388 



NATURE 



[March 23, 1922 



shows that stomata are regulatory in their action, a 

 fact on which earher investigations had thrown some 

 doubt. It indicates that there are considerable 

 fluctuations in the water-content of a normal leaf, 

 and that the regulation of water-loss by the stomata 

 is very effective when they are nearly closed. 



Silk Weavers and their Output.^ — In Report 

 No. 17 of the Industrial Fatigue Research Board, 

 Mr. P. M. Elton analyses the differences in the output 

 of individual silk weavers. Silk weaving is a highly 

 skilled occupation, and it takes at least two years to 

 teach a girl to weave quickly and well. Hence it is 

 very important that unsuitable girls should not 

 waste their own time, and that of their employers, in 

 undergoing training. Training has often been faulty 

 in the past, and in consequence bad methods of 

 work are acquired which are never eradicated. So 

 important is the human factor for success in silk- 

 weaving that the quickest operatives consistently 

 produce about twice as great an output as the slowest. 

 Mr. Elton analyses the causes of these wide variations 

 in detail, and his report should be of great value to 

 those engaged in teaching young weavers. A weaver 

 has to have good eyesight, be dexterous with both 

 hands (for in weaving both hands are simultaneously 

 employed on very different operations), and have a 

 delicate sense of touch. Mr. Elton has not en- 

 deavoured to determine the most suitable tests for 

 would-be apprentices to the weaving industry, but 

 there should be no difficulty in the choice of some 

 of the necessary tests. A thoroughly adequate 

 selection can only be made gradually, after much 

 experiment, but few more fertile fields for the applica- 

 tion of the principles of " vocational selection "[can 

 offer themselves than that of weaving. 



Electrical Precipitation in Industry. — In the 

 Journal of the Society of Chemical Industry for 

 February 15, Dr. H. J. Bush gives an account of the 

 industrial applications of electrical precipitation. In 

 1884-86 Sir Oliver Lodge carried out experiments on 

 the electrical deposition of fog and smoke, and 

 patents were taken out in England and other coun- 

 tries during those years. In 1884 Dr. Karl Moeller, 

 in Germany, obtained an independent patent. In 

 1906, Dr. F. G. Cottrell, Director of the United 

 States Bureau of Mines, then professor of physical 

 chemistry in the University of California, repeated 

 Lodge's experiments in connection with the removal 

 of acid mists, and in his hands the process has been 

 largely developed. During the war a very large 

 Cottrell plant was in operation at the Queen's Ferry 

 works, and an installation was designed by the 

 Lodge Fume Co. for cleaning blast-furnace gases. 

 Dr. Bush gives an account of these and other plants. 

 The principle is very simple. An insulated wire 

 hangs inside a metal tube, both being connected with 

 a high voltage transformer, or special electrodes are 

 hung between metal plates. The fume passes through 

 the apparatus, and the electric discharge brings about 

 its precipitation. The mechanism of the process 

 appears to be somewhat obscure, and the account 

 given by Dr. Bush is very empirical. Further 

 scientific work will probably throw light on this 

 interesting process. Electrical precipitation has a 

 large field of possible applications. 



Separation of Isotopes of Mercury. — In the 

 January number of the Journal of the American 

 Chemical Society, Prof. W. D. Harkins and R. S. 

 Mulliken describe the experimental separation of 

 mercury into isotopic fractions by evaporation in a 

 vacuum. A difference in density of 133 parts in a 

 million was obtained. A theoretical discussion of 



the resolution of isotopic mixtures by diffusion and 

 similar processes is given, and equations are obtained 

 showing the rate of separation to be expected in 

 such processes. This work supplements previous 

 results by other workers given in Nature, voL^^cvi. 

 p. 144 ; vol. cviii. p. 209. 



Ammonia Oxidation. — During the war the oxida- 

 tion of ammonia was studied in England with a view 

 to its application in the State factory for the fixation 

 of nitrogen. Although the other parts of the chain 

 of operations leading from atmospheric nitrogen to 

 nitric acid never materialised, the process of ammonia 

 oxidation was brought to the stage of technical 

 application, and was taken up by different firms in 

 connection with the supply of oxides of nitrogen to 

 sulphuric acid chamber plants. In the Journal of 

 the Society of Chemical Industry for February 28, 

 Messrs. C. S. Imison and W. Russell, of the United 

 Alkali Company, give a very interesting and detailed 

 account of the improved process now in operation. 

 They remark that, so far as their experience goes, 

 there is little difference in cost between this and the 

 old retort processes for making strong nitric acid 

 with nitre and ammonia at present prices, but if the 

 published estimates for the cost of synthetic ammonia 

 are realised in this country, the balance will turn 

 strongly in favour of the oxidation process. They 

 also point out that the oxidation process is an integral 

 part of the process for the fixation of atmospheric 

 nitrogen, which, in conjunction with a fixation 

 process for ammonia, would render this country 

 independent of overseas supplies of nitre in the event 

 of another war. It seems strange that, among so 

 much legislation for " key industries," the absolutely 

 vital problem of nitrogen fixation has never been 

 mentioned. 



Radium Mining.— In a circular issued by the 

 Colorado School of Mines, entitled " A World Store- 

 house of Rare Metals, Radium, Uranium and Vana- 

 dium, the Paradox Field of South-western Colorado," 

 interesting information is given of the present con- 

 ditions prevailing in what is undoubtedly the richest 

 radium region of the world. The ore mined is 

 carnotite, a potassium uranyl vanadate of the 

 composition K20,2U03,V205,3H20, occurring in 

 sandstone in the San Miguel, Dolores, Mesa, and 

 Montrose counties of S.W. Colorado. The ore, as 

 mined, contains usually from 1-4 to i-8 per cent, of 

 uranium oxide, averaging some 4 milligrams of 

 radium to the ton and 4 or 5 per cent, of vanadium 

 oxide. Of a total of 52,000 tons produced in the 

 U.S.A., Colorado has produced 48,700 tons, of which 

 38,000 tons were mined by one company, the Standard 

 Chemical Co. of Pittsburgh. Smaller quantities have 

 been produced also in Wyoming and Utah. The 

 ore is prospected for by diamond drilling to a depth 

 of some 40 feet and mined by inclined shafts and 

 gravity tunnels. The deposits occur in sedimentary 

 rocks, and so far are confined practically to what is 

 known as the M'Elmo formation. Though easily 

 recognised as outcrops, the deposits of carnotite are 

 exceedingly variable and obey no law of deposition. 

 They are often associated with fossil wood as 

 " logs," in which the mineral has replaced the trunks 

 of trees embedded in the rocks. It is concentrated 

 in situ, if of less than 2 per cent. UgOg content, and 

 furnishes not only the largest present source of 

 radium but also an important source of the vanadium, 

 now so largely employed in the manufacture of 

 special steels. The Colorado School of Mines main- 

 tains a special well-equipped radioactivity laboratory 

 for the estimation and evaluation of these ores. 



NO. 2734, VOL. 109] 



