May i8, 1916] 



NATURE 



249 



paper there is an interesting account of the formation 

 and distribution of boulder and chalky flints; and in 

 the third the question of substituting other forms of 

 silica for flint in potter)-^ manufacture is discussed. A 

 timely article upon the national importance of fuel 

 economy is contributed by Prof. W. A. Bone. 



Several numbers of the Technologic Papers issued 

 by the United States Bureau of Standards have re- 

 cently come to hand. Each deals with a special 

 problem of analytical chemistry which has been in- 

 vestigated by the departmental chemists. In No. 64 a 

 new method is given for the determination of barium 

 carbonate in vulcanised-rubber articles, and it is 

 shown that the process is sufficiently accurate for use 

 in the somewhat difficult case where sulphates of lead 

 and barium are present simultaneously with the barium 

 carbonate. Paf>er No. 65 includes a scheme for the 

 determination of oil and resin in varnishes; tested 

 upon samples of known composition, the process has 

 given fairl}- good results. A method for the detection of 

 resin in driers is developed in No. 66. It appears to be 

 trustworthy except when the proportion of resin is very 

 small. Analytical chemists who may have to deal with 

 gums will find in paper No. 67 a useful summary of 

 the chemistry- of gum arable. The authors of the 

 paper find that basic lead acetate gives the most 

 characteristic reaction for this gum, whilst for its 

 quantitative determination they have devised an im- 

 proved process, depending upon the precipitation of 

 the gum with an alcoholic solution of copper acetate. 

 Paper No. 69 describes a critical study of the deter- 

 mination of carbon in steel by direct combustion in 

 oxvgen at temperatures higher than are ordinarily 

 eniploved. .Although the new method gives good 

 results, the investigators consider that the experimental 

 difficulties place it beyond the reach of most industrial 

 and works laboratories. 



The following works are in preparation for appear- 

 ance in Messrs. Longmans and Co.'s Monographs on 

 Biochemistry: — "The Development and Present Con- 

 dition of Biological Chemistry," Dr. F. Gowland Hop- 

 kins ; "'The Polvsaccharides," A. R. Ling; "Colloids," 

 W. B. Hardy ; '" Physical Methods used in Biological 

 Chemistry," Dr. G. S. Walpole; "Protamines and 

 Histones," Dr. A. Kossel ; "Lecithin and .\llied Sub- 

 stances," Dr. H. Maclean; "The Ornamental Plant 

 Pigments," A. G. Perkin ; "Chlorophyll and Haemo- 

 globin," H. J. Page; and "Organic Compounds of 

 Arsenic and Antimon;^" Dr. G. T. Morgan. 



Messrs. Macmillan and Co.'s list of forthcoming 

 books includes the following: — "A Bibliography of 

 British Ornithology, from the Earliest Times to the 

 End of 1912, including Biographical Accounts of the 

 Principal Writers and Bibliographies of their Pub- 

 lished Works," by W. H. Mullens and H. Kirke 

 Swann, in six parts, the first of which will be issued 

 at the beginning of June; "Discovery, or the Spirit 

 and Service of Science," by Prof. R. A. Gregory, illus- 

 trated (The purpose of the work is to display the 

 nobility of scientific endeavour, the meaning and value 

 of scientific method, and the practical service of results 

 obtained by research); "Theoretical Chemistry," by 

 Prof. W. Nernst, new edition, revised by H. T. 

 Tizard; "i\ Manual of Practical Physics," by H. E. 

 Hadlev; "Elements of Geometrv," by S. Barnard 

 and J.' M. Child, parts v. and vi. ; " Second Thoughts 

 of an Economist," bv the late Prof. W. Smart, with 

 a biographical sketch bv T. Jones; "The Military 

 Map : Elements of Modem Topography (French 

 School of War)"; "The Statesman's Year Book, 

 iqi6." edited by Dr. J. Scott Keltie, assisted by Dr. 

 M. Epstein. 



NO. 2429, VOL. 97] 



OUR ASTRONOMICAL COLUMN. 



Stereoscopic Spectroheuograms. — ^A remarkable 

 pair of photographs of hydrogen (H.) flocculi, show- 

 ing a stereoscopic effect, have been forwarded to us 

 by Prof. Hale. They were taken with a new grating 

 spectroheliograph, used in conjunction with the 60-ft. 

 tower telescope at Mt. Wilson, and exhibit the flocculi 

 surroundirsg a large spot-group near the sun's west 

 limb on August 7, 19 15. The time interval between 

 the two exposures was seven minutes, giving a separa- 

 tion of the two images due to the sun's rotation some- 

 I what greater than Helmholtz's estimate of i' for the 

 I minimum angular separation of two objects just 

 ; sufficing for stereoscopic vision. The photographs 

 ; show the structure of the flocculi in a way which at 

 ; once recalls Langley's well-known representation of 

 I the minute details of the photosphere about a spot; 

 ' and a long, dark flocculus, which afterwards ap- 

 peared as a prominence on the west limb, is dis- 

 I tinctly seen in relief. Photographs of this kind must 

 necessarily be affected by changes in the actual details 

 m the interval between the exposures, and by dis- 

 tortion arising from drift of the solar image, or 

 from irregular motion of the spectroheliograph, during 

 exposure; but Prof. Hale believes that with due pre- 

 cautions the stereograms will assist in clearing up 

 some of the questions referring to relative levels. A 

 check on the reality of the stereoscopic relief has been 

 obtained by taking photographs of a globe having a 

 roughened surface, turned through angles correspond- 

 ing with the intervals between the solar photographs. 



A Variation in the Solar Rotation. — In the pro- 

 gramme of spectroscopic work at the Ottawa Observa- 

 tory a considerable place is devoted to the investiga- 

 tion of the solar rotation. In the most recent publica- 

 tion Mr. H. H. Plaskett gives an account of a special 

 inquiry regarding its variability in time (Astrophysical 

 Journal, vol. xliii.. No. 2). In order to regularise the 

 personal equation and avoid bias all measurement was 

 postponed until the desired series of spectra had been 

 secured ; the plates were then mixed, divided into two 

 bundles, and measured with two quite (Afferent types 

 of machines. The displacements of eight lines, includ- 

 ing three of telluric origin, to serve as a check on 

 possible instrumental displacements, were measured. 

 Three possible modes of variation were looked for : (i) 

 diurnal ; (2) short period ; and (3) secular changes. The 

 evidence indicates that daily variations, if existent, do 

 not reach o-i km. ; Variations of the second and third 

 tvpes are revealed in a cyclic change of 0-15 km. with 

 a period of about a month, and a diminution of rota- 

 tional velocity amounting to 004 km. since 19 13- 

 The research is a typical example of the thoroughness 

 already traditional at Ottawa. 



The Great Meridian Circle of the Paris Observa- 

 tory. — The annual reports of the Paris Observatory 

 for the last two years contain some interesting facts 

 concerning the working of this instrument. After acci- 

 dental damages the indications of the repaired level 

 were discordant, so that throughout the past twelve 

 months the determinations of inclination of the axis 

 have been entirely made by nadir observations, employ- 

 ing the suspended mercur}' bath devised by M. Hamy. 

 Another modification of procedure concerns the col- 

 limation error. It was found that when the usual 

 daih' determinations were employed the resulting clock 

 rates showed variations greater than could be expected. 

 Consequently use is now made of a weighted mean 

 value of the colUmation error determined by observa- 

 tions of circumpolar stars at upper and lower culmina- 

 tions. 



