PART 2 .] 
Mallet: Mad volcanoes of Udmri and Ckeduba. 
205 
light earburetted hydrogen, mixed perhaps with the vapor of the most volatile 
liquid petroleum hydrocarbonsd Bubbles of this gas are given off from the mud 
cones in their ordinary state, as well as from most of the petroleum wells. 
There are two of the latter at Letaung, about 25 and 40 feet deep, from which 
the issue of gas is so considerable that it can be heard bubbling up when standing 
some yards away from the mouth. I roughly guessed the amount at a cubic foot 
every few seconds, and the villagers say that the well has been in its present state, 
without diminution of either oil or gas, for many years. Here the g’as is being 
continuously and quietly evolved. The quantities that (having probably gradually 
accumulated in fissures during long periods) are suddenly liberated during violent 
eruptions of the volcanoes, may be inferred from the foregoing records. 
Eecollecting the great tension at which quantities of gas are often stored 
up in coal mines, and the force with which it escapes from the ‘ blowers ’ 
there, as well as from many bore-holes in the oil regions of America and else¬ 
where, it is not difficult to conceive that in some cases gas mud volcanoes may 
be caused, where the other necessary conditions are present, by the pressure of 
gas due merely to its continued slow generation from carbonaceous matter at the 
normal temperature of the strata at moderate depths. But given certain coal¬ 
er lignite-bearing rocks, producing oil and gas; if they are situated on a lino 
of volcanic heat (although of low intensity, insufficient to fuse, or materially 
alter, the rocks accompany such carbonaceous matter), the tension of the gas 
and vapor may, doubtless, be greatly increased by the larger proportion of gas, 
compared to that of oil, produced at the higher temperature, and by the increased 
tension due to a higher temperature, where gas is stored up in a fissure of given 
capacily. In this connection the difference between the petroleum of the 
In-awadi valley and of Ramri may bo noticed. The mud volcanoes of the 
former region have been described by Dr. Oldham as very sluggish, and as never 
exhibiting the fiery paroxysms to which those in Ramri are subject. At the same 
time the oil is dark colored, is as thick as treacle, or even solid, at 60° F., being 
indeed often spoken of as ‘Rangoon tar,’ and contains paraffine to the extent 
sometimes of more than 10 per cent. The Ramri oils are associated with much 
gas, and are themselves sometimes as transparent and light colored as brandy. 
They have a lower specific gravity than the above, and at 60° are perfectly 
mobile. Without venturing to assert that the above differences are due to a 
difference in the temperature at which the oils have been produced,*^ it may 
be noticed that at Baku on the Caspian, where there are mud volcanoes 
* Whether the temperature of the emitted gases from the Ramri salses is ever sufficiently 
high to allow of steam playing any important part is a question as yet undetermined. Amongst 
other mud volcanoes which are intimately connected with petroleum may he mentioned those of 
Java; those near the eastern shore of the Caspian; at Baku; .and near the entrance to the sea of 
Azov; those near Girgenti in Sicily; and along the northern flanks of the Apennines hy Modena 
and Parma, and those in the Island of Trinidad. 
“ The occurrence of fragments of unaltered lignite amongst the ejecta from tlie Ramri 
volcanoes, although one amongst many indications that the subterranean temperature is far 
below that beneath fusion volcanoes, does not necessarily prove that the temperature may not 
he considerably above the normal one for the depth, as such fragments may have been torn from 
the upper part of the vent. 
