August 5, 1920] 



NATURE 



725 



a favourable condition, but this year pressure is in 

 slight defect. It is stated that the conditions indicate 

 that in North-West India the monsoon is likely to be 

 weak, at any rate in the earlier part of the season, 

 and for the rainfall of the Peninsula, North-East 

 India, and Burma the indications are not sufficiently 

 '•finite to justify a forecast. 



The Italian Laboratory of Practical Optics and 

 Mechanics of Precision, which was founded in 

 Florence last year on the suggestion of the Minister 

 of Public Instruction to spread a knowledge of recent 

 advances in instrument-making amongst those engaged 

 in the industry in the country, has undertaken the 

 issue of a monthly Review of Optics and Mechanics 

 of Precision. The number for March and April con- 

 sists of a little more than thirty quarto pages. The 

 first seven are devoted to a continuation of a report 

 by Prof. L. Silberstein on the quantum theory of 

 spectra. The improvements which Sommerfeld has 

 introduced into the theory by ascribing two degrees 

 of freedom to the electron instead of the one degree 

 of Bohr's theory are dealt with. Constructional optics 

 is represented by articles on the calculation of 

 achromatic objectives and on objectives for aerial 

 photography. Metrology gets an article of sixteen 

 pages on measurements of precision in the mechanics 

 workshop by Mr. V. I. N. Williams, of Armstrong, 

 Whitworth's, Manchester. There appears to be no 

 publication in English which serves the same purpose 

 for our own industries that this review does for those 

 of Italy. 



The July issue of Science Progress contains a 

 , stand by Mr. S. C. Bradford of the theory of the 

 constitution of the atom propounded by Langmuir 

 in the June issue of the Journal of the American 

 Chemical Society last year. Unlike the "sun and 

 planets " theory which has been so successfully 

 developed by Bohr, the new theory assumes the elec- 

 ' trons which surround the positive nucleus to be at 

 rest. They form shells around the nucleus, the 

 number in each shell being twice the square of the 

 number of the shell counted from the nucleus. When 

 the number of electrons is insufficient to fill a number 

 of shells, it is the outer shell which is incomplete. In 

 these outer shells there is a tendency for the electrons 

 to form groups of eight or "octets " either amongst 

 themselves or by association with the electrons of 

 other atoms. The chemical properties of the atom 

 depend mainly on the number of electrons in the 

 outer shell not associated together in octets. The 

 properties of hydrogen, helium, neon, lithium, carbon, 

 nitrogen, oxygen, and fluorine, the similarity in the 

 Ix'haviour of CO,, and N,0, of CO and N,, and the 

 difficulties which compounds of nitrogen raise on the 

 usual theory of valency, are all e.xplained in a simple 

 w ay by the new theory. 



In Nature of July 8 we gave an account of the 

 work done recently at the National Physical Labora- 

 tory. The appearance of the report of the laboratory 

 for the year iqig enables us to supplement that 

 account by some information as to the progress of 

 the institution as a Government establishment. With 

 "< rfard to buildings, the new control appears to J 

 NO. 2649, VOL. 105] 



involve exceptional delay. Extensions contemplated in 

 19 18 and urgently needed have been approved by 

 the Research Department, but not yet authorised 

 by the Treasury. In consequence, apparatus already 

 delivered cannot be housed and utilised. The number 

 of posts in each grade of staff has been fixed, and the 

 conditions of service approximate to those in the Civil 

 Service. In special cases, however, promotion by 

 length of service may be departed from, subject to 

 the approval of the Research Department. Industry 

 appears to be claiming many of the staff who have 

 by their past work added materially to the reputation 

 j of the Laboratory, and it is of the utmost importance 

 that the most promising of the younger members of 

 the staff should be retained by sufficiently attractive 

 posts. The Research Department has decided that 

 commercial testing is not in future to be a function 

 of the Laboratory. 



A report by Prof. J. C. McLennan on sources of 

 helium in the British Empire has recently been issued 

 by the Department of Mines, Canada (Bulletin No. 31). 

 An investigation of the helium content of natural gas 

 supplies was undertaken at the request of the Board 

 of Invention and Research (London) in 1915, and the 

 report embodies the results, which are now published 

 by permission of the Admiralty. It appears that 

 certain natural gases in Canada form the largest 

 source of supply of helium at present known within 

 the Empire. The percentage of helium present was 

 found to range from zero in gases from the Toronto 

 and British Columbia regions up to about 033 per 

 cent, in gases from the Blackheath (Ontario) and 

 Bow Island (Alberta) areas. Two methods were used 

 for isolating the helium : (i) Combustion of the gas 

 vi^ith oxygen, the resulting water and carbon dioxide 

 being removed by suitable reagents, and the nitrogen 

 and remaining traces of other gases by means of coco- 

 nut charcoal cooled in liquid air; and (2) condensa- 

 tion of the hydrocarbons and other constituents having 

 higher boiling points than helium in a condenser im- 

 mersed in liquid air, the residue being then purified 

 by means of charcoal as before. Figures of the 

 apparatus employed are given. Methods based upon 

 these processes are indicated for the large-scale manu- 

 facture of helium, and it is considered that com- 

 mercial production of the gas is almost certain to be 

 undertaken. 



From the Central Scientific Co., Chicago, we have 

 received a copy of its catalogue of apparatus used in 

 chemical, bacteriological, biological, industrial, and 

 soil-testing laboratories. The catalogue is very com- 

 plete, and it indicates the thorough manner in which 

 American manufacturers have developed the produc- 

 tion of scientific apparatus. Practically all the articles 

 described are stated to be "American made," the onlv 

 important item of foreign manufacture being English 

 (Whatman) filter-paper. Among other matters of 

 interest we note the new "chain" analytical balance, 

 in which the use of a rider and small weights is 

 dispensed with. The finer weighings are obtained by 

 varying the length of a small gold chain attached at 

 one end to the beam of the balance, and at the other 

 to a vernier which slides on a graduated vertical 



