March 15, 1877 J 



NATURE 



443 



science, but many genera are new though pertaining to Central 

 African types already known. The excellent condition of tlie 

 specimens, the care taken in selection of various stages and 

 characters of the plants, and descriptions taken on the spot by 

 Dr. Welwitsch have rendered Mr. Baker's study very complete 

 and satisfactory. — A technical descriptive paper by Mr. Charles 

 Knight on the Lichens of New Zealand, was taken as read. 

 — The Secretaiy also read a short notice of a new form of 

 Ophiuridre from the Philippines, by Mr. Edgar A. Smith. The 

 distinctive characters of tlie specimen the author regards as sub- 

 generic, and names it [Ophiomastix) Acantkarachna mirabilis. 



Zoological Society, March 6. — Dr. E. Hamilton, vice-pre- 

 sident, in the chair, — Mr. E. W. H. Holdsworth exhibited and 

 made remarks on a specimen of Geockhla layardi, from Ceylon. 

 — Prof. Owen, C.B., communicated some notes made by Mr. 

 G. F. Bennett, while exploring the burrows of the Ornithorhyn- 

 chus paradoxals, in Queensland, with comments on them. — A 

 communication was read from Lieut. -Col. R. H. Beddome, con- 

 taining the descriptions of three new snakes of the family 

 UropeltidK, from Southern India. — M. A. G. Butler read the 

 descriptions of some new species of Heterocerous Lepidoptera in 

 the collection of the British Museum, from Madagascar and 

 Borneo. Amongst the latter was the type of a new genus, pro- 

 posed to be called Mimeuplaa. — Mr. G. French Angas read a 

 paper in which he gave descriptions of a new species of Bulitmis 

 from Western Australia, and a Palndinella from Lake Eyre, 

 South Australia ; these he proposed to call respectively Buli?>ius 

 ponsonbyi, and Paludinella gilesi. — A second paper by Mr. Angus 

 contained the descriptions of one genus and twenty-five species of 

 marine shells from New South Wales. — Mr. Angus also read a 

 further list of additional species of marine mollusca to be 

 included in the fauna of Port Jackson and the adjacent coasts of 

 New South Wales, with remarks on their exact localities, &c., 

 thus bringing up the number of species now ascertained to in- 

 habit Port Jackson and the adjoining shores to a gross total of 

 693. — Mr, Phineas S. Abraham, M.A., B.Sc, read a paper 

 containing a revision of the Anthobranchiate Nudibranchiate 

 Mollusca. The paper comprised a general and historical intro- 

 duction to this group of Nudibranchs, i.e., those which bear the 

 branchiae upon the dorsal surface, more or less surrounding the 

 arms, and allusion was made to all the principal work which had 

 bten done upon these animals. The second part consisted of 

 definitions of the larger divisions and of the genera, with the 

 enumeration, synonyma, references to and habitat of, as far as 

 possible, every species hitherto published. In the last general 

 list, viz., that by H. and A. Adams, but 163 forms were men- 

 tioned ; this list included 457. The third part contained de- 

 scriptions of forty-one hitherto undescribed species belonging to 

 the genera Doris, Ckrotnodoris, Hexabranchus, Acanihodoris 

 and Doridopsis. — A communication was read from the Count 

 Salvadori, containing notes on some birds mentioned by Dr. 

 Cabanis and Mr. Reichenow, as collected in Papuasia and in the 

 Moluccas during the voyage of the Gazelle. 



Geological Society, February 21. — Prof. P. Martin Duncan, 

 F. R. S., president, in the chair. — Samuel Arthur Adamson, 

 William Mason Cole, Thomas Floyd, William Stukeley Gresley, 

 Edward Pritchard, Joseph Pryor, and John Gwillim Thomas 

 were elected Fellows of the Society. The following communi- 

 cations were read : — On possible displacements of the earth's 

 axis of figure produced by elevations and depressions of her 

 surface, by the Rev. J. F. Twisden, M.A., Professor of Mathe- 

 matics in the Staff College. Communicated by John Evans, 

 F.R.S. The object of this paper is to discuss the question of 

 the possibility of a displacement of the earth's axis of figure 

 under the conditions indicated in a question (suggesting the 

 possibility of a displacement of the axis of figure from the axis 

 of rotation, amounting to 15" or 20°) put to mathematicians in a 

 passage of the Anniversary Address delivered to the Society by 

 its president, Mr. J. Evans, on February 18, 1876. The treat- 

 ment of the question is kinematical ; the forces by which the 

 elevations and depressions might be effected do not come under 

 discussion. In determining numerically the amount of the devia- 

 tion from the formulas investigated, approximate numbers seem 

 to be sufficiently exact for every useful purpose. The conclu- 

 sions arrived at are as follows : — (i) The displacement of the 

 earth's axis of figure from the axis of rotation that would be 

 effected by the elevations and depressions suggested in the ques- 

 tion above referred to would be less than 10' of angle. (2) A 

 displacement of as much as 20° could be effected by the eleva- 

 tions and depressions of the kind suggested only if their heights 



and depths exceeded by many times the height of the highest 

 mountains. (3) Under no circumstances could a displacement 

 of 20" be effected by a transfer of matter of less amount than 

 about a sixth part of the whole equatorial bulge. (4) Even if a 

 transfer of this quantity of matter were to take place, it need not 

 produce any effect, or only a small effect, on the position of the 

 axis of figure, e.g., if it took place in a way resembling that sug- 

 gested in the question, it would produce a displacement amount- 

 ing to but a small part of 20". (5) If, however, we suppose a 

 deviation of the axis of figure from the axis of rotation amount- 

 ing to as much as 20° to have been by any means brought about, 

 the elTect would be to cause a sort of tidal motion in the ocean, 

 the greatest height of which would tend to be about twice the 

 depth of the ocean. The author suggests as probable that the 

 efTect of this tendency would be to cause the ocean to sweep over 

 the continents in much the same way that a rising tide sweeps 

 over a low bank on a level shore. (6) The notion that a large 

 deviation of the earth's axis of figure from its axis of revolution 

 may be efTected by elevations and accompanying depressions is 

 at first sight an inviting way of bringing polar lands into lower 

 latitudes, and thereby accounting for the more genial climate 

 that is believed to have once prevailed in such countries as 

 Greenland. The investigation by which the above results have 

 been obtained seems to show that the desired explanation is not 

 to be sought in the direction indicated by Mr. Evans's question. 

 Whether there is any other agency by which a gradual displace- 

 ment of the pole geographically could be effected is a question 

 of far wider scope than that discussed in the present paper, 

 and one which the author does not profess to determine.^ 

 — Note on a specimen of Diploxylon, from the coal-formation 

 of Nova Scotia, by J. W. Dawson, F.R.S. The author de- 

 scribed the occurrence in Coal-measure sandstone at the South 

 Joggins of an erect stump of a Sigillarian tree 12 feet in length. 

 It originated in a coaly seam 6 inches thick, and terminated 

 below in spreading roots ; below the coal-seam was an under- 

 clay 3 feet 4 inches thick, separating it from an underlying seam 

 of coarse coal. The stem, which tapered from about 2| feet in 

 diameter near the base to i^ foot at the broken end, was a sand- 

 stone cast, and exhibited an internal axis about 2 inches in dia- 

 meter, consisting of a central pith cylinder, replaced by sandstone, 

 about -?- inch in diameter, and of two concentric coats of scalari- 

 form tissue, the inner one ^V ii^ch in thickness, the outer consti- 

 tuting the remainder of the axis. The scalariform tissue of the 

 latter was radially arranged, with the individual cells quadran- 

 gular in cross section. A few small radiating spaces partially 

 filled with pyrites obscurely represented the medullary rays, 

 which were but feebly developed ; the radiating bundles, passing 

 to the leaves, ran nearly horizontally, but their structure was 

 very imperfectly preserved. The cross section, when weathered, 

 showed about twenty concentric rings ; but these under the 

 microscope appeared rather to be bands of compressed tissue 

 than true lines of growth. The thick inner bark was replaced 

 by sandstone, and the outer bark represented by structureless 

 coal. On a small portion of one of the roots the author traced 

 the remains of stigmarioid markings. From the above characters 

 the author identified this tree with Diploxylon of Corda, and 

 stated that it was the first well-characterised example of this type of 

 Sigillarians hitherto found in Nova Scotia. The author compared 

 the structure of this stem with that of other Sigillarians, and re- 

 marked that it seemed to come within the limits of the genus Sigil- 

 laria, but to belong to a low type of that genus approaching Lepi- 

 dodendron in structure; those of the type of .S". elegans, Br., and 

 S. pinulosa, Renault, being higher in organisation, and leading 

 towards the still more elevated type described by him in 1870. 

 He further discussed the supposed alliance of these trees with 

 Gymnosperms, and the probability of the fruits known as Tri- 

 gonocarpa being those of Sigillaria, and expressed the opinion 

 that the known facts tend to show that there may be included in 

 the genus Sigillaria, as originally founded, species widely differ- 

 ing in organisation, and of both Gymnospermous and Acrogenous 

 rank. 



Royal Microscopical Society, March 7. — H. C. Sorby, 

 F.R.S., president, in the chair. — A letter received from Mr. 

 Frederick Ebsworth, Australia, descriptive of a supposed new 

 method of using the micrometer, which the author had found 



' The first draught of the paper, of which the above is an account, was 

 drawn up last August, and was shortly after sent to Mr. Evans. It was 

 written independently of the wider view of the subject taken by Sir W. 

 Thomson in his Address delivered at the last Meeting of the British Asso- 

 ciation, and by Mr. G. Darwin in his paper, of which an abstract has been 

 published in No. 1^5 of the Proceedings of the Royal Society. 



