October 6, 1910J 



NATURE 



433 



growth within it and b\' material washed into it over 

 the barrier. It may be so, but it does not justify the 

 statement that "atoll lagoons tend, as a rule, to 

 become smaller and shallower," and there is no 

 attempt by reference to other atolls to justify it. 

 Solution and material swept out by the tides are said 

 to have nothing to do with the formation of the 

 lagoons of atolls. The picture of a high island 

 crumbling to pieces within the calm of an encircling 

 barrier reef appears to our author to be contrary to 

 all natural laws. On what view does he explain 

 Agassiz's wonderful series of photographs of Fijian 

 islands within barrier reefs? "In this (his own) de- 

 scription," he states, " it is assumed throughout that 

 the lagoon is a slightly submerged reef"; why this 

 assumption without evidence? The encircling reef is 

 said to be "a mosaic inlay of coral fragments, 

 cemented together into a solid platform," but there 5s 

 no evidence that it was ever really examined. It is 

 supposed to have grown up as a platform, and many 

 of its constituent organisms must surely have re- 

 mained in their growth-positions. A similar platform 

 is found at 13 feet above mean tide level ; it is stated 

 that such a platform can only be formed below this 



Fig. 2. — Photograph of 

 of the genus Scania 

 by the fish. From ' 



The black li 

 Coral and Atoll: 



ed Uiad Coral Rock, to show I 

 irks the edge of the alga covering 



level, and its existence is explained as due to eleva- 

 tion. 



Our author does good service in directing attention 

 to the important effects of sedimentation. Sedimen- 

 tation banks largely form the foundations of reefs, 

 but " it matters not what the base mav be so long as 

 its platform comes within the wind-stirred area." 

 " .\nv elevation which rises to this plane (the Umititig 

 line of sedimentation) will furnish the corals with a 

 suitable basis." The depth of this line varies. It is 

 entirelv a supposititious line, and, so far as we can 

 understand, mav lie at any depth. Direct investiga- 

 tion on the processes of sedimentation in the ocean 

 is certainly needed. 



In conclusion, it cannot be said that Dr. Wood- 

 Jones has much new to tell us. His volume is, how- 

 ever, a very readable one, and most suggestive of 

 lines of research on corals, which might profitably be 

 pursued by more precise methods. His range of in- 

 vestigation and reading were obviouslv too restricted 

 to enable him to draw conclusions as to the formation 

 of coral reefs in general. The account of the fauna 

 and flora is very good, and the note on Scarus as a 

 coral-feeder interesting. The illustrations of corals 



NO. 2136, VOL. 84] 



and other organisms are good, but a specialist should 

 have been consulted, so that the names of the coral 

 genera might have been inserted. An obvious Actinian 

 (p. 161) would not then have been labelled as an 

 Alcvonarian. 



RESEARCHES IN STELLAR PARALLAX.^ 

 'X'HE Observatory of Yale College has acquired a 

 ■*■ deservedly high reputation for the 2eal with 

 which the staff has prosecuted the inquiry into stellar 

 parallax and the standard of accuracy consistentlv 

 maintained. This latest contribution to the subject 

 cannot but enhance that reputation for accuracy, for 

 the results sought do not aim so much at applying the 

 method to fresh instances, as to the re-examination 

 of previous investigations with the view of improving 

 their trustworthiness. Of the stars, the distances 

 of which are here discussed, two-thirds have already 

 been the subject of inquiry at Yale or elsewhere, but 

 on various grounds the results have been regarded 

 with a degree of suspicion that made the repetition 

 of the measures desirable. 



The new material falls into two classes, one con- 

 taining stars having a larger 

 annual proper motion than about 

 o'4" ; the other, selected stars in the 

 Pleiades the observation of which 

 might afford evidence as to the dis- 

 tance of the group as a whole. As 

 the results derived from these 

 Pleiades stars are not regarded as 

 conclusive, and do not enter into 

 the final catalogue, they may be 

 dismissed here. One star gave the 

 value zero, indicating that the 

 Pleiades group is at the same dis- 

 tance as the star ; the measures of 

 another assigned the small negative 

 parallax of —0.3", "a value that 

 would give a possible limit of sys- 

 tematic error"; while the third 

 series, resulting in the value -l-o'6", 

 suggests that the star does not 

 belong to the group at all, but is 

 nearer to our system, " and this 

 result would seem to be fairly 

 assured." The approximate dis- 

 tance of the Pleiades .group still 

 remains a matter of conjecture. 

 Naturally in a work so long and laborious, difficul- 

 ties arose in connection with the instrumental and 

 optical equipment, necessitating interruptions in the 

 continuance of the sequences. The most formidable 

 of these was a tendency for the field lens of the eye- 

 piece to work loose, to which inconvenience it is not 

 necessary to refer further, than to express our assur- 

 ance that the skill and experience of the observers 

 would succeed in effectually removing any traces of 

 systematic error arising from this untoward accident. 

 To show that this confidence is warranted, we may 

 give the final results obtained by the three observers 

 in the case of the Arcturus determination, a star the 

 measures of which have been most scrupulously 

 examined, since for a star of such brilliancy and large 

 proper motion the earlier values of parallax were so 

 suspiciously small, as to suggest that some inherent 

 quality in' the star itself, such as colour, or some 

 peculiaritv in the observers' method of measuring, had 

 influenced the result. With regard to the detection of 



1 Transactions of the Astronomical Observatory of Yale University 

 Vol, ii.. part ii. Parallax Investigations on thirty-five =elect;d stars by 

 Frederic L. Chase, Mason F. Smith, and William L. Elkin (Director). 

 (New Haven : Published by the University, igio.) 



bitten away 



