Page images
PDF

matter, which would afford excellent paddy ground if irrigated. The younger river deposits are stiictly limited to the lowlands in the Maingldn valley.

3. Extension and origin of the older alluvial deposits.—In a continuous layer the older alluvial deposits are especially found along the slopes of the hills which border the Maingl6n valley. They, however, also form isolated hills or short ranges in the centre of the valley, thus proving that they originally filled the whole valley, but became afterwards divided, probably by the action of the Nampai, which cut its bed through these deposits, only leaving them along slopes of the hills, and here and there in isolated patches in the centre of the basin. Along the slope of the hills they form a very distinct escarpment level at its surface, being in accord with that of the hills in the centre of the valley. The deposit of two strata requiring conditions so absolutely different in one and the same locality, and evidently immediately succeeding one another, forms, however, a problem which cannot easily be solved. The compact mass of the conglomerate must have been deposited under the influence of a very strong current, while the clay must naturally have been deposited in still water. That conglomerate and clay cannot have been deposited in or by one and the same water is proved by the sharp separation. If they were deposited gradually, there must certainly be found some kind of intermediate bed, from coarse gravel gradually leading to fine sand and clay, but nothing of this kind is observed, and the clay rests immediately on the top of the biggest pebbles. I believe that the Maingl6n valley formed a kind of lake on the bottom of which the Nampai deposited the bulk and particularly the heavier parts of the débris, thus forming the conglomerate, while the silt and finer material were carried away. Gradually the basin of the lake became more and more filled up, and consequently the level of the water rose. Now, there must have been a day when the bar which closed the western outlet of the lake gave way, and the water digging its way through its own deposits and carrying large quaniities of them away, thus formed the channel through which now li e Nampai runs, and through which the heavier material was transported in the tuture. Occasional high ^floods may have sometimes restored the old lake when the outlet was still narrow and was blocked, but the heavier material was no longer stored up, and the current was always strong enough to carry it away through the channels which formed in the dry season the river bed. Along the borders of the lake and wherever there was quiet water the finer material was deposited on the top of the older conglomerate, thus forming the younger clay.

I did not find any organic remains in either conglomerates or clay. That none could be preserved in the conglomerate is intelligible, but it is rather strange that no shells should have been preserved in the clay. However, they may be discovered hereafter.

4. Description of the mines.—The pits, now deserted, from which the tourmalines were dug are numerous, and those which have apparently been worked quite recently may be seen anywhere along the slopes of the valley. The place for making a pit was always chosen with a view to getting an easy and ample supply of water for washing purposes, and was so situated that the finer débris and used water could easily be got rid of. The pits are therefore all at a certain height above the present river level, while the water is brought down from higher places in channels of considerable length. It is therefore easily understood that for these two reasons the workmen can onlv exploit the conglomerate at a certain limited height. If the pits arc too high up on the slope, it is rather difficult to get a sufficient supply of water; if too low down, the water will not easily flow off. The style of work is simple enough. At first the covering clay is removed till the surface of the conglomerate is exposed. As a rule, a large piece of conglomerate is freed at once. In the pit the surface of the conglomerate measured about 250 by 105 feet. As the thickness of the clay averaged about io feet, the quantity of clay to be removed before the operations could be started was very considerable.

The water, in a channel coming from the south-east, was conducted in the back ground of the pit along the perpendicular wall of clay, to the place where it was wanted for working purposes. It was then made to run on the surface of the conglomerate and to trickle down in part of the working place, thus softening the clayey cement, so that the pebbles could afterwards be easily removed. The miner, by heaping the larger pebbles on the free room behind himself, while searching the conglomerate in front, gradually turned over the whole of the conglomerate without being obliged to carry away the large and heavy pebbles. The smaller debris was washed in baskets, the tourmalines picked out, and the remainder probably re-washed for gold. The conglomerate has been nearly completely worked out at the southern side of the pit. A few rests are still remaining as a support to the water channel. On the northern side there is still a large quantity left, but when this is worked out, either the pit will have to be deserted or the tiresome work of removing a still larger quantity of clay than in the beginning will have to be started again.

It is perfectly clear that this kind of work requires large quantities of water. The mines can therefore only be worked during the rainy season and for a short time after its termination. It is intelligible that the difficulties are therefore such as to make tourmaline mining not only a slow but also a not very profitable business, if the scarcity and the comparatively small value of the mineral be taken into consideration.

5. Old mines.~Tourmaline being a mineral which is generally associated with granite, I was of course anxious to trace, if possible, the original locality whence the specimens found in the conglomerate were derived. As all the signs pointed to the north-east as this probable source, I extended my examinations up the banks of a small river called Nyaungdauk, where at a place called Mawtunim, large deserted pits could be seen. It was stated that the Chinese had formerly worked these pits. When I visited this locality I saw a large circular pit of about 300 feet in diameter and from 100 to 150 feet deep on the slope of the hill; the walls and the bottom were, however, covered with dense jungle; on the outer side of the dry pit there were numerous smaller ones, and large heaps of refuse proved too clearly that once extensive mining operations had been going on here. I was, however, unable to find out with certainty the object of these mining operations, although I searched the refuse for a long time. The refuse consisted of pieces of granite, and, although I carefully looked for, I did not find even the slightest trace of, a metallic ore. If such had been the object, traces of it would certainly have been found. Amongst the refuse I discovered, however, numerous crystals of black tourmaline (schorl). As the hill was formed of granite, it is very probable that at tiiis place a vein yielding pink tourmaline was exploited, and that the rolled specimens of this mineral must originate somewhere in the neighbourhood of this place. It would, however, require extensive clearings to ascertain the correctness of this opinion, and I should not recommend them, considering the small value of tourmaline. A similar pit of larger size was said to exist about 2 miles higher up the stream.

Note on a Salt spring near Bawgyo, Thibaw State, by Fritz NOETLlNGi Ph.d., Palaeontologist, Geological Survey of India.

Situation of the Salt spring.—It is a rule that great faults are usually accompanied by springs following the line of disturbance. The great fault which begins near the G6kteik pass and extends probably far beyond the Salween, is no exception to this rule. Its way is marked by several springs, the water of which is more or less alkaline, and the temperature of which reaches the boiling-point in some cases. It is of course only the salt springs that are of special economical value, as under skilful management they might prove an exceedingly profitable source of revenue. For the present, only one salt spring is known, from which salt is produced by the ordinary method of evaporating the brine in cauldrons. This salt spring is situated about half a mile to the west of the village of Bawgyo in the Thibaw State; its geographical position is about 970 15' East and Long. 22° 35' North Lat. A regular well has been dug by the villagers, which is well lined with limber, and from which the brine is drawn. I have been told that there was formerly a second well, which, however, yielded so large a quantity of brine that the villagers were unable to work it, and therefore filled it up again.

2. Analysis of the brine.—The analysis of a sample of the brine taken by me and sent to Rangoon proved that one gallon contains 8,771 grains of solid residue, or12-53 per cent. I do not think, however, that this represents the average percentage of solid matter contained in the brine. The villagers stated that during the rainy season one of the cauldrons produced 2\ viss per day. During the hot season the same quantity of water produced 4 viss of salt per day. The reason of this difference is easily intelligible. During the rainy season a considerable quantity of the rain water falls into the well, thus diluting the brine, the diluted portion of which, being of course of lower specific gravity, floats on the top and is therefore extracted. During the hot season no such dilution takes place, hence the difference in the output. I took the sample on the 8th June, that is, at a time of the year when it had already rained heavily, so that the brine was already a little diluted.

Supposing the amount of solid matter to be correct, the brine would contain 5,288 grains of sodium chloride (common salt), 3,038 grains of sodium sulphate, 87 grains of calcium sulphate, and 75 grains of magnesium sulphate, to the gallon, the rest being moisture, organic matter, &c, according to the following analysis :—

( Per cent.

Sodium chloride ......... 6030

Sodium sulphate ......... 34 64

Calcium sulphate ......... roo

Magnesium sulphate o'86

Undetermined (moisture, organic matter, &c.) .... 3'30

Total . Ioo-io

Unfortunately I have only the analysis of the brine of Sadwingyi for making a comparison. Mr. Blanford states that this salt spring is one of the most productive known in Pegu. It contained 4,704 grains of salt to the gallon. Mr. Blanford does not say whether under the word "salt,' he understands the total of solid matter, i.e. sodium chloride, sodium sulphate, &c, or whether he means only the amount of sodium chloride. Supposing the word "salt" meins the amount of sodium chloride, the Bawgyo brine would contain a considerably larger quantity of salt than the richest brine known up to the present time in Burma. If, however, the amount lepresents the total of solid matter, the Bawgyo brine contains nearly double the quantity. At any rate we may consider the Bawgyo brine to be the richest now known in Burma.

3. Analysis of salt as produced by the natives from the brine and sold tn the bazaar.—The first matter of importance which the natives everywhere told me about the Bawgyo salt was, that it could not be used for food, as it had a peculiar bitter taste; consequently, it could hardly be sold in the bazaar, and 20 viss only fetched 4 annas, while the price of best imported salt was 6 annas per viss. . When tasting the salt I did not notice the bitter taste particularly, but from the mode of manufacturing the salt, by evaporating the brine till nothing but the solid matter was left, it was perfectly clear that all salts, which were contained in the brine and which have a particularly unpalatable taste, such as sodium sulphate, were contained in the "salt," and hence its peculiar bitter taste. The analysis of a sample of salt confirmed my idea. The salt as sold in the bazaar had the following composition:—

Per cent.

Sodium chloride . • . . . • ■ . .50*14
Sodium sulphate ......... 41*33

Calcium sulphate . 0*63

Magnesium sulphate, a trace ....... ...

Undetermined (moisture, &c.) 6 90

Total . 10000

4. Manufacture of the salt.—The manufacture of salt is simple enough. Every fifth day the brine is drawn from the well and filled into large wooden troughs coarsely cut out from a log; from there the brine is filled into flat cauldrons and boiled down till all the water is evaporated. The salt is then taken out, and is ready for sale. . Under an ordinary bamboo shed there are about 14 wooden troughs to take up the brine and salt, arranged in a square, the centre of which is occupied by three furnaces, each containing two cauldrons. The furnace is not constructed in any particular way; its length is about 6 feet, its height about 1 foot 6 inches, and it is of oblong shape. The front opening at one of the small sides serves for the supply of firewood, while the back opening on the opposite side serves as an outlet for the smoke. At the top of the furnace are two flat cauldrons, each of about 2^ to 3 feet in diameter; on one side of each cauldron there are two low baskets to receive the salt which is skimmed from the surface of the brine. The natives state that such a furnace does not last longer than two months; at the end of that period it is broken up, and the clay pounded and mixed with brine to extract the salt which collected in it during the boiling process. The total number of cauldrons is said to be 3o*

5. Production and working expenses.—It was extremely difficult to get any reliable information about the production, as either the natives really did not know the exact amount produced every month, or, what seems to me more likely, did not want to give me exact information for fear of being taxed. It was stated that the daily production is about five cauldrons, each yielding z\ viss of salt during the rainy season and 4 viss during the dry season. The daily production would thus range from 12 J to 20 viss. Supposing that during six months the brine yields the large, and during six months the smaller quantity, the present total annua] production would amount to 5,850 viss. Of this quantity half goes to the Sawbwa as royalty and half to the villagers as reward for their labour. The salt being sold at 82.8 per 100 viss, the total gross value amounts to R146-8. As the villagers, however, stated that the working expenses, particularly for firewood, amounted to R2 per 100 viss, the actual surplus would amount to the paltry sum of R29-8 per annum, half of which goes to the Sawbwa. Should these statements be correct, it is clear why the villagers do not like the work, as it does not pay enough in their opinion.

»

GEOLOGICAL SURVEY OF INDIA DEPARTMENT.

TRI-MONTHLY NOTES.
No. 7.—Ending 30TH April 1891.

Director's Office, Calcutta, 30th April 1891.

ltie staff of the Survey remains disposed in the following parties :—

Madras Party.—R. B. Foote, F.g.s., Senior Superintendent, Cuddapah
District.

Burma Party.Theo. W. Hughes Hughes, A.r.s.m., Superintendent, Tenas-
serim.

Fritz Noetling, Ph.d., Palaeontologist, Upper Burma.

H. Warth, Ph.d., Tenasserim.
Punjab Party.—C. L. Griesbach, C.i.e., Superintendent.

C. S. Middlemiss, B.a., 2nd Grade Deputy Superintendent. Baluchistan Party.—R. D. Oldham, A.r.s.m., 1st Grade Deputy Superintendent.

Sub-Assistant Hira Lai.
Sub-Assistant Kishen Singh.
Darjeeling and Siikim.—F. N. Bose, B.sc, 2nd Grade Deputy Superintend-
ent.

Bengal Coal-Fields.—T. D. La Touche, B.a., 2nd Grade Deputy Superin-
tendent.

Assam.—P. N. Datta, B.Sc, Assistant Superintendent.

Head-Quarters, Calcutta.—The Director; T. H. Holland, A.r.c.s., F.g.s.,

Assistant Superintendent, Museum and Laboratory.

E

« PreviousContinue »