450 



NATURE 



[March 8 1894 



(3) Sphenophylhim. — As is well known, the slender jointed 

 stem bore verticils of superposed leaves, the number of which, 

 in each whorl was some multiple of 3. In S. plurifoliatum, 

 the species first described, the leaves probably numbered 18 in a 

 wliorl. The primary wood was triarch and centripetal, and so 

 far resembled that of certain Lycopodiacese, with which, how- 

 ever, the genus has otherwise little in common. Abundant 

 secondary tissues were formed. The cambium can be clearly 

 demonstrated, and occupies the normal position between wood 

 and bast. Sieve tubes have been detected in the phloem of S. 

 insigne. Internal periderm was formed, giving rise to a regular 

 scale-bark. 



The fructification of Sphenophylhim, as has been shown by 

 M. Zeiller, is that previously described under the name of Bow- 

 manites Dawsoni. The axis of the strobilus bore numerous 

 whorls of partially coherent bracts. The very long sporangia- 

 phores, each bearing a single recurved sporangium, arise from the 

 upper surface of the whorl, two sporangiophores corresponding 

 to each bract. The whole structure is quite unlike that of any 

 other vascular cryptogam. The plant, so far as observed, was 

 homosporous, and the alleged heterospory of another species is 

 very doubtful. The genus is entirely isolated, and, though 

 the structure is now completely known, its affinities cannot be 

 determined until additional forms have been discovered. 



March r. — "Researches on the Structure, Organisation, and 

 Classification of the Fossil Reptilia. Part IX. Section i. On 

 the Therosuchia." By H. G. Seeley, F. R.S. 



This paper discusses the classification of reputed Permian and 

 Triassic Reptilia which have been referred to the Anomodontia 

 as Theriodonts. 



Prof. Cope's definition of the Theriodontia as distinguished 

 from the Anomodontia by characters of the post-orbital arch is 

 regarded as unsupported by evidence. The author would limit 

 the Theriodontia to animals which conform to Sir R. Owen's 

 original definition based on the dentition (1876), and have tem- 

 poral vacuities and a small quadrate bone. 



It appears that there is a series of groups of South African 

 Reptilia which agree in having a palate which has some resem- 

 blances to mammals but approximates to Sphenodon, lizards, 

 and crocodiles. All these sub-orders are combined as the 

 Therosuchia. In this order or group may be included the 

 Deuterosauria from the Permian rocks of Russia. 



The relation of the Therosuchia to other Anomodontia is shown 

 in the following grouping :- — 



Therosuchia. — Pareiasauria, Procolophonia, Gorgonopsia, 

 Dinocephalia, Deuterosauria, Theriodontia {Lycosauria, Cyiio- 

 dontia, Gomphodontia), Endothiodontia [Theromora]. Thero- 

 CHELONIA. — Dicynodontia, Kistecephalia. Mesosauria. 



" Researches on the Structure, Organisation, and Classifi- 

 cation of the Fossil Reptilia. Part IX. Section 2. On the 

 Reputed Mammals from the Karroo Formation of Cape Colony. " 

 By H. G. Seeley, F.R.S. 



The author re-examines the remains of Iheriodesmus, and 

 contests the interpretation of the carpus given by Prof. Bardele- 

 ben, producing specimens of South African reptiles in which 

 there is a single bone beneath the radius, as in Theriodes7ntts. 



" Researches on the Structure, Organisation, and Classifi- 

 cation of the Fossil Reptilia. Part IX. Section 3. On Diade- 

 modon." By H. G. Seeley, F.R.S. 



The author describes fragments of jaws and teeth from Upper 

 Karroo strata at Wonderboom and Aliwal North, collected by 

 Messrs. R. D. Kannemeyer and Alfred Brown. They may 

 possibly belong to more than one genus ; but, in absence of 

 sufficient knowledge of the skull to establish differences, the four 

 species are referred to a new genus, Diademodoii. 



The teeth are highly specialised, but distinct in plan from 

 Tritylodon, and from all known reptiles They closely approxi- 

 mate to some of the higher mammalia. The author refers 

 Diadentodon to a division of the Theriodontia in which the teeth 

 become worn with use, which is named Gomphodontia. 



Physical Society, February 23.— Prof. A. W. Rlicker, 

 F.R.S., President, in the chair. — A note on a new electrical 

 theoreui was read by Mr. T. II. Blakesley. Two or more dis- 

 positions of electromotive forces in any network of conductors 

 which produce at every part of the network the same currents, 

 are defined as eqidvalent systems. The following theorem is 

 then stated and proved : In any system of conductors possessing 

 seats of electrom)tive force at any number of points, if any of 

 these sources be moved along the various bars of the conducting 

 system, and where a point of junction is encountered, each 



NO. I 27 I, VOL. 49] 



becoming a seat of the same electromotive force in each of the 

 newly encountered bars, then the disposition at any moment is 

 equivalent to that at any other moment, and therefore to the 

 original disposition. Equivalent systems might also be defined 

 as being such as produce equal expenditure of power in each part. 

 From the above theorem the following propositions are deduced 

 by the author : (i) That if any closed surface contains a portion 

 of a network, then an electromotive force in any bar cutting 

 the surface can be replaced by equal electromotive forces (in 

 opposite directions as regards the surface) in all the other bars 

 cutting the surface, without disturbing the current in any part of 

 the network. (2) If two systems pi electromotive forces be 

 equivalent, one may be derived from the other. — Prof. C. V. 

 Boys, F.R.S., read a note on the attachment of quartz fibres. 

 When torsion fibres are required to carry large weights ap- 

 proaching the breaking weight, the ordinary method of attach- 

 ment by shellac is not always satisfactory, for if the part of the 

 fibre in the cement is twisted or bent, the yielding of the shellac 

 causes uncertainty of zero. To avoid these troubles, Prof. Boys 

 has devised and perfected a method of soldering the fibres, full 

 details of which are given in the paper. After selecting a fibre 

 of the right diameter and length, small weights are fixed on the 

 ends by shellac. The end parts are then cleaned by dipping in 

 strong nitric acid, washed, silvered, and electro- coppered. The 

 weights are then cut off, and the coppered ends soldered to tags 

 of tinned metal foil, chloride of zinc being used as a flux, and 

 its capillarity serving to hold the ends to the tags whilst the 

 latter are heated. The superfluous copper and silver are dis- 

 solved off by nitric acid, the tags and solder being protected by 

 beeswax. After washing in boiling water the fibre is ready for 

 use. Melted shellac is used for securing the tags to the torsion 

 rod and suspended body. Several ingenious details of pro- 

 cedure to avoid capillary difficulties in the cleaning, plating, and 

 washing processes are described in the paper. If fibres are 

 required to conduct electricity, they are silvered and washed after 

 the tags have been soldered on. Such fibres the author considers 

 essential for making connection with electrometer needles of 

 the greatest delicacy, for liquid connections are fatal to stability. 

 Methods of rendering fibres visible by smoking with arsenic or 

 magnesium are mentioned in the paper. At the meeting a per- 

 fectly circular hole, TnjVrr of an inch in diameter, made by sold- 

 ering round a quartz fibre passing through a hole in a metal 

 plate, and then drawing out the fibre, was exhibited under a 

 microscope. Mr. Inwards asked if the shellac used to secure 

 the tags was melted or dissolved. Mr. Blakesley inquired if 

 silvering fibres did not destroy their perfect elasticity. Dr. 

 Sumpner wished to know if any data as to the relative torsional 

 rigidity of silvered and unsilvered fibres had been obtained, and 

 if the electric resistance of silvered fibres had been determined. 

 Mr. Watson said silvered fibres had been successfully used in 

 electrometers. As regards their torsion, he had found it differ 

 from day to day, and the resistance varied enormously. In reply 

 to question. Prof. Boys described the exact process of soldering 

 the coppered fibre to the tags. As to the torsion of silvered 

 fibres, he would not expect much increase, as the film was very 

 thin. He also thought the elasticity would not be destroyed, 

 for silver and gold make very good torsion wires. — Mr. Little- 

 wood read a note on a method of determining refractive indices, 

 particularly well adapted for either homogeneous or heterogeneous 

 liquids. A vertical scale stands in the liquid contained in a 

 vessel open at the top, and two marks on the part of the scale 

 below the liquid are observed in succession through an inclined 

 telescope capable of moving horizontally parallel to itself along 

 a graduated bar. The horizontal distance between the two 

 positions of the telescope in which the two divisions on the 

 vertical scale are sighted is noticed, and the corresponding 

 distance between the sighted position of two marks on the part of 

 the scale above the liquid determined. When the length between 

 the two marks on the scale in air is equal to that between those 

 in the liquid, the ratio of the corresponding horizontal distances 

 moved through by the telescope gives the index of refraction of 

 a uniform liquid. For liquids in which the density varies in a 

 vertical direction, observations of several points on the scale m 

 the liquid enable the curved path of the light in the liquid to be 

 traced out with considerable accuracy. The accuracy of the 

 laws of diffusion might be tested in this way. The President 

 said the method described was a novel and interesting way of 

 picking out the layers of liquid of different refracting power. | 

 Chemical Society, February 15. — Dr. Armstrong, Presi- 

 dent, in the chair. — The following papers were read :— The 



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