^{page 465 note 1} On the Geology and Coal Resources of Korea State, Central Provinces, Mem. Geol. Surv. Ind., xli, p. 180 (1914).Google Scholar

^{page 465 note 2} Proc. Roy. Soc. London, Ser. B., vol. xc, 470–486 (1919).Google Scholar

^{page 467 note 1} On the Relationship between the Specific Gravity and Ash Contents of the Coals of Korea and Bokaro: Coals as Colloid Systems, Rec. Geol. Surv. Ind., lx, 313–357 (1928).Google Scholar

^{page 467 note 2} On the Specific Gravity and Proximate Composition of some Indian Vitrains, Rec. Geol. Surv. Ind., lxii, 189–228 (1929).Google Scholar

^{page 467 note 1} On the Specific Gravity and Proximate Composition of some Indian Durains, Rec. Geol. Surv. Ind., lxiii, 358–377 (1930).Google Scholar

^{page 467 note 2} I find that prior to this H. Potonié noted the colloidal nature of humus in his work, Die rezenten Kausto-biolithe u. ihre Lagerstätten, Abhandl. d. K. Preuss. Geol. Landesanstalt, Neue Folge, Heft 55, ii, p. 3 (1911).Google Scholar Further, Stopes and Wheeler in their paper on the “Constitution of Coal”, Dept. of Scientific and Industrial Research, p. 19 (1918)Google Scholar, mention, H. Winter as believing in the colloidal nature of coal, quoting Gluckauf, 49, 1406–1413 (1913).Google Scholar

^{page 467 note 3} X-Ray Study of Coal, Ind. Journ. Physics, iv, 79–98 (1929)Google Scholar; X-Ray Study of Vitrains, v, 525–541 (1930).Google Scholar

^{page 468 note 1} The Indian durains studied by me contain on the average nearly 35 per cent of “ash contents” in colloidal association.

^{page 468 note 2} See the quotation from my 1914 paper given above.

^{page 469 note 1} Previous references to these veins are contained in Mr. Willbourn's Report of the Geological Survey Department for the year 1936, p. 12Google Scholar, and MrWillbourn's, corresponding report for 1937, p. 22.Google Scholar

Analyses are given of samples from the Lai Chak mine at Semoliang, but as specific gravities were not determined those analyses are not quoted here. They differ from the analyses of coal from the Heng Bee Kongsi's mine given in my paper in showing higher moisture and volatile matter and much lower fixed carbon.

The following passage in the latter report relating to the Heng Bee Kongsi's mine is quoted here:—

More recently, several veins have been exposed in a mine worked by the Heng Bee Kongsi on lot 3329. They are of particular interest, in that, besides traversing the alluvium, they extend also into the schist bedrock, and penetrate it to a variable depth, occasionally as much as 10 feet. The majority are from 1 to 3 inches thick, and some can be traced for a distance of 100 yards. The lignitic coal must be of recent origin, because one vein was noted to pass through the bark of a piece of wood in a peaty layer in the alluvium, only 6 feet below the surface. Clearly, it cannot be more than a few thousand years old, and may be much younger.

These veins of lignitic coal are now known to occur near Bidor, Tapah Road, Malim Nawar, and near Taiping at Asam Kumbang. Their origin is still in doubt.

These occurrences are also referred to on p. 70 of Dr. Ingham's recently issued memoir on The Geology of the Neighbourhood of Tapah and Telok Anson, Perak, Federated Malay States, with an account of the Mineral Deposits, 1–72 (1938).

^{page 470 note 1} The following is a note on these veins in the Heng Bee Kongsi, kindly provided by Dr. Ingham:—

“In this mine there is alluvium, usually from 10 to 20 feet thick, overlying bedrock of weathered schist and phyllite. These are usually white or pale green in colour owing to the bleaching by weathering of the black graphitic schist, which in places is exposed in depth. The age of the bedrock is believed to be Permo-Carboniferous”

“Several veins of lignite, more or less vertical and having generally a width of from 1 to 4 inches, traverse the alluvium, and individual veins have been traced for a distance of 100 yards. Some extend upwards from near the base of the alluvium to end before its surface has been reached; it is not known that any vein actually reaches the surface. Some veins extend downwards beyond the base of the alluvium and actually into the extremely ancient schist-phyllite country, which they penetrate to a depth of approximately 12 feet in some parts of the mine.”

“There is a tendency for neighbouring veins to be parallel with one another, but the veins in one mine are orientated quite differently from those in another”

^{page 471 note 1} The Siwalik vitrains of Kashmir are exceptions to this rule. One specimen with 14·35 per cent of moisture falls into the group with “most brilliant” lustre, and another with 15·81 per cent of moisture into the “less brilliant” group.

^{page 472 note 1} A less probable source is the graphite that was formerly in the bed-rock schist at one mine.