April 8, 1909] 



NATURE 



169 



appeared to show the existence of double molecules; 

 potassium chloride was normal, and sodium, silver, barium, 

 and strontium nitrates were nearly normal, showing a 

 slight dissociation. Sodium chloride behaved as though 

 dissociated into two, barium and strontium chlorides into 

 three parts, whilst the figures for potassium and sodium 

 sulphates were quite abnormal, being split up into more 

 than three parts. 



Is response to a widely expressed request, Dr. H. O. 

 Forbes, director of museums and reader in ethnography 

 in the University of Liverpool, has agreed to publish, in 

 book form, the course of lectures recently delivered by 

 him in the Museums Theatre, on " The Reindeer 

 Hunters : the Golden Age of the Cave-dwellers." The 

 volume will be issued in the autumn. 



We have received a copy of the list of publications 

 already issued by the Carnegie Institution of Washington. 

 The list includes particulars of iiS monographs and other 

 works, many of which have been reviewed in Nature 

 from time to time, and it provides further evidence of 

 the excellent work which the institution is accomplishing 

 in disseminating a knowledge of recent progress in science. 

 The editions of each book are restricted, and as soon as 

 a volume is issued copies of it are sent gratuitously to a 

 limited number of the greater libraries of the world, while 

 the remainder of the edition is placed on sale at a price 

 sufficient only to cover the cost of publication and of 

 carriage to purchasers. 



A NEW and revised edition of Prof. W. Bolsche's book, 

 " Haeckel : his Life and Work," has been published by 

 Messrs. Watts and Co. for the Rationalist Press Associa- 

 tion, Ltd. The book is published at the price of 6d., and 

 is provided with an introduction and supplementary 

 chapter by the translator, Mr. Joseph McCabe. 



Messrs. Cassell and Co., Ltd., have commenced the 

 issue, in fortnightly parts, of Prof. Percy Groom's beauti- 

 fully illustrated "Trees and their Life-histories." The 

 price of each part is \s. net, and there will be thirteen 

 of them to complete the work. The same firm is issuing 

 Prof. F. E. Hulme's " Familiar Wild Flowers " in fort- 

 nightly parts at bd. net each, and there will be forty- 

 five parts. 



.■\ FOURTEENTH edition of Mr. W. T. Lynn's " Remark- 

 able Com.ets " has been published by Messrs. Samuel 

 Bagster and Sons, Ltd. In this issue, particularly, the 

 author has endeavoured to bring the information carefully 

 up to date. The price of the little book is 6d. net. 



OUR ASTRONOMICAL COLUMN. 



Positions of Daniel's (igoyd) and Morehouse's (igoSc) 

 Comets. — Comet 1907^ having been observed during the 

 opposition of igo8, Herr H. H. Kritzinger has calculated 

 an ephemeris for the coming opposition, and publishes it 

 in No. 4317 of the Astronomische Nachrichten. The 

 ephemeris position for April 16 is I5h. 20-2m., —7° 50', 

 and the estimated magnitude is 14-3, but the comet may 

 be as much as 38 magnitudes fainter than this. There 

 is just a possibility, however, that it may be re-observed 

 by long-exposure photographs. 



An ephemeris for comet igoSc, prepared by Dr. Ebell, 

 appears in No. 4309 of the Aslroiiomischc Nachrichten, and 

 gives the positions and estimated magnitudes of the comet 

 up to the end of June. From this we see that the comet 

 will not rise in these latitudes until about the end of May, 



and will then be only about one-third as bright as it was 

 when discovered. 



SuN-sroTS AND SoLAR TEMPERATURE. — In the March 

 number of the Observatory Mr. Evershed continues the 

 discussion as to the interpretation of the phenomena of 

 the sun-spot spectrum with regard to temperature. In 

 a previous letter Prof. Whittaker suggested that the tube- 

 furnace phenomena observed by Dr. King might be pro- 

 duced by the direct action of the radiation absorbed from 

 the heated walls of the solid tube rather than in con- 

 sequence of the collisions between the molecules of the 

 gases themselves. This suggestion Mr. Evershed believes 

 to be unnecessary for the explanation of the radiations 

 observed, and he adduces evidence showing that the mole- 

 cules of the gases, when excited thermally, are capable, 

 by their mutual collisions at high velocities, of producing 

 the radiations. 



In regard to Prof. Whittaker's second suggestion, that 

 the increased intensity of spot lines may be due to 

 enormous pressures obtaining in the lower parts of the 

 chromosphere, Mr. Evershed quotes experimental results 

 showing that such pressures are unnecessary for the pro- 

 duction of the intensifications, and then shows that the 

 evidence for the existence of the pressure-differences_ re- 

 quired by this hypothesis is insufficient. He mentions, 

 parenthetically, that he has observed what appears to be 

 a minute pressure effect on certain lines measured at the 

 sun's limb, and suggests that further observations of this 

 phenomenon may lead to conclusions regarding the various 

 levels at which absorption takes place. 



The Apparent Dispersion of Light in Space. — In arr 

 article appearing in the March number of the Astro- 

 physical Journal (vol. xxix.. No. 2, p. loi) Prof. Lebedew 

 criticises the conclusions arrived at by Belopolsky, Nord- 

 mann, and Tikhoff concerning the dispersion of light irh 

 interstellar space. 



In the first place, he shows that if the delay found by 

 Tikhoff and Nordmann were due to ponderable matter, the- 

 absorption produced by such matter would be so great as 

 to render the sun and stars invisible to us. There re- 

 mains the possibility that the a;ther itself disperses, with- 

 out absorbing; light, but this entails an attack on the 

 electromagnetic theories of light, which Prof. Lebedew 

 believes to have been too firmly established, by theory and 

 experiment, to allow of any attack being made simply to 

 explain a series of astronomical observations. 



Prof. Lebedew then shows that Tikhoff's assumptions 

 are unsafe, and that his results do not agree sufficiently 

 closely with those of Nordmann to produce conviction, 

 and, finallv, he shows that in the case of such systems 

 as those of /3 AurigiE and R.T. Persei physical processes 

 sufficient to produce the phenomena observed may be- 

 readily conceived. 



Coloured Stars in the Globular Cluster M 13. — In. 

 the October number of the Astrophysical Journal for 1900- 

 Prof. Barnard directed attention to some " abnormal "■ 

 stars observed by him in the globular cluster M 13. 

 Herculis, such stars being relatively much fainter visually 

 than photographically. 



Since the publication of this result he has found other 

 stars of this class in the same cluster, and also in- 

 .M 5 Librae. On comparing a photograph of the cluster 

 taken with the Potsdam refractor with one taken with 

 the Yerkes 40-inch refractor fitted with a yellow screen, he 

 was surprised to find that there were many more of these 

 "blue" stars than he had hitherto found; further, a 

 , large number of the stars of this cluster must be yellow, 

 for they are relatively much brighter on the Yerkes than 

 on the Potsdam photograph. 



Thus, while it is impossible visually to observe anvi 

 difference in the colours of the stars of M 13, the above 

 comparison shows that great differences of colour, and 

 hence of spectral type, do exist, and Prof. Barnard now 

 gives t.ables showing which are the blue and which are 

 the yellow stars ; he also mentions one or two striking 

 examples of colour-difference, and briefly discusses tho 

 variable stars hitherto discovered in this cluster (.45fr£>- 

 physical Journal, vol. xxix., No. i, p. 72). 



NO. 2058, VOL. 80] 



