58o 



NATURE 



{Oct. 20, 1881 



The actual mines are in the soutliern part of the Madras 

 presidency, in the districts of Kadapah, Karnul, Kistna, 

 and Godaveri. The second great tract, further to the 

 north, lies between the Mahanadi and Godaveri rivers, 

 the chief localities being at Sambalpur and Weiragud, 

 eighty miles south-east from Nagpore, and at a few places 

 in Chota Nagpore. The third great tract is in the vicinity 

 of Panna in Bandeldiand. In addition to these a few 

 small diamonds are reported to have been found near 

 Simla. In all cases the diamonds appear to have been 

 found in sandstones or conglomerates, or in the gravels 

 derived from their alteration. These sandbtones are re- 

 ferred in the southern localities to the lowest member of 

 the Karnul formation, whii-h as a whole is considered to 

 be the equivalent of the lower part of the so-called 

 Vindhyan formation of Northern India. An upper group 

 of the litter, the Rewah conglomerate, being the diamond- 

 bearinj bed in Bandelkhand. There does not appear to 

 be any authenticated instance of a diamond being found 

 in India in other than sedimentary rocks. One case, 

 however, at p. 49, where the matrix is said to be "a net- 

 work of strings of calc spar inclosing laminae and small 

 lumps of green clay," suggests the possibility of the 

 material in question being a decomposed basalt or basaltic 

 tuff, and as such comparable with the South African 

 occurrences. What the present total production of the 

 mines may be we are left to guess ; as far as can be 

 gathered from the scattered notices collected by the 

 author, the larger number of the mines are of historical 

 interest only. 



The second chapter, that on Coal, is mainly an abstract 

 of the communications on this subject made to the Records 

 of the Geological Survey of India by IVIr. Theodore 

 Hughes, and is rather behindhand in point of time. The 

 latest information appears to refer to the year 187S-79. 

 The arguments for and against the supposed Mesozoic 

 age of the Indian coal-bearing rocks are given in abstract 

 with great fairness, and the author's conclusion that 

 "floras alone form an unsafe guide to the correlation " of 

 the ages of ro?ks in different countries is probably the 

 only safe one that can be drawn from the available evi- 

 dence. As a mere question of stratigraphical position it 

 is probable that these rocks represent the uppermost coal- 

 measures (Permo-Carboniferous) of Europe. Any one 

 acquamted with the smaller coal-basins in the south of 

 Europe cannot but be struck w ith the numerous analogies 

 between them and the Indian coal-fields, more particularly 

 in the thickness and irregularity of the seams. The 

 author's statement that the Ramgunj coal "may be 

 described as a non-caking bituminous coal,'' is rather too 

 general. It is true for the larger seams, but besides 

 these are to be found others in which the caking property 

 is as well developed as in any caking coal in the world. 

 The coke produced is not of particularly good quality, 

 which is however due to the large quantity of ash in the 

 coals, but as to their caking capacity, there can be no 

 doubt whatever. The estimation as to the quantity of 

 coal available seems to be rather wild guesses in some 

 cases, and one of these, for which the data are pro- 

 fessedly given, is a good specimen of an arithmetical 

 puzzle. They are as follows (p. 69) : — 



"The coal occurs in three principal seams . . . average j 

 total thickness of 16 feet . . . over an area of 8i square 



miles. The amount of coal may therefore be estimated 

 at 1,360,000,000 tons, and the available portion of this at 

 80,000,000." 



How the largest of the above figures is obtained, and 

 what its relation to the smaller quantity may be, is 

 certainly not apparent from the author's statement. An 

 allowance of 94 per cent, for faults, waste, and unwork- 

 able coal, which the above figures lead to, seems rather 

 large. 



The chapter on Gold contains extracts from most of 

 the published details on the occurrence of precious metals 

 in India down to the Reports of Mr. Brough Smyth, and 

 the latest remarks of Indian newspapers, which latter 

 however are dated as far back as May, 1S80. An original 

 investigation of the author's as to the distribution of 

 auriferous detritus in areas occupied by rocks of different 

 characters is of interest. He found that the proportion 

 of gold obtained was larger upon crystalline schists than 

 upon gneiss and granite, a result which agrees with that 

 generally obtained in other parts of the world. As this 

 was predicted to him by his native workmen, it is difficult 

 to see how the author arrives at his belief that gold 

 washing in India affords an example of human degra- 

 dation. 



His evidence seems rather to show that the gold 

 washers have a highly skilled and minute knowledge of 

 the distribution of gold-bearing alluvia, but the value of 

 such knowledge is diminished by the circumstance that 

 the amount of such material available has been practically 

 exhausted by the labours of many generations of workers 

 through a period of 2000-3000 years. The great extent 

 of old workings discovered in some of the Wynaad mines 

 also shows that the " old men " were no contemptible 

 workers as vein miners. 



In the earlier part of the volume the work done by 

 "amateurs" in Indian geology is somewhat pointedly 

 contrasted with that of the " professionals," whose whole 

 time is devoted to the subject. This is to be regretted, 

 as is also the assumption of an air of finality for the work 

 of the Indian Survey, which the nature of the work cer- 

 tainly does not allow. For instance, we are told in the 

 same paragraph that the rock;, of the Vindhyan formation 

 are absolutely azoic, and that they may be of any age, from 

 Lower Silurian to Carboniferous ; the real meaning of this 

 expression being that no fossils have as yet been found in 

 them. In this sense the New Red Sandstone might be 

 said to be azoic over a great part of the central plain of 

 England. The results of the Indian Survey are of great 

 value as furnishing a broad outline of the stratigraphical 

 features of the peninsula, but there will be work enough 

 and to spare for both amateur and professional for many 

 years to come before that outline is moderately filled in 

 detail. H. B. 



OUR BOOK SHELF 

 The SUtdenVs Handbook of Acoustics. By John Broad- 

 house. (London: William Reeves, 1881.) 

 We are not quite sure what the title of this work is. The 

 title just given is from the lettering on the back. Within 

 the covers appears a second title, " Musical Acoustics," 

 and on the actual title-page appears the triple announce- 

 ment, "The Student's Helmholtz," "Musical Acoustics," 

 and " The Phenomena of Sound as connected with 



