March io, 192 i] 



NATURE 



59 



regard to the habit of growth of the plant and the 

 diseases to which it is liable. Although no tests seem 

 to have been made, it is suggested that on the typical 

 "ragi" soils basic slag and bonemeal would probably 

 be more advantageous than superphosphate. 



The most casual survey of the available literature 

 shows clearly that the possibilities of agriculture in 

 India are being- recognised as never before. Indian 

 soils have hitherto been starved, and much of the 

 cultivated, land has almost reached the maximum state 

 of impoverishment (D. Clouston, Agric. Journ. India, 



vol. XV.), and, consequently, it is likely to respond well 

 to manurial treatment. Fungal diseases and insect 

 pests take heavy toll of the crops, and demand much 

 investigation before they can be controlled. Never- 

 theless, the need for improvement is fully recognised, 

 and steady but slow progress in this direction is being 

 made by the patient and determined efforts of the 

 many workers who have the interests of the country 

 at heart, and the advance already made is of good 

 augury for the future. 



W. E. Brenchley. 



Precious Stdnes in 1919. 



'T^HE long and valuable series of annual reports 

 -■• on precious stones commenced by Dr. George F. 

 Kunz, of New York, in 1883 in the publications of 

 the United States Geological Survey, and continued 

 by him since 1907 in the Mineral Industry, bears 

 witness to his enthusiasm for a subject in which he 

 is the leading authority. His latest report, for 19 19, 

 has just been issued as an advance chapter (30 pages) 

 of vol. xxviii. of the Mineral Indtistry. From it the 

 following points are extracted : 



During the war period the demand for articles of 

 luxury naturally fell, but now a marked reaction has 

 set in, and sales in Paris and elsewhere already exceed 

 those of the pre-war period. Not only are a greater 

 number of articles sold, but they also command higher 

 prices. This is especially the case in the United 

 States, where the annual value of the imports of 

 precious stones is now (105,000,000 dollars in 1919) 

 more than double ever before. As with everything 

 else, the war has had far-reaching effects on the trade 

 in precious stones. Difficulties have arisen owing to 

 the varying rates of monetary exchange, labour ques- 

 tions, and the shifting of the centres of industry. 

 Efforts are being- made to discover fresh sources of 

 supply. As in previous times of great disturbance, 

 speculators and refugees acted wisely who converted 

 perishable goods and almost worthless paper-money 

 into portable and durable jewels. 



Diamond is by far the most important item. To 

 the South African output, which is controlled by the 

 London Diamond Syndicate, the new territory of 

 South- West Africa contributes 21 per cent. The total 

 production of the Union in 19 19 of rather more than 

 2,500,000 carats (about half a ton) amounts to only 

 half that for the year 1913, but the value (nearly 

 i2,ooo,oooL sterling) is actually greater, so great 

 has been the advance in price. The sales, however, 

 somewhat exceeded the production for the year, the 

 reserve stock having been drawn upon. " River 

 stones," being of better quality, command higher 

 prices; the average in 1919 was just above 13?. per 

 carat, as against 4Z. in 1915. These stones are now 

 being collected from the bed of the Vaal River with 

 the aid of diving-bell caissons and compressed air. 

 A notable diamond is one of 1500 carats ( = 300 grams) 

 found in the Premier Mine, near Pretoria, in 1919; 



it is, perhaps, a portion of the same large crystal 

 as the famous "Cullinan" diamond found in 1905. 

 New diamond fields are recorded in Kenya Colony, 

 Gold Coast, Bechuanaland, Griqualand West, and 

 Orange Free State. The Belgian Congo yielded in 

 1919 about a quarter of a million carats, whilst the 

 returns from other countries (except a small quantity 

 from British Guiana) are practically negligible. 



As a diamond-cutting centre Amsterdam still takes 

 the lead, but the industry is now being developed in 

 England, particularly at Brighton for the employ- 

 ment of disabled soldiers. More cutting is also being 

 done in America, as shown by the increased imports 

 of uncut stones, and the establishment of cutting 

 works in South Africa is under consideration. For 

 these reasons the Dutch are considering the possi- 

 bility of increasing the output from Borneo by 

 systematic mining. The Arkansas diamond field is 

 also to be explored more systematically. Besides its 

 use as a gem, diamond has many important technical 

 applications, but it is a significant fact that the 

 American imports do not show an increase in this 

 direction, the enormous increase noted above being 

 accounted for by the imports of cut, but unset, gems. 



Pearls form the next largest item in the American 

 imports. Here again attempts are being made to 

 increase the production of the pearl fisheries on the 

 western coasts of Central America, whilst the fresh- 

 water pearls of the rivers of the United States are 

 likely to be collected on a large scale. 

 ^ Corundum gems show a steady, though compara- 

 tively small, output from Upper Burma (ruby and 

 sapphire) and from Fergus County, in Montana 

 (sapphire). Opal deposits are now being successfully 

 developed in South Australia, and a new deposit of 

 "black ooal " has been discovered in New South 

 Wales. Fine examples of "fire-opal" are mentioned 

 from Western Australia. A fine mass of precious 

 opal weighing 527 grams has been found in the new 

 opal-mining district in Nevada. Mention is made of 

 the beautiful, bright blue zircons which have recently 

 appeared in the gem market, but no information is 

 given as to their source. This has been variously 

 suggested to be Ceylon, India, Siam, or Queensland; 

 it is evidently kept a secret for trade purposes. 



■ L. J. S. 



Copper Deposits of Arizona. 



AVERY complete and highly interesting mono- 

 graph on the copper deposits of Ray and Miami, 

 Arizona, by Mr. F. L. Ransome has just been 

 issued by the United States Geological Survey as 

 Professional Paper 115. These ore-bodies have 

 rapidly attained first-class importance among the 

 great copper producers of the United States. For a 

 good many years, dating back to 1880, work had 

 NO. 2680, VOL. 107] 



been carried on in this district, the small richer veins 

 being worked and a fair amount of copp>er w'on, but 

 these deposits were not of a permanent character. 

 About 1905 the attention of mining men was directed 

 (o the low-grade disseminated ore of the region, and 

 work on this commenced about 191 1. Up to 19 18 

 nearly 46,000,000 tons of this ore had been mined 

 and 490,000 tons of copper produced. The reserves 



