November 7, 1912] 



NATURE 



287 



of the editor of that journal, Dr. L. A. Bauer. The 

 subject has been recently dealt with by Prof. Schuster 

 in his address to the Physical Society of London, and 

 ty Dr. W. F. Swann in the July number of The 

 Philosophical Magazine. The conclusion to which 

 each examination leads is that none of the present 

 theories offers a satisfactory explanation of the earth's 

 magnetic state. In the September number of Terres- 

 trial Magnetism Dr. Bauer shows that if the mean 

 values of the magnetic elements be calculated for suc- 

 ■cessive parallels of latitude between 60° N. and 60° S., 

 these values are represented to within i per cent, by 

 an e.xpression for the magnetic potential which in- 

 volves only the first and third zonal harmonics; that 

 IS, it involves the first and third powers only of the 

 ■cosine of the colatitude. This fact serves as a very 

 severe test of any theory advanced, and none of them 

 -appears capable of surviving its application. 



An interesting paper on the occurrence, analysis, 

 and genesis of iridosmine obtained from the New 

 Rietfontein Mines is communicated by Mr. C. Baring 

 Horwood to vol. xv. of the Transactions of the Geo- 

 logical Society of South Africa. Iridosmine is an 

 intimate mixture of iridium and osmium, found in 

 small quantities, as small grey particles, associated 

 with gold. Specimens microscopically examined by 

 the author showed a decidedly crystalline character, 

 but the metal has never been recognised in situ or in 

 hand specimens; "panning" experiments show that in 

 the New Rietfontein it chiefly occurs in a very narrow 

 banket reef, known as the carbon leader, wherein the 

 gold is always associated with carbon. Spectroscopic 

 analyses, made for Mr. Horwood at the Solar Physics 

 Observatory, South Kensington, indicate that the 

 iridosmine is mainly composed of osmium, ruthenium, 

 and iridium. A concentrate examined quantitatively 

 at the Imperial Institute had a specific gravity of 19, 

 and contained 95 per cent, iridosmine, of which 45 per 

 cent, was iridium. The metal does not occur in pay- 

 ing quantities, and it took six months to collect 910 

 grains at the Rietfontein Mine, during which period 

 102,800 tons of ore were treated, and more than 52,500 oz. 

 of fine gold were recovered. Mr. Horwood concludes 

 that these metals of the platinum group are certainly 

 of secondary origin, formed as primary segregations 

 by magmatic concentration in the basic eruptives of 

 the mines, and extracted from the dykes by active 

 superheated gases during the pneumatolytic phase of 

 eruptive activity. Probably, at a later stage, hydro- 

 thermal action was an important factor in concentrat- 

 ing them in the banket reefs. 



. -ArxENTiON may be directed to an article on 

 isomerism by Werner Mecklenburg in Naturwissen- 

 schaftliche Wochenschrift for October 20. The 

 article, which extends over ten pages, and occupies 

 the larger part of the issue, deals with the pheno- 

 mena of position isomerism, optical isomerism, 

 stereo-isomerism, and dynamic isomerism, together 

 with the Walden inversion and the isomeric deriva- 

 tives of cobalt and other metals as investigated by 

 Werner. 



We have received from Messrs. A. Hermann et Fils 

 a reprint of a series of lectures " Sur qiielques Thames 

 NO. 2245, VOL. 90] 



choisis de la Chimie Physique pure et appliqu^e," de- 

 livered by Prof. Arrhenius at the University of Paris 

 from March 6 to 13, 191 1. Some of the subjects 

 are identical with those of the Silliman lectures de- 

 livered at Yale in 191 1 and published recently under 

 the title "Theories of Solution"; this statement 

 applies to the lectures on molecular theory, on sus- 

 pension and the phenomena of adsorption, and on free 

 energy. But different ground is covered by the lec- 

 tures on the atmospheres ot planets and the physical 

 conditions of the planet Mars. The five lectures cover 

 112 pages, and are issued at the modest price of 

 three francs. 



The yearly memorandum issued by Mr. C. E. 

 Stromeyer, chief engineer of the Manchester Steam 

 Users' Association, deals with the relative costs of 

 burning fuel or oil under boilers, and exploding oil 

 or gas in engines. With the ruling prices of oil, it 

 will not be profitable to burn it in preference to coal 

 until the price of the latter has risen to 38s. per ton ; 

 but oil can be profitably used in internal-combustion 

 engines whenever and wherever the price of coal ex- 

 ceeds 155. per ton. The greater part of the memor- 

 andum deals with the valuable experiments of Profs. 

 Heyn and Bauer on corrosion, or rather on the influ- 

 ence of about forty dissolved salts in reducing or 

 increasing corrosion. The phenomena associated with 

 corrosion are too erratic to permit of definite conclu- 

 sions being drawn, but Mr. Stromeyer gives an excel- 

 lent analysis of the experiments mentioned which will 

 be of great service to steam users who are troubled 

 with corrosive feed waters. 



We have before us twenty-two volumes belonging 

 to the series "Aus Natur und Geisteswelt," published 

 by the firm of Mr. B. G. Teubner, of Leipzig and 

 Berlin. The series now includes nearly four hundred 

 volumes dealing with many aspects of literature, art, 

 music, history, law, philosophy, science, and tech- 

 nology. The price of each volume is one mark, or 

 1.25 marks in cloth covers. A distinguishing character- 

 istic of the series is the attention given to present-day 

 problems. Among the subjects of recent volumes, for 

 instance, are directions of modern physics, experi- 

 mental cytology, regeneration, biochemistry, milk and 

 its products, problems of modern astronomy, astronomy 

 in relation to practical life, surgery of our time, prac- 

 tical mathematics, spinning, light-railways, wireless 

 telegraphy, aerial navigation, brewing, and kinemato- 

 graphy. Each volume is simply written and suitably 

 illustrated, and the whole series forms a remarkably 

 comprehensive collection of manuals of modern 

 thought and progress. Both the editor and publisher 

 are to be congratulated upon the production of the 

 volumes, which should do much to promote interest 

 in science, art, and letters among German readers. 



A NEW issue of the list of second-hand microscopes 

 and other instruments which they have on sale has 

 been issued by Messrs. Clarke and Page, 23 Thavies 

 Inn, Holborn Circus, London, E.G. 



A CATALOGUE of works on anthropology, ethnology, 

 primitive society, &c., also mythology and folk-lore, 

 including a portion of the library of Sir H. H. Risley, 



