5o6 



NATURE 



[August 17, 19 16 



American manufacture), each alleged to be chemically 

 pure, contained respectively 057, 0-45, and 049 per 

 cent, of potassium chloride. Samples prepared by 

 this author (i) by precipitation of a saturated solution 

 of common salt with hydrogen chloride ; (2) by purifica- 

 tion with milk of lime, excess of which was pre- 

 cipitated with sodium carbonate, the excess of the 

 latter being neutralised with hydrochloric acid; (3) 

 from metallic sodium by dissolution in water and 

 neutralisation of the solution with hydrochloric acid; 

 and (4) by neutralising with hydrochloric acid a solu- 

 tion of the most nearly pure caustic soda (not purified 

 with alcohol), contained respectively : (i) 0-42, (2) 0-32, 

 ^3) 0"27, and (4) 0-48 per cent, of potassium chloride. 

 In each case the potassium was estimated by the 

 platinic chloride method. It would be interesting to 

 Jearn whether the " chemically pure " sodium chloride 

 of English origin is equally contaminated. 



The ions of low mobility the presence of which in 

 air at ordinary pressures was discovered by Langevin 

 have frequently been called large ions owing to the 

 belief that their low mobility was due to their rela- 

 tively great mass. Some measurements rhade at the 

 suggestion of Prof. Millikan by Mr. L. B. Loeb, and 

 published in the July Proceedings of the American 

 Academy of Sciences, seem to indicate that this belief 

 was unjustified. Using the alternating-field method of 

 Rutherford, Mr. Loeb has measured the mobilities of 

 both positive and negative ions at fields from 90 to 

 i2,ooo volts per centimetre, and in neither case has 

 he found any marked increase in the mobility. At 

 the high speeds due to the strong fields the clusters of 

 uncharged molecules about an electron, which were 

 supposed to constitute the ion of low mobility, should 

 be broken up and the mobility show an increase corre- 

 sponding to the reduced mass. As the measurements 

 show no such increase, the author adopts the theory 

 that each ion consists of a single molecule and its low- 

 mobility is due to the action of its charge on neutral 

 molecules increasing the number of collisions. 



.\ccoRDiNG to the Scientific American, there has been 

 a remarkable increase, since the war commenced, in 

 the number of American engineering firms who make 

 use of the metric system of measurement. Many firms 

 who t\yo years ago upheld the yard, foot, inch, eighths, 

 sixteenths, thirty-secondths, and sixty-fourths as more 

 convenient than the metre and its decimal sub- 

 divisions are now turning out machines gauged 

 solely on the metric system. This remarkable volte- 

 face appears due to the desire on the part of American 

 firms to meet the demand for machinery which, in 

 the past, has been supplied by Germany. Whatever 

 the reason for this rapid change, the fact that it has 

 been carried out voluntarily in so short a time seems 

 a sufficient refutation of the argument that the intro- 

 duction of the metric system into engineering works 

 in this country would cause endless confusion and 

 great expense. 



We have received from Prof. R. Gautier, director of 

 the Geneva Observatory, the annual report describing 

 the chronometrical service carried on in that institu- 

 tion. It appears from the report that the war has 

 affected the activity of the observatory very adversely, 

 and that the number of instruments submitted to trial 

 conditions has fallen below that of any year since 

 1872. Of marine chronometers only one has been 

 received, and of pocket watches, 152, as against 296 

 in 1914. M. Gautier takes, however, a hopeful view 

 of the national industry in the future when normal 

 conditions have returned, basing this opinion on the 

 improved character of the work. For if the number 

 of instruments has been less, the proportion of those 



NO. 2442, VOL. 97] 



which obtain the highest certificate of excellence has 

 increased. No less than 95 per cent, of the whole 

 deposits has obtained a first-class certificate, and less 

 than 10 per cent, of the instruments submitted to test 

 has failed. These figures constitute a record in the 

 history of the annual trials. M. Gautier gives some 

 details of the examination of chronometers at the 

 neighbouring observatories of Neuchatel and Besan- 

 9on, giving also an abstract of the Kew results for 

 comparison. The effect of the war is everywhere 

 noticeable in the quantity of instruments deposited, 

 but the quality oT the work is everywhere maintained 

 with gratifying uniformity. The general adoption of 

 the Guillaume balance has contributed to this success- 

 ful result. In the Kew report it is stated that the 

 Swiss manufacturers have universally adopted the 

 Guillaume t\'pe, and "il n'y a pas de doute que 

 I'emploi de ce type de balancier contribue largement 

 aux brillants r^sultats obtenus par les montres 

 d^pos^es par ces fabricants." 



In response to many requests, the Board of Agri- 

 culture and Fisheries has issued (at 15.) a second 

 edition of vol. i. of the " Special Reports on the 

 Mineral Resources of Great Britain." It will be 

 remembered that the work deals with the uses, dis- 

 tribution, treatment, and output of tungsten and 

 manganese ores, and that in it particulars are given 

 of the mines containing the ores. 



An interesting volume has been sent to us by the 

 Royal Cornwall Polytechnic Society, entitled " His- 

 torical Synopsis of the Royal Cornwall Polytechnic 

 Society for 81 Years, 1833-1913," by Wilson Lloyd 

 Fox, with indexes by Howard Fox. The work 

 is divided into two parts, covering the periods 

 1833-81 and 1882-1913. The activities of the society 

 have been numerous and valuable, and merit this 

 permanent record. 



A NEW series entitled the " Cambridge Botanical 

 Handbooks " is being edited by Prof. A. C. Seward 

 and Mr. A. G. Tansley for the Cambridge University 

 Press. The development of certain branches of 

 botanical science in recent years has emphasised the 

 need for books by specialists on different groups of 

 the vegetable kingdom, and the new series is being 

 issued to meet this want. A book by Prof. West 

 dealing biologically with all the algas included in the 

 Myxophyceas, Peridinieae, Bacillacieae, and Chloro- 

 phyceae, both fresh-water and marine, will be the first 

 volume to appear. It will be followed by another 

 work by Prof. West, on all the fresh-water algae 

 (with the exception of desmids and diatoms) which 

 are known to occur in the British Isles. Volumes on 

 lichens, fungi, and gnetales, by Miss Lorrain Smith, 

 Dr. Helen Gwynne-Vaughan, and Prof. Pearson 

 respectively, are in an advanced state of preparation. 



The Harvard University Press (Cambridge, Mass., 

 U.S.A.) has begun the publication of a series entitled 

 "Harvard Health Talks," being the substance of some 

 of the public lectures delivered at the Medical School of 

 Harvard University, and aiming at providing in easily 

 accessible form modern and authoritative information 

 on medical subjects of general importance. Among^ 

 the volumes in the series we notice "The Care an4H 

 Feeding of Children," by J. L. Morse; "Preservatives" 

 and other Chemicals in Food : their Use and Abuse," 

 bv O. Folin; "The Care of the Skin," by C. J. White; 

 "'The Care of the Sick Room," by E. G. Cutler; and 

 "The Care of the Teeth," by C. A. Brackett. The 

 series is published in this country by the Oxford Uni- 

 versity Press. 



