March 25, 1880] 



NATURE 



491 



and Haime on that account as a special division of the 

 corals, the Zoantharia labulata. 



By the researches of the late Prof. Agassiz, Prof. 

 Verrill, Mr. Moseley, and others, these peculiar structures, 

 the tabulae, on which MM. Milne Edwards and Haime 

 relied as the foundation of a natural group, have been 

 proved to be of very secondary importance, and to exist 

 in corals of most widely different structure in other and 

 more essential particulars. 



Prof. Nicholson, in his preliminary review of the various 

 different forms thus formerly brought together, describes 

 the most important structural details of each, and assigns 

 them to their several places in the animal series. Some, 

 as Heteropora, are, according to the late researches of 

 Mr. Busk, of Bryozoan affinity, and Mr. Busk's results 

 have been so very recently obtained that this fact can 

 only be explained in the book in a note appended to the 

 preface. The Milleporidas and their allies are Hydroids, 

 the Helioporidac and Heliolites Alcyonarians, the Pocillo- 

 poridae Madreporarians. The Favositidae and Syringo- 

 poridie, notwithstanding the close relationship of the 

 latter, in general appearance to the Tubiporine Alcyo- 

 narians, the author refers, contrary to the opinion of 

 Dana, Haeckel, and Zittel, to the Madreporaria, expecting 

 " that they will find a place, though a special one, in the 

 series of the Zoantharia perforata" 



Twelve groups of tabulate corals in all are reviewed, 

 namely, the Milleporidas, Pocilloporidae, Favositidas, 

 Colummariadae, Syringoporidoe, Auloporidas, Halysitidae, 

 Tetradiidae, Thecidae, Helioporidae, Chaetetidx, and 

 Labechidae. It is to be hoped that so heterogeneous an 

 assemblage will not be placed again side by side in 

 scientific works, now that the wide differences by which 

 its components are naturally separated are fully known. 

 Succeeding the general introduction there follow in the 

 book a series of chapters devoted to the description of the 

 peculiarities of the families and genera of those of the 

 above cited families of corals which are of Palaeozoic age, 

 with detailed descriptions of certain selected types and 

 discussions on the affinities of each family, the affinities 

 being in many cases as yet obscure. 



The text is illustrated by excellent woodcuts, and there 

 are fifteen plates containing details of the structures of 

 various forms as exhibited in microscopic sections. The 

 whole cannot but prove of value to specialists who occupy 

 themselves with the investigation of these difficult fossil 

 organisms ; but the matter of the book is necessarily too 

 technical in character to allow of detailed review with 

 advantage to the readers of Nature. Some of the 

 descriptions of types and figures have appeared already 

 in the Annals and Magazine of Natural History. 



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Dissociation of the Metalloid Elements 

 In the account given in Nature, vol. xxi. p. 445, of M. Raoul 

 Pictet's proposal to dissociate the metalloid elements the follow- 



ing reason is given as the ground of his belief that these elements 

 are compounds : — 



"The spectrum of the sun when scrutinised with the most 

 elaborate skill and knowledge reveals another very striking cir. 

 enmstance. A large number of the substances regarded by the 

 chemist as elements have now been recognised by the charac- 

 teristic absorption lines of their spectra as existing in the heated 

 matters surrounding the fun. The researches of Mr. Lockyer 

 show that nearly forty of the metals are thus to be detected. 

 But not a single metalloid is thus discoverable. Indeed so 

 marked is their absence that the presence of hydrogen in Mich 

 great abundance is held by no less an authority than Mr. Dumas 

 to be a convincing proof that hydrogen is a metal and not a 

 metalloid." 



M. Pictet is doubtless unaware that fcr many years I have 

 advocated the same conclusion. The grounds I have given for 

 this belief are twofold, firstly, that the peculiar chemical reactions 

 of these elements on which the law of even numbers rests leads 

 to this result ; and, secondly, that no spectrum of any one of 

 these elements has as yet been found in the light of the sun or 

 fixed stars. Oxygen, I may say, is not included in my list. My 

 first published observations on this subject date from the years 

 1S66-1S67 ("Calculus of Chemical Operations," part 1, Trans. 

 R. S., 1S66, p. 859, and Chemical News, June 14, 1867, p. 502). 

 Last year I bad occasion to recur to this question, and in an 

 article by myself in the Philosophical Magazine, June, 1S79, 

 p. 430, the following passage occurs : — 



" It is a significant fact that a very large proportion of the 

 class of elements which I have termed composite elements have 

 not been found in the sun. In reply to inquiries on my part Mr. 

 W. Huggins writes to me thus :— So far as I know, nitrogen, 

 ph ,rus, arsenic, antimony, boron chlorine, iodine, bromine, have 

 not been found in the sun. In one paper Lockyer suspects iodine. 

 Dr. Miller and I found coincidence of the three lines of antimony 

 with three lines in Aldebaran. Though this observation would 

 show considerable probability of antimony in star, I do not think 

 the spectroscope (two dense prisms of Hint glass) was sufficiently 

 powerful to make its existence there certain. In the ca e of 

 nitrogen, no coincidence was observed in any of the stars. In 

 my paper in the Transactions of the Royal Society on S] ectra 

 of Nebulre, I show coincidence of principal line with the strong 

 line in spectrum of nitrogen. Now this line of nitrogen is a 

 double one ; and I was not at first able to be certain if the line 

 in the nebula was similarly double. Subsequently with the 

 powerful spectroscope I used for the motions of stars, I was able 

 to make a certain determination of this point {Proceedings, R. S., 

 1S72, p. 3S5). I found the line in the nebula single and coin- 

 cident with the middle of the less refrangible of the components 

 of the double line. 



Nitrogen Red 



I say ' middle ' because the line in the nebula is narrower and more 

 defined than either of the two lines forming the double line. I 

 made experiments to see if under any conditions of pre 

 temperature the more refrangible of the two lines fades out, s.o 

 as to leave only the one with which the line in the nebula is 

 coincident. I did not succeed. So the matter stands. Is 

 nitrogen compound? Are there any conditions under which the 

 one line only appears ? Has the line in the nebula no real con- 

 nection with nitrogen further than being sensibly of the same 

 refrangibility ? 



" Now we must either consider that the matter of these elements 

 so abundant on the earth does not exist in the sun or stars (which 

 is hardly probable), or that they have passed into forms of com- 



