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The coals are sub-bituminous and are entirely non-coking. Results of examination by means of heavy liquid separation of a typical sample are set out below:

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This result shows that the constitution of the coal allows of a useful amount of cleaning being done. Flotation tests indicate that the coal may be cleanable, but that the consumption of reagents will be exceptionally large because of the nature of the surface properties of this type of sub-bituminous coal. For this reason cleaning may not be profitable and the necessary research has not been undertaken.

The present relative importance of the coals dealt with in this paper can be gauged from Tables 6 and 7 from the Records of the Geological Survey of India, Vol. LV, pp. 174-175, which give the outputs of Gondwana and Tertiary coal in India respectively.

COST OF TREATMENT.

The following estimates of costs have been prepared from data supplied from England suitably amended to suit Indian conditions. The operating charges include power at 0.5 anna per unit, labour, supervision, flotation reagents, renewals, amortization, and royalty to Messrs. Minerals Separation, Limited. The figures are for a large plant designed to treat run-of-mine coal giving a clean product dewatered for coking. For simplicity it has been assumed that the remainder, or tailings, will be worthless, and that all costs are charged to the output of clean product.

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A comparison of the advantages to be gained by cleaning, and the costs of treatment, is now possible. The ash figures given in the results of flotation tests may be replaced by values in rupees per ton and the figures so obtained may be compared with the table of estimated costs given above. It will be seen that if a coal is cheap and/or capable of yielding a large percentage of clean product, treatment may be profitable. Certain of the Indian coals fulfil these conditions. It is hoped to publish further information on the whole question as work developes.

Sampling is of very great importance. Although not given in this paper all data relative to the sections of the seams have been

noted.

All the recorded results of analyses are from tests done in the laboratory of the Geological Survey of India by Babu Dulal Chand De. Calorific values given on page 244 are calculated by Goutal's formula from the proximate analyses and are sufficiently accurate for the purpose. Typical analyses are from several samples and are intended to show the differences between the different types of coals.

I wish to express my thanks to Messrs. Minerals Separation, Limited, and to Messrs. Villiers, Limited, their agents in India, for permission to publish this paper; to the several Companies who

have given valuable assistance in the field work connected with this investigation; and to Dr. Fascoe, Director of the Geological Survey of India, for his appreciation of the possible importance of this work and his very considerable help in making arrangements for the use of the laboratory in his charge.

BIBLIOGRAPHY.

BALL, V. AND SIMPSON, The Coal-fields of India. Mem. Geol. Surv. R. R.

BURY, E., BROADBRIDGE,

W. AND HUTCHINSON,
A.

JONES, F. BUTLER

66

Ind., vol. XLI, part 1.

Froth Flotation as applied to the Washing of Industrial Coal." Trans. Inst. Min. Eng., vol. LX, part 3, pp. 243-253.

"The Froth Flotation of Coal." Proc.

South Wales Inst., Eng., no. 4, vol. 37,
September 24th 1921, p. 331.

HUGHES, F. CUNYNG- Proximate Analyses and Calorific Values of

HAME.

LESSING, R.

STOPES, M..

THAU

TIDES WELL, F. V. AND
WHEELER, R. V.

WOOD, L. A.

Bengal Coals. Trans. Min. Geol. Inst.
Ind., vol. V, pp. 114-161.

"Behaviour of the Constituents of Banded
Bituminous Coal on Coking-Studies in the
Composition of Coal." Journ. Chem. Soc.
Trans., vol. CXVII, p. 247.

"On the Four Visible Ingredients in Banded
Bituminous Coal-Studies in the Composi-
tion of Coal, No. 1.'

66

Series B, vol. XC, p.

June 1922, p. 93.

Proc. Roy. Soc.

470. Fuel, 23rd

'Refining Coal, with special Reference to the Production of Coke low in Ash.' Stahl und Eisen., Nos. 30 and 32, 1922.

"A Chemical Investigation oi Banded Bituminous Coal-Studies in the Composition of Coal." Journ. Chem. Soc. Trans., vol. CXV, pt. 1, p. 619.

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Some Aspects of Cleaning Coal by Froth Flotation." Cleveland Inst. Eng., 1922-23, pp. 13-33.

SUBMARINE MUD ERUPTIONS OFF THE ARAKAN COAST, BURMA. BY J. Coggin BROWN, O.B.E., D.Sc., Superintendent Geological Survey of India. (With Plate 17.)

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INTRODUCTION.

N the charts of those parts of the eastern shores of the Bay of Bengal, known as the Arakan coast, the following caution to navigators appears -

"Mud volcanoes, which occur in the sea, frequently raise islets which may remain above water for some time or quickly sink, leaving dangerous shoals in their places, and a constant and careful look-out is necessary when navigating this coast."

The mud volcanoes of Ramri and Cheduba Islands were first systematically investigated by F. R. Mallet1 in 1878, and a comprehensive summary of his account has been given by R. D. Oldham in the second edition of the Manual of the Geology of India.

Underlying the shallow waters of the eastern shores of the Bay of Bengal and stretching north and south of the islands already mentioned, there are other localities from which gas, oil and mud are ejected from time to time, sometimes quietly and without any marked disturbance, but, occasionally, with explosive violence, recalling the spasmodic paroxysms of the Cheduba mud volcanoes which distinguish them from others found elsewhere in the oilbearing regions of Burma.2

In the words of Dr. E. H. Pascoe 3,

"It cannot be too emphatically denied that in Burma the so-called "mud volcanoes have anything whatever to do with volcanic phenomena. They are entirely due to the escape of gas, the mud and rock fragments being purely accidental accompaniments, and constitute a perfectly normal part of the hydrocarbon occurrences in the oil-belts'. There is every gradation between a small insignificant oil or gas scepage and the conspicuous mounds or cones like those on the Arakan Coast, whose terrific outbursts afford some excuse for their having been mistakenly attributed to volcanic disturbance."

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1 F. R. Mallet: "The Mud Volcanoes of Ramri and Cheduba"; Rec., Geol. Surv. Ind., XI, pp. 188-207, (1878).

2 R. D. Oldham: "A Manual of the Geology of India," pp. 20-22 (1893).

3 E. H. Pascoe: "The Oil Fields of Burma"; Mem., Geol. Surv. Ind., XI, p. 211, (1912).

The eruptions of the submarine mud volcanoes give rise to the new islands which appear at intervals off the Arakan coast and add to the ordinary perils of these seas.

Apart from the desirability of recording the occurrences for the benefit of navigation, they are of great interest from other points of view, especially for the light they throw on the geology of this part of the Bay of Bengal. To quote Dr. Pascoe again,

"Their latitude and longitude, for instance, would fix points of probable anticlinal crests. The time of the year at which they occur and even the state of the tide probably have some bearing upon the underground conditions giving rise to the eruptions. Samples of the ejectamenta are of course useful, especially if they should happen to be fossiliferous, since they might be recognisable fragments of known types of rock."

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To these suggestions may be added others, such as the vexed question of the means by which the emitted hydrocarbons occasionally become ignited and give rise to fiery eruptions far out at sea, and the connection, if any, which exists between the times of eruption and seismic disturbances elsewhere, for although in their origin they are not associated, contrary to public opinion, with either volcanoes or earthquakes, it has been suggested that the convulsive outburstø are sympathetic responses to seismic disturbances, that an earthwave may, in fact, act as a hair trigger and detonate the underlying unstable system in which the "mud volcano" is initiated.

In 1885, Mallet published a list of the eruptions which had taken place up to that date. A later one happened on Cheduba Island on 3rd July, 1886.3 From that time until October, 1893, there are no records of any other disturbances of the group. Accounts of later eruptions have appeared in the Records from time to time until 1912.4

1 E. H. Pascoe. "The Oil Fields of Burma"; Mem., Geol. Surv. Ind., XI, (1912).

p. 188. 2 F. R. Mallet, "On the alleged tendency of the Arakan Mud Volcanoes to burst into Eruptions most frequently during the Rains"; Rec., Geol. Surv. Ind., XVIII, pp. 124-125, (1885).

3 F. R. Mallet: "Notice of a Fiery Eruption from one of the Mud Volcanoes of Cheduba Island, Arakan ;" Rec., Geol. Surv. Ind., XIX, p. 268, (1886).

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J. Coggin Brown: "Recent Accounts of the Mud Volcanoes of the Arakan Coast, Burma"; Rec., Geol. Surv. Ind., XXXVII, pp. 264-279, (1908); Supposed Eruption of a Mud Volcano in the Straits of Cheduba, Arakan Coast, Burma." Rec., Geol. Surv. Ind., XLII, pp. 54-56, (1912); "Eruption of a submarine mud volcano off Sandoway, Arakan Coast, Burma." Rec., Geol. Surv. Ind, XLII, p. 278, (1912); Fiery Eruption of a Mud Volcano on Foul Island, Arakan Coast, Burma." Rec., Geol, Surv. Ind., XLII, p. 279, (1912).

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