October 8, 1908J 



A^A TURE 



569 



Part ii. deals with actual weather conditions, 

 with cold and warm waves, and types of 

 weather, illustrated by beautifully executed synchron- 

 ous charts. The discussions, which will be of the 

 utmost interest to the students of practical meteor- 

 ology, direct especial attention to the relation between 

 wind-direction and temperature, the distribution of 

 clouds, rainfall, &c. The author makes use of the 

 long- series of data at his disposal to test several 

 points of popular interest. The temperature observa- 

 tions, extending- over a period of eig-hty-seven years, 

 do not exhibit any tendency to the cold period about 

 May 10-13 which is observed in Europe; on the 

 contrary, there is a distinct rise, probably due to high 

 barometric pressure at this time over the southern 

 Atlantic States. Nor do they show any regular re- 

 currence of cold and warm periods ; the only negative 

 conclusion that the author considers may be safely 

 drawn is that a cold winter is not likely to be fol- 

 lowed by a.warm spring- or summer, and that a warm 

 winter is not likely to be followed by a cold spring 

 or summer. The observations clearly disprove the 

 popular belief in the occurrence of severe storms at 

 the equinoctial periods of March and September, while 

 a comparison of weather conditions with the sun- 

 spot curves neither proves nor disproves any intimate 

 relation. We congratulate the author on the able 

 way in which he has dealt with the whole subject, 

 without having had recourse to mathematical 

 formulae. 



A Monograph of the Silurian and Devonian Corals 

 of Neiv SoiitJt Wales. Part ii. By R. Etheridge, 

 jun. (.Sydney, 1907.) 



This part deals with the g-enus Tryplasma, of which 

 several new species are described, from the Upper 

 Silurian of the neighbourhood of Yass. A historv of 

 the genus is given, together with an account of its 

 relations to other g-enera and its systematic position. 

 Attention is directed to the intimate relation existing 

 between the structure of Lindstrom's Pholidophylhim 

 and that of Tryplasma, but in none of the .Australian 

 .species of the latter have been found any of the 

 exothecal scales which led Lindstrom to consider 

 Pholidophylhim iuhulaium (Schloth.) homologous in 

 a certain sense with Calceola, Goniophylluni, and 

 Rhizophyllum. The author advocates the removal of 

 Ph. tubidatutn, as a representative Tryplasma, from 

 the vicinity of the Antho::,oa operculata to a separate 

 family, the Trvplasmidse, with relations to Amplexus 

 and Pycnostylus. The general structure of the 

 Australian Tryplasmidre is described in detail, but the 

 examination of the development of the septal lamella 

 and spines by means of serial sections was not 

 attempted. 



The Fauna of British India, inchtding Ceylon and 

 Burma. Published under the authority of the 

 Secretary of State for India in Council. Edited 

 by Lt.-Col. C. T. Bingham. Rhynchota. Vol. iv., 

 part ii. Homoptera and .Appendix (Part i.) By 

 \V. L. Distant. (London : Taylor and Francis, 

 1908.) Price 10s. 



\\'e congratulate the editor and author on the appear- 

 ance of another half-volume of this important work. 

 The present instalment is devoted to the homopterous 

 family Jassidas, subfam. v. Jassinae (including 

 Acocephalince), comprising twelve divisions, and 

 subfam. Typhlocybina?, with two divisions. The 

 species included are numbered from 2509 to 2696. An 

 appendix is commenced, including additions to the 

 Rhynchota Heteroptera discussed in vol. i. ; and the 

 portion now published relates to the families Penta- 

 tomidae, Coreid<E, and Berytida, and the additional 



NO. 2032, VOL. 78] 



species are numbered from 2697 to 2768. The general 

 character of " The Fauna of British India " is so well 

 known, and has been so frequently commented on, 

 that it is only necessary to say that the present half- 

 volume is similar to those which have preceded it, 

 and that the high character of the series is fully 

 maintained. 



How li'e Travel. A Geographical Reader. ByJ.F. 

 Chamberlain. Pp. ix + 227. (New York: The 

 Macmillan Co., 190S.) Price 2s. 6d. 



The intention of the author of the series of four 

 reading books, of which this is the last, is to develop 

 an interest in the subject on the part of young pupils 

 beginning the study of geography. The little book 

 should be popular in the lower classes of secondary 

 schools; it provides a simple, entertaining, and 

 attractively illustrated account of means of travel and 

 communication in various parts of the world. Pre- 

 vious volumes have dealt w-ith man's activities con- 

 nected with securing food, clothing, and shelter. 



LETTERS TO THE EDITOR. 



[The Editor does not liold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the zuriters of, rejected 

 manuscripts intended for tliis or any other part 0/ Nature. 

 No notice is talien of a)iony}}WUs conmntnications.] 



Solar Vortices ar.d Magnetic Fields. 



Several weeks ago I discussed with Prof. Hale the 

 matter of solar vortices and magnetic fields, with refer- 

 ence to his recent discoveries, briefly described in Nature 

 for August 20 (p. 368). It did not seem to me probable 

 that the effects could be accounted for by unequal diffu- 

 sivity of the positive and negative ions, or by centrifugal 

 separation, nor does it seem necessary to assume, with 

 Prof. Zeeman, that the magnetic effects are due to 

 electrons participating in the vortical motion. Since that 

 time 1 have recalled that, so far as definite evidence goes, 

 all luminous vapours giving a line spectrum, and therefore 

 capable of showing the Zeeman effect, are positively 

 charged. .\ flame coloured with sodium or lithium vapour 

 and placed between two condenser plates is attracted by 

 the negative plate. This fact was used by Lenard to 

 determine the velocity of the positive ions. .As shown by 

 Riecke and Stark (Phys. Zeit., v., 537, 1904), if a sodium 

 or lithium salt is placed on the kathode of a long spark the 

 coloured vapour remains in that neighbourhood ; if placed 

 on the anode it is at once projected across the entire 

 length of the gap. Hemsalech (Comptes rendus, cxlii., 2, 

 iqo6) proved spectroscopically that the metallic vapour in 

 the spark is projected solely from the positive electrode. 

 .\s shown by Stark [Ann. der Phys., xiv., 529, 1904), that 

 part of the luminous vapour in a mercury arc which gives 

 a band spectrum is unaffected by an electric field, while 

 that part which gives a line spectrum is positively charged. 

 The canal and anode rays are likewise examples of 

 positively charged carriers giving a line spectrum. 



What 'becomes of the negative electricity in these cases 

 is obscure ; but the fact remains that somehow, either in 

 the form of projected electrons or more rapidly moving 

 negative ions, it gets away, and leaves behind the posi- 

 tively charged ions of the luminous vapour. If such is 

 the case on the earth, we should expect it to be true of 

 the luminous vapours of hydrogen, calcium, and other 

 elements on the sun. Whether the vapours taking part in 

 the sun-spot vortices are positively charged can easily be 

 determined from Prof. Hale's observations on the Zeeman 

 effect. 



It would be interesting to know whether the solar 

 vortices follow a definite cyclonic law, as is the case in 

 the earth's atmosphere. If so, a definite resultant polarity 

 should be produced by the aggregate of sun-spots, and 

 accompanying magnetic fluctuations on the earth should 

 be always in one direction. If the vortices are accidental 

 the terrestrial effects should be irregular. 



