58 



NATURE 



[Nov. 1 6, 1876 



itself ought also to form a pseudomorphic deposit of the same 

 kind. 



Accepting, then, Sir Wyville Thomson's theory, the matigan- 

 iferoUs deposit might be accounted for as follows : — 



Manganese occurd in sea-water in very small quantities, suf- 

 ficient, nevertheless, for detection. Forchammer has detected 

 it together with iron and silica ; as also have Figuer and Mialhe.^ 

 It is, besides, almost invariably found in the watersTof some 

 springs, according to Prof. T. Sterry Hunt,^ and spring-water 

 sooner or later finds its way to the ocean. Again, it is found in 

 the ashes of plants,^ and it is therefore not unlikely that it may 

 be secreted by other organisms, such as foraminifera, molluscs, 

 &c. — in fact, Bischof found in the outer scale of oyster-shells 

 o'6i per cent, of ferric oxide, with some oxide of manganese* — 

 and as its carbonate is isomorphous with that of lime and iron, 

 it is perfectly probable that these should be found associated 

 together, as indeed they usually are. Supposing, then, Globigc- 

 rina shells to consist of carbonate of lime, with small traces of 

 carbonate of iron, carbonate of manganese, peroxide of iron, 

 and silicate of alumina, the following changes might take place 

 while the shell was passing through water charged with carbonic 

 acid gas and oxygen. 



All the carbonates would first be dissolved. Then the car- 

 bonates of iron and manganese would be oxidised, as they readily 

 part with carbonic acid in presence of oxygen, and the liberated 

 carbonic acid would, no doubt, act on a fresh portion of the 

 mixed carbonates. The silicate of alumina and peroxide of iron 

 already in the shell ' would not be affected. Thus there would 

 be a continual deposition of silicate of alumina, peroxide of iron, 

 and peroxide of manganese, very likely both hydrated. It is 

 taken for granted here that the red clay is merely a silicate of 

 alumina coloured by peroxide of iron, and not a double silicate 

 of iron and alumina. It does not seem quite clear which is 

 really meant in any of the reports. Alumina is found in small 

 traces in river- and sea-water, perhaps in many cases as the sili- 

 cate, which is soluble in minute proportions. Or it might origi- 

 rally exist as sulphate, in that state enter into the structure of 

 marine organisms, and subsequently undergo alteration to sili- 

 cate. Alumina has been found in small quantities in plants, but 

 how combined is not yet known. 



I believe the principal deposits of manganese ores are found 

 in connection with limestone or dolomitic rocks, probably for the 

 most part originally disseminated through them in small propor- 

 tions, and subsequently concentrated in particular localities by 

 the action of infiltrating water, and the nearest approach to the 

 phenomenon described by Sir Wyville Thomson appears to be 

 met with in the associated limestone, dolomite, iron ore, and 

 nodular manganese ore of the Lahn district, as recorded by 

 Bischof. ' At the place where the iron and manganese beds are 

 worked, there are several clay beds, varying from a iG."^ feet to 

 several fathoms in thickness. These Bischof considers are the 

 result of the continuous action of water containing carbonic acid, 

 the argillaceous limestone being converted into clay. The man- 

 ganese and iron ores lie beneath the clay beds, and it is most 

 likely that these minerals were extracted from the argillaceous 

 limestone at the same time as the carbonate of lime, having 

 doubtless existed in small quantities as carbonates in the 

 organisms forming the mass. In fact the lower clay beds still 

 contain s«me manganese. There is thus considerable analogy 

 between the two cases, the difFerence,being that these old lime- 

 stones having been formed in mass, in not very deep water, were 

 not liable to be dissolved — immediately on the death of the 

 organisms whose skeletons they were — by the action of sea-water, 

 that part being played ages afterwards by atmospheric water. 

 The result has been mainly the same, however, viz. , the produc- 

 tion of clay from the limestone, together with nodular man- 

 ganese. Possibly had the corals, &c., forming that limestone 

 had the opportunity of falling slowly, and each isolated, through 



' Bischof, " Chem. Geo.," vol. i., pp. 99-108. 



^ " Chem. and Geo. Essays," p. 143. 



3 Fownes' "Man. of Chem.," p. 469 ; also Watts' "Chem. Diet." 



* Op. cit., vol. i. , p. 198. 



5 It may be that there is a trace of uncombined ferric oxide already in 

 thtse shells, since the Glohigeiina ooze, when treated with very dilute acid, 

 leaves a red sediment like the "red clay" (see k" The Cruise of the 

 Challenger, Nature, vol. xlv. p. 96). Sir Wyville hesitates to claim for 

 'l!^ v'n**^^ of alumina and peroxide of iron that they exist in that form in 

 the shells, rather supposing them to be products of alteration. But the latter 

 IS certainly found in some shells and in red corals. It has been shown by 

 ITof. A. H. Church that the red chalk of Hunstanton, treated with very 

 weak acid, yields a residue closely resembling the dtep-sea "red clay."— 

 Chem. News, xxxi. p. 199. ■' 



6 Of. cif., vol, iii. p. 193. 



a sufficient depth of sea-water, the result would have been a 

 manganiferous mud, similar to these deep-sea clays. 



As to the nodular structure of the manganese oxide, it is of 

 course referable to the same mysterious molecular attraction 

 which determines the segregation of all the carbonate of iron in 

 the case of clay-ironstone in fire-clays and .shales, and silica, as 

 in chalk flints. 



Since the above was written, the last number of the Proceedinqs 

 of the Royal Society (vol. xxiv. No, 170), with Preliminary 

 Reports on the Cruise of the Challenger^ by Sir C. Wyville 

 Thomson and colleagues, has come to hand. These reports 

 contain a full description of the manganiferous muds, but no 

 theory as to the origin of the manganese is as yet put forward. 



Edward T. Hardman, 



Kilkenny H.M. Geological Survey, Ireland 



Mr. Wallace on the Distribution of Passerine Birds 



In Mr. Wallace's recently-published work on Geographical 

 Distribution, in more than one place the results arrived at from 

 an inspection of his elaborate tables of genera and families do 

 not agree with the numbers he uses in considering the general 

 bearing of the facts adduced. Thus in his " General Remarks 

 on the Distribution of the Passeres," vol. ii. pp. 299-302, he 

 says (I.e. p. 300): " The families that are confined to single 

 regions are not very numerous, except in the case of ihe Neo- 

 tropical region, which hasyfz'^, the Australian has ov\'^ ihi-ee, the 

 Oriental one, Ethiopian one, and the other regions have no 

 peculiar families." Adopting his tables of the families of the 

 Passeres, I find the numbeis should be really as follows : — 



Neotropical 7 ... Fams. Nos. 39^, 40, 41, 42, 44, 45, 46. 



Australian 5 ... ,, ,, 21,22,25,49,50. 



Oriental 3 ,, ix, 12, 43. 



The Nearctic region should also be mentioned as possessing 

 one peculiar family, i.e. ChaniDeidse. The statement that none 

 of the turdoid Passerine families are exclusively American must 

 also be modified to meet this fact. There are three families [i.e. 

 Paictidae, Pittidje, Eurylsemidae), instead of tivo, of the P"ormica- 

 rcid Passeres in the Old World, of which the Pittid^e can hardly 

 be said to have only a " very restricted distribution." 



The Australian genus Struthidea, of doubtful position, seems 

 omitted altogether. W. A. Forbes 



Cambridge, Oct. 30 



Antedon Rosaceus (Comatula rosacea) 



There are one or two rather hasty conclusions in the letters 

 you have recently published upon the feather-star, which I will 

 take the liberty of pointing out. My friend, Major Lang, 

 arguing from his experience in Torbay, says : " It is evident 

 that the habitat of Comatula is strictly defined, viz., in compara- 

 tively deep water, and amongst rocks." Last year, however, I 

 took it in Salcombe Estuary, in shallow water, and not among 

 rocks, but among the Zostera marina, to which numbers of the 

 young stalked form were sticking. The well-known marine 

 zoologist, Mr. Hincks, tells me that he took both the adult and 

 stalked forms in great abundance in the same locality more than 

 twenty years ago. 



The President of the Birmingham Natural History and Micro- 

 scopical Society, in commenting upon Major Lang's letter and 

 other notices of the capture of the feather-star, says, " It is a 

 most remarkable circumstance, therefore, that in the space of 

 about three years, the species should have become numerous to 

 the extent alluded to by Major Lang, more than a hundred being 

 taken in one haul of the dredge." But this rapid increase in the 

 numbers of the species since 1873 is imaginary, for dredgings in 

 the two previous years had yielded the adult form by bucketsful 

 from the neighbourhood of the Thatcher Rock. 



In regard to the name, orie can only wish for a scientific dic- 

 tator to;,restore Lamarck's happily appropriate designation Co- 

 matula, in place of the earlier name, Antedon, the meaning and 

 pronunciation of which are alike difficult to determine. It would 

 be interesting to learn from political economists, in what category 

 of labour, productive or unproductive, those investigations should 

 be reckoned, which end in displacing some name universally 

 received and understood in favour of one forgotten and obsolete. 

 Justice to the ancient observer is pleaded as a chief reason for 

 these revivals. But it is a poor renown to have helped to in- 

 crease the ever-growing burden of scientific nomenclature. 



Torquay, Nov. 6 Thomas R. R. Stebbing 



