
connection with the crystalline limestones of 
Burma, wliich seem to resemble those of Ceylon iu 
many ways. 
DISCUSSION. 
Mr. Parkinson, after expressing his sense of 
the value of the paper and the. care and elabora- 
tion with which the details had been worked out, 
described the contact of granulite and limestone 
which he had seen near Matale, and remarked that 
he believed that this section proved, firstly, that 
the granulite was intrusive, and, secondly, that 
the intrusion had been attended by absorption of 
the limestone, which had locally modified greatly 
the composition of the granulitic magraa. As to 
the original nature of the limestones, he could 
say nothing ; the interrupted sills and isolated 
masses of the granulite which had been described 
were very puzzling facts, and he inclined to the 
opinion that the author's contention that ' the 
two rocks in their present condition are essen- 
tially contemporaneous' was the hypothesis moai 
nearly in accord with the fact*. 
Mr, Holland thougiit that the author's self- 
imposed task of attacking the crystalline problems 
of Ceylon deserved the liighest commendation of 
the Society, and the additional facts now published 
formed a great advance on previous work in that 
area. But he considered that the evidence otferea 
.was utterly insuthjient to establish the Author's 
Contention that the crystalline limestones had 
liehavecl as igneous rocks, anrt formed part of the 
magma which gave rise to the associated Char- 
.nockite Series. He (the speaker) had described 
primary and original calcite in a nepheline-syenite 
from Southern India, as Adams had done for 
Ontario and Hogbom for Alco ; and though he 
was convinced that calcite might be dissolved with- 
out decomposition, and subsequently separated 
from a nepheline-syenite magma in which there 
was no free silica and an excess of electropositive 
alkali, it would be impossible for a limestone and 
charnockite to come into igneous contact 
■without a chemical reaction \\h:ch would 
result in the alteration of both rocks. The 
phenomena described by the Author were 
precisely those which would be expected 
theoretically from the intrusion of a 
charnockite into a pre-existing limestone. The 
limestones liad been as a whole raised to a high 
temperature, and (as he had previously suggested 
from other evidence) had been brought to a con- 
dition probably akin to fusion, in which condition 
there would be a suftieient freedom of molecular 
movement to account for all their structural pecu- 
liarities — the inter-growths of calcite and dolomite, 
the flow-structures, and the occurrence of large 
phenoerysts of accessory minerals, which did not 
indicate an igtieons condition any more than the 
large chiastolites of chiastolite-slates. The absence 
of cataclaslic structures did not indicate freedom 
from deformation alter solidification, as Adams and 
Kicholson had proved that marble, under differen- 
tial pressure and at a temperature no higher than 
400° C., could be made to How like glacial ice 
without the production of cataclastic structures. 
The plasticity of thelimestone at temperatures well 
beluw the fu^ing-point of any ro.-k was sutheieiit 
to account for the steam-like disjiosiiion cf the iu 
elusions, as wfll as the dislocation o( the char- 
nockite-sills without internal deformation. In 
India are seen corresponding coutact-[dienomcna 
where the charnockites invade aluminous rocks 
(the k'lundalites of Walker) and siliceous rocka 
(quai zltes of various kinds), and these, like the 
limestones, have lueir nearest chemical equivalents 
among known sediments. In places these para- 
schists and paragneisses predominate over the 
orthogneisses ; while in thesouih, where denuda- 
tion has proceeded to greater relative depth", liiey 
are subor linate in quantity, and in Ci;ylon tlie 
limestones now exposed are appAiently mere in- 
clusions in the Cliarnoidvite Seiies. 
I'rof. Judd expressed hi?, gialitude to the Auliior 
for bringing forward adescription of a di-arict so in- 
teresting to geologists. The rocks described were 
similar to those of linrma, except in tlieremaik- 
.able ab-ence of certain minerals, such as corun- 
dum and its derivatives. He fuund great ditlicnlty, 
as the author did, in realizing that the 
charnockites could be intrusive in the limestones. 
In Burma and Ceylon alike, whatever mi^ht be 
the case iu Southern India, the limestones were 
remarkably subordinate to the silicate rocks, 
instead of the reverse being the case (^s we should 
expect, if the latter were intrusive in the foi nier). 
He agreed with the previous speaker as to the 
difficulty of imagining the limestones to l)ave 
behaved as ieneous rocks, and yet their relations 
with the igneous rocks were puzzhng in the 
extreme. He referred to the occurrences of Gleneig 
and Tiree as nifording fine illustrations of the 
part played in such a complex by calciphyres. 
Mr. GUEENLY remarked that in the Hebridian 
Gneisses of the North-west of Scotland there wa.^ 
also a great preponderance of igneous over wimt 
appeared to be sedimentary material. The Loch 
Mjiree Group was now generally regarded as scili- 
nientary, but it was a comparatively narrow z 'ue, 
while from Loch Maree to Cape Wrath all appealed 
to be igneous. Limestones were a conspicui.us 
feature of the Loch Maree Group, but they were 
accompanied by graphite-schists, mica-schists, and 
other probably sedimentary rocks. 
The author, in reply to Mr Holland, said th^t 
no doubt in most cases crytallines were a re- 
sult of the recrystallization of calcareous rock.s 
under pressure ; behaviour as a plastic medium did 
not involve a very high temperature, as had been 
proved by the work of Adams and Nicholson. 
But the limestones of Ceylon posssessed a num- 
ber of peculiar cliarscters which, taken together, 
suggested to him that they had existed in ' a 
state akin to fusion.' With regard to the interrup- 
ted sills, if this phenomenon was due to ' pinching' 
while both rocks were in a solid state (as Mr 
Holland had suggested), why did the narrow 
lime-silicate contact-zones completely surround the 
lenticles, instead of occurring only on two sides 
of the granulite, as in the sill itself ? Moreover, 
the accessory minerals in the lime-stones would 
show some trace of deformation if such power- 
ful earth-movements had affected their matiix. 
In reply to Mr Greenly, the author said that 
rocks composed tnainly of biotite and garnet, 
which lie regarded as of sedimentary origin, were 
scarce ; no rocks with kyanite, andalusite, 
or sillimanite were known in situ. Even if 
such exist, and are the remains of sedimentary 
recks, the igneous rock must greatly exceed 
