Feb. 7, 1878] 



NATURE 



295 



larger fragments in the breccias were examined, and referred in 

 part to devitrified trachytes not very rich in silica. The igneous 

 rocks were then described. The syenites of the southern and 

 northern districts were shown probably to belong to one system 

 of intrusion. The hornblendic granite of the Quornden district 

 was also described, and the microscopic structure of the different 

 varieties of it and the above investigated. A number of igneous 

 rocks generally forming dykes in these was described ; some 

 appear to be altered basalts, others andesites, one is a felsite, 

 another a diorite. A group of outlying igneous rocks in the 

 vicinity of Narborough was described. Of these, one is a quartz 

 feltsite with some hornblende ; another varies between this and 

 a quart ziferous syenite j the rest are syenites, and one contains 

 £0 much plagioclase as to be almost a diorite. One of the above, 

 near Enderby, is seen to be distinctly intrusive in an altered slaty 

 rock, which the authors have no doubt belongs to the Forest 

 series. This discovery proves the igneous character of these 

 rocks also, and extends the area of the slaty series five miles 

 further south than was previously known. A section was devoted 

 to the faults of the Forest region. Here the principal fault runs 

 along the anticlinal axis, with a downthrow on its eastern side 

 which diminishes from 2,500 feet at the north end to 500 feet at 

 the south end. East of this the beds seem undisturbed, but on 

 the west they are shattered by many faults, whose course cannot 

 be traced. These are most numerous near Whitwick. The 

 anticlinal fault is pre-carbonifercus. In conclusion, the age of 

 the clastic and of the igneous rocks was discussed. The authors 

 inclined to the opinion that the former are of the same age as 

 the Borrowdale series of the Lake district (lower Silurian), but 

 admitted that the recent discovery of agglomerates in the pre- 

 Cambrian rocks of Wales, and in the probably pre-Cambrian 

 ridges of the Wrekin district, weakens the arguments for this 

 correlation. They do not think that there is any reason for sup- 

 posing them Cambrian. If the Charnwcod series is lower 

 Silurian, they think it most probable that the syenites and the 

 Quornden granite were intruded in some part of the old red sand- 

 stone period, and that the later dykes were very probably post- 

 carboniferous but pre-triassic. 



Meteorological Society, January 16. — Mr. H. S. Eaton, 

 M.A., president, in the chair. — The Council, in their Report, 

 express their gratification at the increase in the number of 

 the Fellows and stations of the Society, the greater size of the 

 Quarterly Journal, and the higher value placed on it by foreign 

 scientific societies, the augmentation of the library, and the 

 addition to the sum hitherto contributed by the Meteorological 

 Council, as well as at other evidences of vigour and progress 

 manifested during the year. The number of Fellows now 

 amounts to 417. The president then delivered his address: — 

 During his tenure of office the alliance between the Meteoro- 

 logical Council and the Society had been further cemented, the 

 Society supplying the Government with certain statistics, and 

 getting some assistance from the Council in return. This arrange- 

 ment had been completely successful, and the president con- 

 sidered it calculated to foster the growth of climatic meteorology 

 under the auspices of the Society, and likely to remove any 

 jealousy on the part of the public towards a governmental 

 department so peculiarly constituted as the Meteorological 

 Council. After criticising some of the work undertaken by the 

 last-mentioned body, Mr. Eaton exhibited curves of the results 

 of the hourly observations of the barometer and thermometer for 

 the year 1876 at Valentia, Armagh, Glasgow, Aberdeen, Fal- 

 mouth, Stonyhurst, and Kew, these being the stations established 

 in 1868 for determining the meteorological constants of the 

 British Isles. The curves showing the combined diurnal and 

 semi-diurnal variation of atmospheric pressure might be referred 

 to one of two distinct types. In one of them the minimum of 

 pressure was most pronounced in the morning, in the other in 

 the afternoon. The former type was found at the maritime 

 stations of Valencia and Falmouth, the latter at inland stations 

 such as Kew. The diurnal range of the temperature of the air 

 was closely related to the pressure. It was least at the maritime 

 stations, reaching only 4° "8 at Falmouth, and attaining a maxi- 

 mum of 9° '3 at Kew. — The following gentlemen were elected 

 Officers and Council for the current year : — President : Charles 

 Greaves, M.Inst. C.E., F.G.S. Vice-Presidents: Henry Storks 

 Eaton, M.A., James Park Harrison, M.A., Robert James 

 Mann, M.D., F.R.A.S., Charles Vincent Walker, F.R.S. 

 Treasurer: Henry Perigal, F.R.A. S. Trustees: Sir Antonio 

 Brady, F.G.S., Stephen WiUiam SUver, F.R.G.S. Secre- 

 taries : George James Symons, John W. Tripe, M.D. Foreign 



Secretary: Robert H. Scott, M.A., F.R.S. Council: Hon. 

 Ralph Abercromby, Arthur Brewin, F.R.A. S., Charles Brooke, 

 F,R.S., Edward Ernest Dymond, William Ellis, F.R,A.S., 

 Rogers Field, B.A., M.Inst.C.E., John Knox Laughton, 

 F.R.A.S., Rev. William Clement Ley, M.A., Richard Strachan, 

 Henry Samuel Tabor, Capt. Henry Toynbee, F.R.A.S., George 

 Mathews Whipple, B.Sc — A resolution was passed to the effect 

 that ladies be admissible as Fellows of the Society. 



Physical Society, January 19. — Prof. G. C.Foster, president 

 in the chair. — The following were elected Members of the 

 Society :— J. Angell, Lieut. G. S. Clarke, R.E., T. F. Iselin, 

 M.A., J. W. Russell, M.A. — Mr. W. H. Preece read a paper 

 on some physical points connected with the telephone. This 

 instrument may be employed both as a source of a new kind of 

 current and as the detector of currents which are incapable of 

 influencing the galvanometer. It shows that the form and 

 duration of Faraday's magneto-electric currents are dependent 

 on the rate and duration of motion of the lines of force pro- 

 ducing them, and that the currents produced by the alteration of 

 a magnetic field vary in strength with the rate of alteration of 

 that field ; and further, that the infinitely small and possibly 

 only molecular movement of the iron plate is suflicient to occa- 

 sion the requisite motion of the lines of force. He pointed out 

 that the telephone explodes the notion that iron takes time to be 

 magnetised and de-magnetised. Mr. R. S. Brough has calcu- 

 lated that the strongest current employed in a telephone is 

 iTTroTrV-iTTruTrth of the C. G. S. unit. Mr. Preece explained that the 

 dimensions of the coil and plate depend on the strength of the 

 magnet, but the former should always consist of fine wire and be 

 made as flat and thin as possible. The adjustment of the 

 position of the magnet (as near as possible to the plate without 

 touching) is easily effected by sounding a vowel sound ah or o 

 clearly and loudly ; a jar is heard when they are too near 

 together. After briefly enumerating the attempts which 

 have been made - to improve the instrument, he mentioned 

 the various purposes to which it can be applied. In 

 addition to being useful in the lecture room, in conjunction with 

 several well-known forms of apparatus, it forms an excellent 

 detector in a Wheatstone bridge for testing short lengths of wire, 

 and condensers can be adjusted by its means with great accuracy. 

 M. Niaudet has shown, by employing a doubly wound coil, 

 that it can be used to detect currents from doubtful sources of 

 electricity, and it is excellent as a means of testing leaky insu- 

 lators. Among the facts already proved by the telephone may 

 be mentioned the existence of currents due to induction in wires 

 contiguous to wires carrying currents, even when these are near 

 each other for only a short distance. Mr. Preece finds that if 

 the telephone wire be inclosed in a conducting sheath which is 

 in connection with the earth, all effects of electric induction are 

 avoided ; and further, if the sheath be of iron, magnetic induc- 

 tion also is avoided, and the telephone acts perfectly. A great 

 number of experiments on the use of the instrument on tele- 

 graphic lines were then described, from which it appears that 

 conversation can be carried on through 100 miles of submarine 

 cable, or 200 miles of a single wire without difficulty, with the 

 instrument as now constructed. The leakage occurring on pole- 

 lines is fatal to its use in wet weather, for distances beyond five 

 miles. An interesting series of telephones was exhibited, and by 

 means of one of very large dimensions Mr. Preece showed that 

 the currents produced by pressing the centre of the plate sensibly 

 affect a Thomson galvanometer, and that the motion of the needle 

 ceases in a remarkably instantaneous manner as soon as the pres- 

 sure is removed, a necessary condition in order that the receiving- 

 plate should accurately reproduce the motions of the sending-plate. 

 In the discussion which followed, Mr. R. Sabine suggested that 

 the failure of all attempts at improving the instrument by 

 increasing its dimensions might be due to the damping action ot 

 the permanent magnet on the plate, the strain on it being pro- 

 portional to the size of magnet and rendering it less sensitive to 

 the sonorous waves. Mr. Coffin pointed out how interesting it 

 would be if, instead of employing a receiving-instrument, the 

 currents could be communicated directly to the auditory nerves, 

 and Prof. Adams explained the relation subsisting between the 

 character of the vibrations of the disc and the character of the 

 electric currents to which they give rise. — Dr. Lodge described 

 a simple form of apparatus for determining the thermal conduc- 

 tivity of rare substances, such as crystals, which cannot be 

 obtained in slabs or rods. It consists of two small tin cans with 

 a copper arm about eight inches long projecting horizontally 

 from each, the external ends being clean and flat. They ar^ 



