1879.] 
President's Address. 
43 
quantities of liquid hydrocarbons, such as petroleum; both the gases and 
petroleum having been formed by the decomposition of vegetable tissue 
contained in the tertiary rocks of the islands. Several severe and paroxys¬ 
mal eruptions are on record, accompanied by earthquakes, and during these 
eruptions, the gases, which are of course inflammable, have frequently been 
ignited, but this is a very different phenomenon from the ejection of red-hot 
lava and scorke. The cones of the mud-volcanoes are composed of clay, 
derived from the beds traversed by the gas on its way to the surface, mixed 
with water, and driven out by the gas. This determination of the non- 
igneous nature of the Kamri and Cheduba mud-volcanoes coincides with the 
observations made on similar vents in upper Burma and in Baluchistan, and 
shews that the idea, so frequently put forward in geographical and geolo¬ 
gical works, that the great line of volcanoes, which traverses the Malay 
Archipelago, terminates in Rainri, is erroneous. The northernmost extre¬ 
mity of the volcanic chain in question is probably to be found in Barren 
Island, and may have some connection with the isolated extinct volcanoes 
of upper Burma and Yunan. 
There are still three other subjects discussed in different papers in the 
Records of the Geological Survey for 1878, each of which is illustrated by a 
number of the “ Paheontologia Indica” published during the year. Two 
of these subjects are intimately connected, both being stages in the investi¬ 
gation of that extraordinary series of sandstones and shales, so largely 
developed in south-western Bengal and the Central Provinces, and chiefly 
known from comprising all the coal deposits of the peninsula. This re¬ 
markable system, comprising the Talehir, Pamuda, Panchet, Mahadeva, 
Jabaljrar and other groups or series, and now known by the collective term 
of the Gondwana system, has long attracted much attention, no less on 
account of the rich seams of coal and ironstone that it contains, than because 
of the peculiarities of its fossil fauna and flora, and a discussion, by no 
means ended as yet, has arisen, as to the relations between this fauna and 
flora and those found in various rocks of Europe and Australia. 
It must be remembered that the data on which the geological history 
of the earth, as shewn by fossiliferous rocks, has been determined, chiefly 
consist of marine organisms, and that, although it cannot be positively stated 
that beds at remote spots on the earth’s surface, if containing an assemblage 
of the same or of similar organisms, are of exactly contemporaneous origin, 
yet the fact, that the succession of marine life in all countries hitherto 
examined has proved to be the same on the large scale, is in favour of the 
view, that all deposits containing the fossils of one epoch, such as the juras- 
sic, were formed at a period subsequent to the disappearance of forms of 
the previous epoch, such as the triassic'. At all events no instance is as yet 
known in which a purely older fauna occurs in a bed of clearly later date 
