junt 13, 1878] 



NATURE 



i«i 



contraction are spirals, each very nearly at 45° to the 

 length of the tube. 



From the author's early experiments (described in his 

 paper on Electrodynamic Qualities of Metals, published 

 in the Transactions of the Royal Society for 1856), 

 showing a diminution of electric conductivity by puUing 

 force in metallic wires, and Mr. Tomlinson' s recent con- 

 firmations and extensions of those results, it is to be ex- 

 pected that the conductivity of the substance will be less 

 in the direction of extension and greater in the direction 

 of contraction in the stressed substance than the con- 

 ductivity (equal in all directions) of the substance when 

 free from stress. Hence, if an electric current be main- 

 tained along a tube, torsion would cause it to flow in 

 spiral stream-lines, with spirality of opposite name to 

 that of the twist. The whole flow may be resolved into 

 two components : one right along the tube, the other 

 round it. The latter would (like the current through a 

 galvanometer-coil) deflect a needle hung in the interior 

 of the tube with its axis perpendicular to the tube when 

 undisturbed. Or it would magnetise a bar or wire of 

 soft iron placed within the tube. The current itself 

 would (except near the end of the tube) produce no ex- 

 ternal effect directly ; but either of those appliances may 

 be used to give an external indication. 



Since the last meeting of the Physical Society, when 

 the author raised this question of the spiral electric 

 stream lines in a twisted tube, experiments have been 

 made for him by Mr. Macfarlane in the physical laboratory 

 of the University of Glasgow, on the last-mentioned 

 plan; and on the former plan by Mr. J. T. Bottomley in 

 the physical laboratory of King's College, London, by 

 kind permission of Prof. Adams, and with the valuable 

 assistance of his staff. Mr. Macfarlane, using a small 

 mirror magnetometer suspended externally in the neigh- 

 bourhood of one end of an iron wire placed within a 

 brass tube, found that when the twist of the substance 

 was right-handed the end of the wire next that end of the 

 tube by which the current enters becomes a true north pole. 

 Mr. Bottomley, with the cell and suspended mirror and 

 needle of an ordinary dead-beat mirror galvanometer 

 supported by an independent support within a brass tube 

 along which a current is maintained, found that the true 

 north pole of the needle is moved towards the end of the 

 tube by which the current enters. Thus both Mr. Mac- 

 farlane' s and Mr. Bottomley' s observations confirm the 

 anticipation that the electric conductivity is least in the 

 direction of greatest extension, and greatest in the 

 direction of greatest contraction of the metal. The 

 apparatus by which Mr. Bottomley had made his experi- 

 ment was exhibited to the meeting. It included a mode 

 of balancing the effect on the internal needle by placing 

 a circular portion of the main circuit at a proper distance 

 from it, the centre and plane of the circle being in and 

 perpendicular to the axis of the tube. From a measure- 

 ment of the distance from the centre of the circle to the 

 needle, when the balance is obtained, the ratio of the 

 maximum to the minimum conductivity can be cal- 

 culated. 



NOTES 



. We publish a remarkable paper this week, by Mr. J. BIyth, 

 on a new form of the microphone, which needs neither battery 

 nor telephone. The curious importance of Mr. Blyth's inven- 

 tion need not be insisted on. By backing-up the pictures in a 

 drawing-room it might, as has been suggested by a learned 

 professor, be converted into an Ear of Donysiu?, and Horace's 

 words, "suppositos cineri dolose," would come to have an 



.awful meaning. 



' At the Royal Society on Thursday last, all those proposed as 

 new Fellows, and whose names we have already published, were 

 unanimously elected. 



Prof. Simon Newcomb has published as a Supplement to 

 the " American Ephemeris and Nautical Almanac," a few 

 instructions for the observation of the total eclipse of the sun on 

 July 29. The instructions refer to the limits of path of the 

 shadow, instalments, arrangements for observation, the actual 

 observation, search for intra -mercurial planets, drawings of the 

 corona, &c. Prof. Newcomb's paper is accompanied by a series 

 of photolithographic maps of the part of the United States 

 concerned. They include a region extended about 150 miles on 

 each side of the limits of totality. These maps contain certain 

 special features which will render them very useful to observers. 

 For example, on the right-hand side of the track is found, at 

 convenient intervals, the Washington mean time at which the 

 centre of the total phase reaches the several points, where the 

 times are marked. From each of these points a dotted line 

 extends across the path of totality ; this Une is the projection of 

 a diameter of the shadow at the time indicated, so that the 

 middle of the total phase occurs at this time all along the dotted 

 line. These, and other featiures, render these maps of special 

 utility, 



A LETTER has been received in London by Dr. George 

 Bennett, of Sydney, from Signor L. M. D'Albertis, the New 

 Guinea traveller, dated fi"om Sydney, New South Wales, April 

 14, 1878, in which he says, "I have taken my passage in the 

 Caroline, which leaves direct for London on the 1st of May 

 next, and expect to arrive in London about Jmie 15, when I 

 hope to see you. It is my intention to bring all my ethnological 

 and other collections of natural history with me." 



A LABORATORY for the study of marine zoology, in connec- 

 tion with the biological department of the Johns Hopkins Uni- 

 versity, will be organised this summer at Fort Wool, about a 

 mile from Old Point Comfort, Va. The fort contains commo- 

 dious buildings for laboratories and dormitories. The necessary 

 apparatus for collecting and studying marine animals, nets, 

 dredges, microscopes, reagents, aquaria, tables, &c., as well as 

 a small scientific library, will be provided by the University. 

 Through the kindness of the Maryland Commissioner of Fish 

 and Fisheries, the boats used by the Commission will be at the 

 service of the laboratory. The laboratory is organised mainly 

 with a view to the wants of advanced scientific investigators, and 

 there will be no formal courses of lectures. There will, how- 

 ever, be accommodation for a few less advanced students, and 

 suitable instmction will be furnished to meet their individual 

 needs. 



Botanists will be gratified to learn that the publication by 

 Prof. Asa Gray of his great work upon the "Flora of North 

 America " has been commenced, and will be continued as rapidly 

 as practicable. Many years ago a work with the same tide was 

 started by Drs. Torrey and Gray and carried through the Com- 

 positze, where it stopped. The vast extension of the field of 

 American botany, consequent upon the discoveries in California, 

 Oregon, and other regions west of the Mississippi, has made the 

 want of a manual extremely imperative, and this will be furnished 

 by the work referred to. For the purpose of better satisfying 

 the wants of students the work begins with the Gamopetalse 

 irmnediately following the Compositse, and the ground covered 

 by the original " Flora " will be taken up after the other orders 

 are completed. The entire work will consist of two volumes of 

 about 1,200 pages each, the first part, now issued, embracing 

 about 400 pages. The book is to be had from the curator of the 

 Harvard Herbarium at Cambridge. 



The Japanese Government, which is making such rapid 

 strides towards modern civilisation, has just awakened to the 

 necessity of preserving its forests, and stringent regulations have 

 been passed, which shall not only hinder the too rapid destnic- 

 tion of the forests, but increase the area covered by woodlands. 



