480 



NATURE 



{Sept. 28, 1876 



between the friction and the elasticity of different parts it could 

 be made to exhibit very completely the phenomena observed 

 when an electromotive force is made to act (i) between the ends 

 of a metal wire ; (2) through an electrolytic liquid ; (3) in an 

 accumulator with perfectly insulating dielectric ; (4) across a 

 dielectric which is homogeneous, but has a slight conducting 

 power ; (5) across a non-homogeneous or stratified dielectric, 

 in which a " residual charge " is possible. To illustrate in a 

 simple manner the phenomena observed in a submarine cable, 

 the cord might be made elastic. 



Capt. A. W. Baird, R.E., contributed a paper On Tidal 

 Operations in the Gulf of Cutch. — The primary object of the 

 operations was to determine whether secular changes in the level 

 of the land at the head of the gulf, i.e., the " Runn of Cutch," 

 are taking place. Col. Walker at first intended to restrict the 

 observations to a few weeks' duration, but he found that by 

 extending them to a period of a little over a year, scientific 

 results of the highest value would be obtained, and also that this 

 course would be necessary in order to obtain data sufficient to detect 

 minute changes in the relative level of land and sea. The author 

 described the difficulties that had been experienced ; but stated 

 that the whole of the tidal and meteorological observations were 

 in progress of reduction, and when completed were likely to 

 afford results of importance. It was hoped that the effect of 

 the wind and barometer upon the tide might be determined 

 more accurately than had yet been done. Tracings of the actual 

 diagrams were exhibited, and the tidal curves were seen to be 

 very regular and continuous. 



The number of important experiments shown before Section 

 A at this meeting was very remarkable. Besides the experi- 

 ments of Prof. Osborne Reynolds already referred to, there were 

 several others relating to liquids. Prof. James Thomson illus- 

 trated experimentally the origin of the windings of rivers in 

 alluvial plains, as explained in a recent paper in the Royal 

 Society's Proceedings, and Sir William Thomson showed many 

 experiments upon the precessional motion of a spheroidal top 

 filled with liquid. Sir William Thomson also exhibited a new 

 form of astronomical clock with a free pendulum actuated by an 

 independent governor to give approximately correct uniform 

 motion to the escapement- wheel. Mr. H. W. Bosanquet illus- 

 trated experimentally his paper on the conditions of the transfor- 

 mation of pendulum vibrations, and Mr. Colin Brown exhibited 

 his voice harmonium in connection with his paper on just intona- 

 tion. Sir William Thomson explained a method of taking 

 deep-sea soundings in a ship moving at high speed by means of 

 pianoforte- wire and an apparatus which was exhibited and 

 explained. The Rev. J. Ker described an experiment proving 

 rotation of the plane of polarisation of light reflected from a 

 magnetic pole. The attendance throughout was excellent, and 

 the room was generally crowded ; in fact in recent times there 

 has been no meetit g at which so much interest has been taken 

 in the proceedings of this Section. Owing to the number of 

 papers the Section was divided into two on the Monday and Tues- 

 day, and the Section met to finish the work on Wednesday. 

 Saturday was, as usual, devoted to mathematics. There were alto- 

 gether twenty-three mathematical papers, among which may be 

 mentioned those by Prof. Cremona on systems of spheres and 

 systems of lines, by Prof. Tait on two general theorems relating 

 to closed curves, by Mr. J. W. L. Glaisher, giving determmants 

 expressing the number of partitions of a number, and the sum 

 of the divisors of a number ; by Prof. Jung, of Milan, on the 

 inverse problems of the moments of inertia and the moments of 

 resistance of a plane figure, and on a construction for the central 

 nucleus {Centralkern, of Culmann) of a body, and by Mr. G. H. 

 Darwin on graphical interpolation and integration. Two new 

 committees were appointed at the recommendation of Section A, 

 one for commencing experiments upon the elasticity of wires, and 

 the other upon the lunar disturbance of gravity. 



SECTION C— Geology. 



On the Upper Limit of the essentially Marine Beds of the Carbc 

 nijerous System in the British Isles, and the necessity for the 

 establishment of a Middle Carboniferous Group, by Prof. E. Hull, 

 M.A., F.R.A.S. — Prof. Hull distinguished seven stages in the 

 Carboniferous Rocks, each stage being capable of identification 

 by its fossils over large areas in Great Britain and Ireland. 

 These stages are : — 



(i) Upper Coal Measures. 

 (2) Middle Coal Measures. 

 {3) Lower Coal Measures or Gannister Beds. 



(4) Millstone Grit, 



(5) Yoredale Rocks. 



(6) Carboniferous Limestone. 



(7) Lower Limestone Shale. 



He argued that as thirty-three out of fifty-three species of 

 marine shells pass from the Carboniferous Limestone upwards into 

 the Gannister Beds, while only five passed up into the Middle 

 Coal Measures, a palseontological break was indicated of such 

 magnitude as to warrant a more distinct separation of the 

 Gannister Beds from the Middle Coal Measures ; especially as 

 the shells of the former are marine, while many paleontologists 

 regard those of the latter as of fresh- water origin. He therefore 

 proposed to include all from the Gannister Beds to the Yoredale 

 Rocks as Middle Carboniferous ; the term Lower Carboniferous 

 to include as at present the Carboniferous Limestone and Lower 

 Limestone Shale. 



JVote on Sections exhibiting Variation of thickness in the Middle 

 Coal Measures of West Lancashire, by C.E.de Ranee, F.G.S. — The 

 sections described by the author lie between Prescot and Barnsley, 

 where the Middle Coal Measures, containing several thick coal- 

 seams, and the Gannister Beds, containing few important seams, 

 are represented. Having made many sections of the Middle 

 Coal Measures of the district, Mr. de Ranee was satisfied that the 

 amount of the subsidence irom south to north for a distance of 

 ten miles, increased at the rate of about 60 feet per mile, and that 

 the deposition of the Coal Measure strata kept pace with the sub- 

 sidence. 



On the Changes affecting the Southern Extension of the Lowest 

 Carboniferous Rocks, by G. A. Lebour, F.G.S. — The author con- 

 tended for the division of the Carboniferous Rocks into Upper 

 and Lower, drawing the line between the Millstone Grit and 

 Yoredale Series, Dealing with the lower division, it was 

 pointed out that the Upper Old Red Sandstone was in part iden- 

 tical with, or passed upward into Macharen's ' ' Calciferous Sand- 

 stone," known in the North of England as "Tuedian," and in 

 Ireland as " Valentian." In England the upper limit of the 

 " Tuedian'' is equally indefinite, as the series dovetails into the 

 lower members of the "Bernician" Group, in which term the 

 author includes the " Yoredale Series and Calcareous Group in 

 part, Scar Limestone Series and Calcareous Group in part, plus 

 Carljonaceous Group in part." 



On the Mountain Limestone on the West Coast of Sumatra, by 

 Prof. Ferdinand Roemer, of Breslau. — Dr. Verbeck, Director of 

 the Dutch Geological Survey of Sumatra, sent to the author a 

 large collection of fossils from the west coast, for determination 

 and description. The result of this investigation is that the 

 Mountain Limestone is developed on the western coast ot 

 Sumatra, with mineralogical and palseontological characters, very 

 similar to those of the same formation in Europe. The same 

 genera of shells, and partly the same species occur in these widely 

 remote localities. Hitherto the Mountain Limestone has only 

 been known to occur in the Malay Archipelago in Timor, a small 

 but characteristic Mountain Limestone fauna from that island 

 having been described by Prof. Beyrich. It may be expected 

 that by-and-by the Mountain Limestone may be ascertained to 

 have a wider range m the Malay Archipelago than is at present 

 known. From the geographical position of Java, between 

 Sumatra and Timor, it is probable that a zone of Mountain Lime- 

 stone, and perhaps of other palaeozoic rocks, may be found to 

 exist there, although partly hidden by volcanic and tertiary 

 deposits. 



On some Neu, Minerals and on Doubly -refracting Garnets, 

 by Prof, A. von Lasaulx, of Breslau. — Prof, von Lasaubc exhi- 

 bited specimens of a new mineral from Girgenti, Sicily, where 

 it occurs in small cubes on crystals of sulphur and celestine. Its 

 chemical composition is, — silica 86 per cent., water 3 per 

 cent., iron and strontium small quantities, and sulphuric acid, or 

 some acid of the thionic series not yet determined, 7 per cent. 

 From the behaviour of the mineral before the blowpipe, the 

 author named it melanophlogite. The author also described a 

 series of garnets exhibiting the phenomena of double refraction. 



On the Raised Beaches of the Cumberland Coast between White- 

 haven and Boness, by A. Russell, C.E., F.G.S., and T. V. 

 Holmes, F.G.S, — The authors exhibited a map showing several 

 fragments traced by themselves, of raised beaches sloping inland 

 from 25 ft, above the present sea-level to an upper limit of 40 ft. 

 The terraces are covered by low gravel ridges parallel to the old 



