138 GEOLOGY. 



gneiss, of the oldest known series in India. Many details of several of 

 the reefs arc given, as well as an estimate of the prospects of mining. 



F.J). 



Mallet, F. R. On the Geology and Mineral Eesources of the Dar- 

 jiling District and the Western Duars. Mem. Geol. Surv. Ind. 

 vol. xi. 96 pp., 2 maps. 



The area described is a portion of the Himalayas (between the Terai 

 and Sikkim) bounded by Nepal on the W. and Bhotan on the E. The 

 outermost hills are of the soft sandstone and clunch of the Nahun beds 

 (Tertiary). Going northwards, these appear to dip under, but probably 

 dip against, the older rocks ; these latter are, first, Damuda beds some- 

 what altered — alternations of sandstone and quartzite, shales, slates, and 

 beds of anthracitic coal. Overlying these, without apparent uncon- 

 formity, are some thousand feet of slates, which pass, as one ascends 

 the hills, through mica-schist into gneiss; the more metamorphosed 

 strata, here as in some other places, overlying those less altered. These 

 slates, schists, &c. are named the Doling series. A mass of variegated 

 slates, differing considerably from these, and containing, besides thick 

 bands of quartzite, a bed of dolomite 1500 to 2000 feet thick, is named 

 the Baoca series ; it underlies the Baling. A detailed vertical section 

 of several hundred feet of the Damudas shows them to be composed of 

 sandstone and shale alternating in thinnish beds, with several seams of 

 coal, generally under a foot, but in one instance 5| feet thick. The 

 finest coal-seam yet found is 11 feet thick. The author inquires into 

 the feasibility of correlating these with the Damudas of the Raniganj 

 field, and is inclined to put them with the " Eaniganj " rather than the 

 " Barakar " group. He discusses the probability of finding a coal-field 

 of the Damuda series beneath the Gangetic alluvium, and concludes 

 that though its existence is not improbable, it would not be wise to 

 bore for it in the present state of the manufacturing industries of 

 India. Of the Baxa beds a section is given showing between 5000 and 

 6000 feet, with the base not seen ; the relation of these to the Damuda 

 is obscure ; but the Baxa beds are seen to underlie the Daling beds 

 without sensible unconformity. Also where the Daling beds rest on the 

 Damudas there is no sensible unconformity, but a very marked and 

 sudden lithological change. The Daling beds change upivards into 

 gneiss, which is here called "Darjiling" gneiss. 



Some details of the Tertiary beds are also given. Under the heading 

 " Economic Geology," analyses of the coal are given, which show it to 

 contain 70 p. c. or less of free carbon, 9 to 12 p. c. of volatile matter, 

 and from 13 to 25 p. c. of ash ; it is described as an " anthracitic coal," 

 not anthracite : the question whether it could be worked with advan- 

 tage is gone into ; the author points out various drawbacks, especially 

 the crushed and contorted state of the beds, but thinks that the seams 

 are worth a fair trial. A bed of brown iron-ore, containing 30 p. c. 

 of iron, has been found, as well as some magnetite and specular iron. 

 The last two may ultimately become valuable for working on a larger 



