September 29, 1923] 



NA TURE 



48: 



to those instruments, and to early descriptions of 

 instruments, by which scientific studies in the uni- 

 versity have been advanced. 



Dr. D. H. Scott is bringing out through Messrs. 

 ]\lacmillan and Co., Ltd., " Extinct Plants and 

 Problems of Evolution," a volume founded on a 

 special course of lectures given in 1922 at the Uni- 

 versity "College of Wales, Aber>'stwyth, the object 

 being to sketch, in broad outline, the geological 

 history of the plant-kingdom, in its bearing on the 

 theory of descent. Messrs. Macmillan also announce 

 " Life in Southern Nigeria : The Magic, Beliefs, and 

 Customs of the Ibibio Tribe," by Amaury Talbot, 



Resident, Nigeria ; vol. iii. (Mammalia) of Prof, 

 von Zittel's " Text-book of Palaeontology," revised 

 by Dr. Max Schlosser, translated under the direction 

 of the late Dr. C. R. Eastman, by Marguerite L. 

 Engler and Lucy P. Bush, and revised by Dr. A. 

 Smith Woodward ; and a new and revised edition of 

 Prof. W. J. Sollas's " Ancient Hunters." 



Errata : — In the article on " The Earth's Magnetic 

 Field for 1922," by Dr. Louis A. Bauer, in our issue 

 of August 25, the formula on p. 295 should be given 

 the number (i) ; the second author mentioned in the 

 fourth paragraph, third line, p. 296, should be Mr. 

 H. Furner instead of Prof. H. H. Turner. 



Our Astronomical Column. 



The Solar Eclipse of 1922 and Einstein's 

 Theory. — The current number of the Lick Observa- 

 tory Bulletin, No. 346, contains the results of the 

 observations on the deflexion of light in passing 

 through the sun's gravitational field made during the 

 total solar eclipse of September 21, 1922, at Wallal, 

 Western Australia. The authors, Prof. W. W. 

 Campbell and Mr. R. Trumpler, give all details for 

 this particular research, which represents only a part 

 of the programme of the William H. Crocker Eclipse 

 Expedition from the Lick Observatory. Two very 

 interesting diagrams show at a glance the type of the 

 results obtained. The first of these is a star chart of 

 the neighbourhood of the eclipsed sun containing 

 the 92 stars actually measured for the investigation. 

 The observed relative displacements of the stars are 

 indicated by short lines oriented according to the 

 directions of displacements. The outline of the 

 brighter parts of the corona as well as the limit of the 

 faintest traces of coronal light are indicated. The 

 second instructive diagram shows the observed radial 

 displacements for each star as a function of the star's 

 angular distance from the sun's centre, while for 

 comparison sake a curve is given indicating the 

 values predicted by Einstein's theory. This graphical 

 representation demonstrates the coincidence between 

 the observed and the predicted light deflexions. By 

 arranging the stars in groups according to their 

 distance from the sun's centre the observed relative 

 radial displacements can be seen from the accom- 

 panying table. 



It will be noted that the observed radial displacements 

 given in this table are in remarkably good agreement 

 with the values predicted on the basis of Einstein's 

 theory. The authors point out also that even the 

 stars between 1-25° and 2-25° from the sun's centre, 

 which lie entirely outside of any trace of the corona, 



NO. 2813, VOL. 112] 



show the light deflexion well marked, an effect that 

 would be difficult to explain by an extended solar 

 atmosphere. 



Ephemerides of Algol Variable Stars. — At the 

 meeting in Rome of the International Astronomical 

 Union in 1922, the representatives of the Cracow 

 Observatory undertook the calculation and publica- 

 tion of these ephemerides. No. i, containing these 

 calculations for the second half of 1923, has lately 

 come to hand, edited by Th. Banachiewicz. The 

 explanatory matter is printed both in Polish and in 

 Peano's flexionless Latin, the latter being easy to 

 read. 



Comment is made on the fact that from the date 

 January i, 1925, the astronomical day will begin at 

 midnight, which will cause a break of continuity in 

 formulae that use the Julian day (beginning at noon). 

 To avoid confusion, it is suggested that a new cycle 

 of days be employed for this purpose, the zero date 

 being the midnight at the beginning of January o, 

 1 80 1 (Greenwich). This is adopted in the present 

 work, and tables are given to reduce calendar dates 

 to it. Tables are given for 31 stars, including Algol, 

 the adopted elements being corrected by recent 

 observations, made in several cases by J. Gadomski at 

 Cracow. The times of minimum are given to the 

 third decimal of a day (about i^ minute). 



Since all the minima occurring on each day are 

 arranged on the same page and in the same line, it 

 is a very simple matter to draw up a programme of 

 work on any given night. 



Further Search for Intra-Mercurial Planets. 

 — Though we know from the presence of the Zodiacal 

 Light that there is a considerable amount of scattered 

 matter inside the orbit of Mercury, it becomes more 

 and more unlikely with each total eclipse that there 

 is any single body of sufficient size to be separately 

 discerned or photographed. Prof. Campbell and Mr. 

 Trumpler have made a careful search on the large 

 plates (17 inches square) taken for the Einstein prob- 

 lem in the eclipse of September 1922. They embrace 

 an area of 15° x 15°, and show 550 stars, the faintest 

 being of magnitude 10-2. They were compared, star 

 by star, with the comparison plates taken in "Tahiti 

 four months earlier. Nothing was detected in the 

 search ; it is noted that rapid motion might weaken 

 a planet's image, but, allowing for this, there could 

 not have been any planet as bright as magnitude 8-5 

 in the region of the plates, unless it was in the denser 

 parts of the corona. Perrine's search in 1908 covered 

 a region 25° x 8J°, but did not reach quite such faint 

 stars as the present series. 



