6^8 



NATURE 



[February 13, 1913 



they are rapidly becoming obsolete, and it is hoped 

 that shortly retroactive laws will make such contriv- 

 ances criminal. 



The tenth of the " Technologic Papers of the 

 Bureau of Standards " issued by the U.S. Department 

 of Commerce and Labour deals with the melting- 

 points of fire bricks, and is by Mr. C. W. Kanolt, 

 assistant physicist to the Bureau of Standards. Mr. 

 Kanolt has taken as the melting point the lowest 

 temperature at which a small piece of the brick could 

 be distinctly seen to flow. The experiments were 

 conducted in an Arsem graphite resistance vacuum 

 furnace, the temperatures being determined by means 

 of a Morse optical pyrometer of the Holborn-Kurl- 

 baum type, an improved method of calibrating, which 

 is described. The melting points of fifty-four samples 

 of fire brick, including fire clay, bauxite, silica, mag- 

 nesia, and chromite brick, have been determined. The 

 following melting points of materials important in the 

 manufacture of fire brick have been obtained by Mr. 

 Kanolt : — Kaolin, 1740° C. ; pure alumina, 2010° C. ; 

 pure silica, 1750° C. ; bauxite, 1820° C. ; bauxite clay, 

 1795° C. ; chromite, 2180° C. It is pointed out that 

 the value given for silica is not the true melting point, 

 but represents approximately the temperature at which 

 silica fiows distinctly. 



Further additions have been made by Messrs. 

 T. C. and E. C. Jack to their series of "People's 

 Books," which, it will be remembered, are sold at 

 6d. net each. Among the new volumes may be men- 

 tioned "Zoology, the Study of Animal Life," by Prof. 

 E. W. MacBride, which provides a popular introduc- 

 tion to the science, with chapters on such interesting 

 subjects as the origin of species, the consequences of 

 Darwin's theory, and the bearing of zoology on the 

 questions of human origin and the future destiny of 

 the rare. Dr. H. J. Watt's "Psychology" directs 

 attention mainly towards the study of experiences — 

 their analysis, description, classification, and connec- 

 tions. Mr. P. E. B. Jourdain, in "The Nature of 

 Mathematics," endeavours to make the ordinary per- 

 son understand " speaking broadly, what mathe- 

 maticians do, why they do it, and what, so far as we 

 know at present, mathematics is." In the volume on 

 ■ Friedrich Nietzsche," Mr. M. A. Miigge gives a 

 sympathetic account of the life of the philosopher. 

 Another volume takes the form of an atlas by Mr. 

 J Bartholomew, which contains fifty-six plates, and 

 is a marvel of cheapness. 



Messrs. Witherby and Co. are publishing photo- 

 graphic enlargements of six of the principal plates 

 from "The Home-life of a Golden Eagle," by Mr. 

 H. B. Macpherson, which contains some of the most 

 striking pictures of bird-life ever secured. The en- 

 largements measure gj by iii in., and that of "The 

 Mother Eagle and her Child," which has been sub- 

 mitted to us, is a most successful example of avian 

 portraiture. The price of each enlargement is -js. 6d. 



Messrs. J. and A. Churchill arc the publishers of 

 " Notes on Chemical Research," by Mr. W. P. 

 Dreaper, a notice of which appeared in last week's 

 Nature. Their name should have been given at the 

 head of the notice. 



NO. 2259, VOL. 90] 



OVR ASTRONOMICAL COLUMN. 



Latitude DibXRiBUTioN of Absorption Markings 

 ON Ha Spectroheliograms. — In an interesting note 

 appearing in No. 2, vol. Ixxiii., of The Monthly 

 Notices, Dr. Royds analyses the latitude distribution 

 of the dark absorption markings found on spectro- 

 heliograms taken in Ha light at the Kodaikanal Ob- 

 servatory during the period April, 1911-June, 1912. 

 Seventy-four per cent, of the total areas of absorption 

 markings occurred in the southern hemisphere, and 

 there was a slight preponderance in favour of the 

 western side of the central meridian. The latitude- 

 distribution curve for these markings agrees with that 

 for the limb prominences in showing a striking maxi- 

 mum near latitude 50° S., which is almost absent 

 from the corresponding northern latitude ; in the 

 northern hemisphere the maximum is in the zone 25° 

 to 30°. The association of Ha markings with sun- 

 spots is shown by the correspondence of their two 

 latitude curves between the equator and 20° N. and S. 

 It is suggested that maxima in the Ho curve in the 

 higher sun-spot latitudes may denote activity in those 

 regions presignifying the commencement of a new 

 sun-spot cycle. 



The Spectrum of the Corona. — The interdepend- 

 ence of physics and astrophysics is emphasised by an 

 article appearing in No. 458 of The Observatory, in 

 which Prof. J. W. Nicholson suggests that the spec- 

 trum of the corona may be given a physical inter- 

 pretation, based on the assumption that the 

 " coronium " atom is a simple one, in which the 

 actions of the component electrons may be theoretic- 

 ally determined. The majority of terrestrial atoms 

 are too complicated thus to be analysed, with our 

 present knowledge of mathematics, but among celes- 

 tial atoms Prof. Nicholson suggests there may be 

 some of sufficiently simple construction to enable the 

 mathematician to determine their structure, and so 

 deduce, from first principles, the nature of the spec- 

 trum emitted by them ; in " nebulium " and " coro- 

 nium " he believes such simple atomic structures are 

 to be found. 



If, according to theory, the model, simple atoin 

 consists of a number of negative electrons revolving 

 about a positive nucleus, it can be deduced that the 

 wave-lengths of the radiations emitted can have a 

 series of values of which the cube roots are in arith- 

 metical progression. Such series are found in the 

 spectrum of the corona, and the theory allows an 

 interpretation of nearly all the lines in this spectrum 

 to be set up. 



The Temperatures of Stars. — By comparing quan- 

 titatively the differences of intensity in various sections 

 of the spectrum. Dr. H. Rosenberg has educed tem- 

 peratures for seventy stars, and publishes his results 

 in No. 4628 of the Astronomische Nachrichten, where 

 he also describes his methods. The temperatures deter- 

 mined range from more than 400,000° C. for 7 Pegasi to 

 2150° for a Tauri, but the former is exceptional, the next 

 lower temperature being 50,000° for 7 Cassiopeiae. 

 The temperature of the sun, the intensity-difference 

 of the spectrum of which forms the basis of the 

 calculations, is, on this scale, 4950°. In the lower 

 temperatures Dr. Rosenberg's results agree fairly 

 well with those of Wilsing and Scheiner, but higher 

 up the scale the values are much greater. The 

 general concordance is shown when the intensity- 

 differences are plotted on a curve having for its 

 nbcissse the various spectral types of Miss Maury's 

 classification, the highest temperatures being exhibited 

 in both cases for the helium stars and those showing 

 bright hydrogen lines in their spectra. 



