49Q 



NATURE 



[March 25, 1880 



At the November meeting of the Cambridge Philo- 

 sophical Society in 187S, I drew attention to some re- 

 markable changes which the outline of the solar corona 

 had undergone during recent years ; the change seemed 

 to be periodical, and the period seemed to be that of the 

 sun-spots. In the Observatory tor December I also made 

 some remarks to the same effect. Pp. 496-501 of the 

 volume before us contain short descriptions of the general 

 shape of the corona during all the eclipses, of which we 

 have drawings, and in all cases information on the number 

 of sun-spots is given. 



The result seems to be altogether in favour of such a 

 relation between the two phenomena as I have pointed 

 out. In the papers above referred to, as well as at the 

 November meeting of the Astronomical Society in 1S7S, 

 I also pointed out a still more remarkable, though perhaps 

 more doubtful, coincidence. It is generally found that the 

 symmetry of the corona is not cornplete, but that one side 

 is nearly always more fully developed, while the other is 

 more contracted ; and this departure from symmetry 

 seems to be related to a direction fixed in space. Thus 

 the eclipses of 1868, 1874, 1S75, 1878, which all happened 

 near the minimum of solar activity, resemble each other 

 in general character ; but in the eclipses of 1874 and 

 1875 the east ' side of the corona was much wider than 

 the west, while in 1868 and 1878 the west side was the 

 broadest. Now the eclipses of 1874 and 1875 happened 

 in April, while the eclipses of 1868 and 187S happened in 

 August and July. The eclipse of August, 1869, resembles 

 also the two last mentioned in this departure from sym- 

 metry, and the eclipse of December, 1871, does not show 

 any decided difference cither way. If this remarkable 

 connection of the general outline of the corona with the 

 heliocentric position of the earth at the time of the eclipse 

 should be confirmed, it would tend to show that the outer 

 corona at any rate is of cosmic origin, and this view would 

 be supported if it should be found, as is probable, that 

 the axis of general symmetry of the corona is not exactly 

 coincident with the solar axis. The connection between 

 the sun-spots and corona would, according to this view, 

 be reversed ; that is to say, the more disturbed state of 

 the corona at the maximum would not be produced by the 

 increase of sun-spots, but the sun-spots would ultimately 

 be produced by a cosmic cause which has the same 

 period. The next eclipse in 1 S82 will not unfortunately 

 throw much light on this question, as it will most likely 

 resemble the eclipse of 1870 or 1S71. 



The great value of the book before us lies in the many 

 suggestions for future observation which offer themselves 

 on its perusal. It teaches some lessons which all of us 

 who have ever observed eclipses or are likely to observe 

 them in future would do well to remember. Thus on 

 reading over the different and often conflicting accounts 

 of one and the same phenomenon, we are struck with the 

 insufficient descriptions of the apparatus and instruments 

 with which the observations have been made. We are 

 told by an observer what he has seen and what he has not 

 seen, but on trying to compare his account with that of 

 others, we generally miss some important information. 

 Observers with the spectroscope, for instance, generally 

 do not tell us anything, or at any rate they do not tell us 

 enough, about the width of slit which they have used and 



* Owing to a slip it was said in the Report on the Eclipse of 1875 that the 

 west side was the widest in 1874 and 1875. 



about the luminosity of their spectroscope. Observers 

 with the polariscope speak of bands, vertical or hori- 

 zontal, and their description generally fails where it is 

 most wanted, and we cannot decide whether a certain 

 polarisation has been observed, or one at right angles to 

 it. We ought, however, to exempt the Washington 

 observers from this general condemnation. The reports 

 emanating from the United States Naval Observatory are 

 generally a model in the accuracy of their accounts. 



The preparation of the eclipse volume has necessarily 

 taken a good many years, and it would have been useful 

 if some information had been given as to when different 

 parts of it have been written. The Report of the Eclipse 

 of 1875, for instance, appeared while the work was pro- 

 gressing, and it is natural, therefore, that only those 

 observations could be mentioned which referred to sub- 

 jects treated in the last few chapters. Yet some informa- 

 tion might have been given that the treatment of that 

 eclipse is only incomplete. The remark on p. 373 can 

 only have been written before Mr. Ranyard could have 

 known anything of the results which had been achieved. 



As a boo'c of reference to those interested in eclipse 

 observations, the present volume is, as we have already 

 mentioned, of very great value. Our thanks are due to 

 Mr. Ranyard for the great trouble he has taken in its 

 preparation. The blunders contained in it are so obvious, 

 as a rule, that they will hardly mislead any one who is 

 likely to make use of the book. Arthur Schuster 



NICHOLSON'S TABULATE CORALS 

 On the Structure and Affinities of the Tabulate Corals of 

 the Paleozoic Period, with Critical Descriptions of 

 Illustrative Species. By H. Alleyne Nicholson, M.D., 

 D.Sc, &c, Professor of Natural History in the Uni- 

 versity of St. Andrew's. (London and Edinburgh : W. 

 Blackwood and Sons, 1879.) 



THIS handsome post octavo volume contains a dis- 

 quisition on a rather heterogeneous assemblage of 

 organisms partly Ccelenterate and partly Bryozoan in 

 nature, partly of uncertain affinities. Of the palaeozoic 

 Ccelenterate corals described, the major portion are pro- 

 bably Alcyonarian. None of them, except perhaps 

 Labechia, appear to belong to the Hydroids, the family 

 of the Hydrocorallina? being, as far as has yet been 

 discovered, of comparatively recent origin, and not of 

 older date than cretaceous deposits at the most, unless, 

 as believed by Mr. Carter, Stromatopora and its allies of 

 the Silurian formations are in reality closely related to 

 Millepora. 



Prof. Nicholson, in the recent edition of his "Palaeon- 

 tology," places Stromatopora amongst the sponges, and 

 does not accept Mr. Carter's conclusions. He seems in 

 doubt about the true relationship of Labechia from the 

 Upper Silurian, the similarity in the structure of which to 

 the Milleporidae was first pointed out by Dr. Lindstrom. 

 The author himself, in conjunction with Dr. Murie, was 

 one of the first to investigate the finer structure of 

 Labechia, and described his results in a memoir on the 

 Stromatoporoids, in the Journal of the Linnean Society. 



The present work commences with a short review of 

 all those corals which possess tabula or transverse calca- 

 reous partitions within their pores or calicles, and which 

 were formerly grouped together by MM. Milne Edwards 



