444 



NA TURE 



\JVIarcli 6, i: 



occurred at I»chia on July 2S, 1883, by Prof. A. Serpieri. — On 

 numbers irreducible by complex numbers, by Prof. C. Formenti. 

 — On some forms of right lines produced by two reciprocal star';, 

 by Prof. F. Aschieri. — Meteorological observations mide at the 

 Brera Observatory, Milan, during the months of October and 

 November, 1SS3. 



SOCIETIES AND ACADEMIES 



London 



Royal Society, February 14.—" On a New Reflecting Gal- 

 vanometer of Great Sensibility, and on New Forms of Astatic 

 Galvanometers." By Thomas Gray, B.Sc, F.R.S.E., and 

 Andrew Gray, M.A., F.R.S.E. Communicated by Sir William 

 Thomson, F.R.S. 



The paper describes first a very sensitive galvanometer, of 

 novel construction, which the authors have had made, with aid 

 from the Government Research Fund, for tlieir experiments on 

 the electric resistance of glass and allied substances. It consist^ 

 of two pairs of coils with hollow core;, arranged so that the 

 axes of each pair are parallel and in a vertical plane, which act 

 on a needle-system, consisting of two horse-shoe magnets of 

 thin steel wire connected by a very light frame of aluminium, 

 and hung with their planes vertical, so that a horse-shoe corre- 

 sponds to each pair of coils and has its poles within the hollow 

 cores. In the instrument constructed each pair of coils is carried 

 by a vertical brass plate, and these two plates are set so as to 

 make an angle with one another of aliout 106'. A line drawn 

 from the suspension thread (a single fibre of silk) to a point near 

 a pole of either of the needles, when the needles are at the same 

 distance within both pairs of coils, is nearly at right angles to 

 the axis of the coil, and the motion of the needle for small 

 deflections is nearly along the axis. The needles enter the coils 

 from the same side, and ihe current is usually sent through the 

 coils, so that one pair cau-e their horse-shoe to move outwards 

 and the other pair their horse-shoe to move inwards, thus turn- 

 ing the needle-system round the suspen-ion fibre. A mirror 

 fixed to the aluminium connecting-bar gives a measure of the 

 deflection in the ordinary manner. This system of needles, 

 when rightly adjusted, is practically astatic in a magnetic field of 

 uniform intensity. 



A magnet (or system of magnets) is generally arranged to give 

 a differential field at the upper and lower ends of the needles, 

 which are usually placed with unlike poles turned in similar 

 directions ; but any magnetic system may be employed to give 

 directive force in the projier manner and degree for a particular 

 purpose or arranijement. 



Another form of the instrument is described in which the coils 

 are all in one plane, and the connecting aluminium bar carrying 

 the horse-shoe ne-^dles passes through the plate in which the coil, 

 are set from one side to the other, so that one horse shoe enters 

 its pair of coils from one side, and the other horse-shoe from the 

 other side. When the needle-system is deflected thus, both 

 needles are pushed out of the coils or both pulled in. 



By the method of arranging the needles and coils adopted in 

 these instruments the current is made, when the hollow cores 

 are made small, to act very advantageously on the needles, and 

 hence in great measure their high sensibility. By attaching to 

 the suspended system a small needle to give directive force in a 

 uniform field, the great magnetic moment and leverage of the 

 horseshoes may be taken advantage of. 



The paper then describes a new and very compact form of dis- 

 tributing plite, by means of which a multiple coil galvanometer, 

 or one in which the coil is wound in section;, may be connected 

 in any desired manner to vary its resistance or its sensibility. 



Finally, two forms of instrument are described, in which two 

 perfectly vertical and straight needles connected together rigidly by 

 bars of aluminium are u ed to give a perfectly astatic system, not 

 disturbed by the magnetising or demagnetising action of neighbour- 

 ing magnets, a result the authors think practically unattainable 

 in any arrangement of horizontal needles. Two vertical needles, 

 with their upper ends in the position occupied by the upper 

 needle of a so-called astatic galvanometer, and their lower ends 

 in the position of the lower needle, experience, if their like poles 

 are turned in dissimilar directions, a similar electromagnetic 

 action to that in the horizontal needles ; and the authors pro- 

 pose when convenient to use such an arranjement instead of the 

 ordinary needle sy^tem. 



Also a pair of vertical needles may be used instead of the 

 horse-shoe needles described above, the coils being so placed as 



to act advant.ageously, and give a convenient arrangement of the 

 parts of the instrument. 



Geological Society, February 15. — Annual General Meet- 

 ing.— J. \V. Hnlke, F.R.S. , president, in the chair. — The 

 Secretaries read the Reports of the Council and of the Library 

 and Museum Committee for the year 1883. In the former the 

 Council congratulated the Fellows upon an improvement in the 

 state of the Society's affairs since the date of their last Report, 

 the income of the Society having been greater, and its expendi- 

 ture less, in 18S3 than in 1882, while, although the removal from 

 the list of the names of twelve Fellows whose addresses were 

 unknown, and whose election dated back before the incorporation 

 of the Society in 1826, had produced an apparent loss of three 

 Fellows during the year, the Society might really be regarded 

 as having received an increase of nine Fellows. The increase 

 in the number of contributing Fellows was twenty-two. The 

 Council's Report further announced the awards of the various 

 Medals and of the proceeds of the Donation Funds in the gift 

 of the Society. 



In presenting the Wollaston Gold Medal to Prof. A. Gaudry, 

 F.MjG.S., the President addressed him as follows : — " Prof. A. 

 Gaudry, — The Council of the Geological Society has awarded 

 you the Wollaston Medal in recognition of the value of your 

 pateontological researches and the important scientific gene 

 ralisations you have deduced from long and laborious observa- 

 tions. The numerous paper.; on topographical geology and on 

 palcEontology you have contributed during the past thirty years, 

 your important ' Recherches Scientifiques en Orient entreprises 

 par les ordres du Gouvernement pendant les annees 1853-1854,' 

 your ' Animaux fossiles et geolo ;ie de I'Attique,' and, lastly, 

 your work ' Les Enchainements du monde animal dans les 

 temps geologiques,' have made your name so familiar, wherever 

 our branch of natural science is cultivated, that in receiving you 

 we feel we are not receiving a stranger, but a scientific brother, 

 and one w-ho, by his labours and singleness of aim, has achieved 

 a position as a palaeontologist such as few can hope to attain. 

 Per.-onally it affords me great and sincere pleasure that it has 

 fallen to my lot to hand you this medal, which, by the consent 

 of all, has never been more worthily bestowed." 



The President then presented the balance of the proceeds of 

 the Wolhston Donation Fund to Mr. E. Tulley Newton, F.G.S., 

 and addres.sed him as follows : — "Mr. Newton, — The Council 

 has voted you the balance of the proceeds of the Wollaston 

 Donation Fund, in recognition of the value of your researches 

 amongst the Pleistocene Mammalia of Great Britain, and to 

 assist you in the prosecution of further investigations. Your 

 memoirs published by the Geological Survey of England and 

 Wales, ' On the Vertebrata of the Forest-bed Series of Norfolk 

 and Suffolk,' and on ' The Chimiieroid Fishes of the Cretaceous 

 Rocks,' and your papers published in our y(7!<r«(r/ are considered 

 by the Council to evince great merit ; they regard them as a 

 bright earnest of future work which they hope rray be promoted 

 by this award." 



In presenting the Murchison Medal to Dr. Henry Woodward, 

 F.R.S., the President said: "Dr. Henry Woodward, — The 

 Council has awarded you the Murchison Medal and a grant of 

 ten guineas in recognition of your valu.able researches into the 

 structure and classification of the fossil Crustacea, especially of 

 the Merostomata and Trilobita, and your services to the progress 

 of geology in Great Britain by your conduct of the Geological 

 Magazine for nearly twenty years. Your monograph on the 

 'Merostomata,' published by the Palseontographical Society, and 

 your 'Catalogue of British Fossil Crustacea, with their 

 synonyms and the range in time of each genus and order,' will 

 long continue to be works of reference indispensalile to every 

 student of these interesting life-forms. But valuable as are these 

 written records, they discover but a small part of the services 

 you have rendered in the advancement of our science. How 

 much more you have done by the assistance you have so freely 

 given to all who have sought your help at the Museum in de- 

 ciphering some diflicult matters in palaeontology will never be 

 fully known." 



1 he President then handed the balance of the proceeds of the 

 Murchison Geological Fund to Mr. R. Etberidge, F.R.S., for 

 transmission to Mr. Martin Simpson, of Whitby, and addressed 

 him as f dlows : " Mr. Etheridge, — The balance of the proceeds 

 of the Murchison Donation Fund has been awarded by the 

 Council to Mr. M. Simpson, Curator of the Whitby Museum. 

 He has devoted much attention to the fossils of that district, and 

 he is the author of two b )oks descriptive of them. The Council 



